Imported Upstream version 0.26.0

[libgit2.git] / src / checkout.c

/*
 * Copyright (C) the libgit2 contributors. All rights reserved.
 *
 * This file is part of libgit2, distributed under the GNU GPL v2 with
 * a Linking Exception. For full terms see the included COPYING file.
 */

#include <assert.h>

#include "checkout.h"

#include "git2/repository.h"
#include "git2/refs.h"
#include "git2/tree.h"
#include "git2/blob.h"
#include "git2/config.h"
#include "git2/diff.h"
#include "git2/submodule.h"
#include "git2/sys/index.h"
#include "git2/sys/filter.h"
#include "git2/merge.h"

#include "refs.h"
#include "repository.h"
#include "index.h"
#include "filter.h"
#include "blob.h"
#include "diff.h"
#include "diff_generate.h"
#include "pathspec.h"
#include "buf_text.h"
#include "diff_xdiff.h"
#include "path.h"
#include "attr.h"
#include "pool.h"
#include "strmap.h"

/* See docs/checkout-internals.md for more information */

enum {
        CHECKOUT_ACTION__NONE = 0,
        CHECKOUT_ACTION__REMOVE = 1,
        CHECKOUT_ACTION__UPDATE_BLOB = 2,
        CHECKOUT_ACTION__UPDATE_SUBMODULE = 4,
        CHECKOUT_ACTION__CONFLICT = 8,
        CHECKOUT_ACTION__REMOVE_CONFLICT = 16,
        CHECKOUT_ACTION__UPDATE_CONFLICT = 32,
        CHECKOUT_ACTION__MAX = 32,
        CHECKOUT_ACTION__DEFER_REMOVE = 64,
        CHECKOUT_ACTION__REMOVE_AND_UPDATE =
                (CHECKOUT_ACTION__UPDATE_BLOB | CHECKOUT_ACTION__REMOVE),
};

typedef struct {
        git_repository *repo;
        git_iterator *target;
        git_diff *diff;
        git_checkout_options opts;
        bool opts_free_baseline;
        char *pfx;
        git_index *index;
        git_pool pool;
        git_vector removes;
        git_vector remove_conflicts;
        git_vector update_conflicts;
        git_vector *update_reuc;
        git_vector *update_names;
        git_buf target_path;
        size_t target_len;
        git_buf tmp;
        unsigned int strategy;
        int can_symlink;
        bool reload_submodules;
        size_t total_steps;
        size_t completed_steps;
        git_checkout_perfdata perfdata;
        git_strmap *mkdir_map;
        git_attr_session attr_session;
} checkout_data;

typedef struct {
        const git_index_entry *ancestor;
        const git_index_entry *ours;
        const git_index_entry *theirs;

        int name_collision:1,
                directoryfile:1,
                one_to_two:1,
                binary:1,
                submodule:1;
} checkout_conflictdata;

static int checkout_notify(
        checkout_data *data,
        git_checkout_notify_t why,
        const git_diff_delta *delta,
        const git_index_entry *wditem)
{
        git_diff_file wdfile;
        const git_diff_file *baseline = NULL, *target = NULL, *workdir = NULL;
        const char *path = NULL;

        if (!data->opts.notify_cb ||
                (why & data->opts.notify_flags) == 0)
                return 0;

        if (wditem) {
                memset(&wdfile, 0, sizeof(wdfile));

                git_oid_cpy(&wdfile.id, &wditem->id);
                wdfile.path = wditem->path;
                wdfile.size = wditem->file_size;
                wdfile.flags = GIT_DIFF_FLAG_VALID_ID;
                wdfile.mode = wditem->mode;

                workdir = &wdfile;

                path = wditem->path;
        }

        if (delta) {
                switch (delta->status) {
                case GIT_DELTA_UNMODIFIED:
                case GIT_DELTA_MODIFIED:
                case GIT_DELTA_TYPECHANGE:
                default:
                        baseline = &delta->old_file;
                        target = &delta->new_file;
                        break;
                case GIT_DELTA_ADDED:
                case GIT_DELTA_IGNORED:
                case GIT_DELTA_UNTRACKED:
                case GIT_DELTA_UNREADABLE:
                        target = &delta->new_file;
                        break;
                case GIT_DELTA_DELETED:
                        baseline = &delta->old_file;
                        break;
                }

                path = delta->old_file.path;
        }

        {
                int error = data->opts.notify_cb(
                        why, path, baseline, target, workdir, data->opts.notify_payload);

                return giterr_set_after_callback_function(
                        error, "git_checkout notification");
        }
}

GIT_INLINE(bool) is_workdir_base_or_new(
        const git_oid *workdir_id,
        const git_diff_file *baseitem,
        const git_diff_file *newitem)
{
        return (git_oid__cmp(&baseitem->id, workdir_id) == 0 ||
                git_oid__cmp(&newitem->id, workdir_id) == 0);
}

static bool checkout_is_workdir_modified(
        checkout_data *data,
        const git_diff_file *baseitem,
        const git_diff_file *newitem,
        const git_index_entry *wditem)
{
        git_oid oid;
        const git_index_entry *ie;

        /* handle "modified" submodule */
        if (wditem->mode == GIT_FILEMODE_COMMIT) {
                git_submodule *sm;
                unsigned int sm_status = 0;
                const git_oid *sm_oid = NULL;
                bool rval = false;

                if (git_submodule_lookup(&sm, data->repo, wditem->path) < 0) {
                        giterr_clear();
                        return true;
                }

                if (git_submodule_status(&sm_status, data->repo, wditem->path, GIT_SUBMODULE_IGNORE_UNSPECIFIED) < 0 ||
                        GIT_SUBMODULE_STATUS_IS_WD_DIRTY(sm_status))
                        rval = true;
                else if ((sm_oid = git_submodule_wd_id(sm)) == NULL)
                        rval = false;
                else
                        rval = (git_oid__cmp(&baseitem->id, sm_oid) != 0);

                git_submodule_free(sm);
                return rval;
        }

        /* Look at the cache to decide if the workdir is modified.  If not,
         * we can simply compare the oid in the cache to the baseitem instead
         * of hashing the file.  If so, we allow the checkout to proceed if the
         * oid is identical (ie, the staged item is what we're trying to check
         * out.)
         */
        if ((ie = git_index_get_bypath(data->index, wditem->path, 0)) != NULL) {
                if (git_index_time_eq(&wditem->mtime, &ie->mtime) &&
                        wditem->file_size == ie->file_size)
                        return !is_workdir_base_or_new(&ie->id, baseitem, newitem);
        }

        /* depending on where base is coming from, we may or may not know
         * the actual size of the data, so we can't rely on this shortcut.
         */
        if (baseitem->size && wditem->file_size != baseitem->size)
                return true;

        /* if the workdir item is a directory, it cannot be a modified file */
        if (S_ISDIR(wditem->mode))
                return false;

        if (git_diff__oid_for_entry(&oid, data->diff, wditem, wditem->mode, NULL) < 0)
                return false;

        /* Allow the checkout if the workdir is not modified *or* if the checkout
         * target's contents are already in the working directory.
         */
        return !is_workdir_base_or_new(&oid, baseitem, newitem);
}

#define CHECKOUT_ACTION_IF(FLAG,YES,NO) \
        ((data->strategy & GIT_CHECKOUT_##FLAG) ? CHECKOUT_ACTION__##YES : CHECKOUT_ACTION__##NO)

static int checkout_action_common(
        int *action,
        checkout_data *data,
        const git_diff_delta *delta,
        const git_index_entry *wd)
{
        git_checkout_notify_t notify = GIT_CHECKOUT_NOTIFY_NONE;

        if ((data->strategy & GIT_CHECKOUT_UPDATE_ONLY) != 0)
                *action = (*action & ~CHECKOUT_ACTION__REMOVE);

        if ((*action & CHECKOUT_ACTION__UPDATE_BLOB) != 0) {
                if (S_ISGITLINK(delta->new_file.mode))
                        *action = (*action & ~CHECKOUT_ACTION__UPDATE_BLOB) |
                                CHECKOUT_ACTION__UPDATE_SUBMODULE;

                /* to "update" a symlink, we must remove the old one first */
                if (delta->new_file.mode == GIT_FILEMODE_LINK && wd != NULL)
                        *action |= CHECKOUT_ACTION__REMOVE;

                /* if the file is on disk and doesn't match our mode, force update */
                if (wd &&
                        GIT_PERMS_IS_EXEC(wd->mode) !=
                        GIT_PERMS_IS_EXEC(delta->new_file.mode))
                                *action |= CHECKOUT_ACTION__REMOVE;

                notify = GIT_CHECKOUT_NOTIFY_UPDATED;
        }

        if ((*action & CHECKOUT_ACTION__CONFLICT) != 0)
                notify = GIT_CHECKOUT_NOTIFY_CONFLICT;

        return checkout_notify(data, notify, delta, wd);
}

static int checkout_action_no_wd(
        int *action,
        checkout_data *data,
        const git_diff_delta *delta)
{
        int error = 0;

        *action = CHECKOUT_ACTION__NONE;

        switch (delta->status) {
        case GIT_DELTA_UNMODIFIED: /* case 12 */
                error = checkout_notify(data, GIT_CHECKOUT_NOTIFY_DIRTY, delta, NULL);
                if (error)
                        return error;
                *action = CHECKOUT_ACTION_IF(RECREATE_MISSING, UPDATE_BLOB, NONE);
                break;
        case GIT_DELTA_ADDED:    /* case 2 or 28 (and 5 but not really) */
                *action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
                break;
        case GIT_DELTA_MODIFIED: /* case 13 (and 35 but not really) */
                *action = CHECKOUT_ACTION_IF(RECREATE_MISSING, UPDATE_BLOB, CONFLICT);
                break;
        case GIT_DELTA_TYPECHANGE: /* case 21 (B->T) and 28 (T->B)*/
                if (delta->new_file.mode == GIT_FILEMODE_TREE)
                        *action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
                break;
        case GIT_DELTA_DELETED: /* case 8 or 25 */
                *action = CHECKOUT_ACTION_IF(SAFE, REMOVE, NONE);
                break;
        default: /* impossible */
                break;
        }

        return checkout_action_common(action, data, delta, NULL);
}

static int checkout_target_fullpath(
        git_buf **out, checkout_data *data, const char *path)
{
        git_buf_truncate(&data->target_path, data->target_len);

        if (path && git_buf_puts(&data->target_path, path) < 0)
                return -1;

        *out = &data->target_path;

        return 0;
}

static bool wd_item_is_removable(
        checkout_data *data, const git_index_entry *wd)
{
        git_buf *full;

        if (wd->mode != GIT_FILEMODE_TREE)
                return true;

        if (checkout_target_fullpath(&full, data, wd->path) < 0)
                return false;

        return !full || !git_path_contains(full, DOT_GIT);
}

static int checkout_queue_remove(checkout_data *data, const char *path)
{
        char *copy = git_pool_strdup(&data->pool, path);
        GITERR_CHECK_ALLOC(copy);
        return git_vector_insert(&data->removes, copy);
}

/* note that this advances the iterator over the wd item */
static int checkout_action_wd_only(
        checkout_data *data,
        git_iterator *workdir,
        const git_index_entry **wditem,
        git_vector *pathspec)
{
        int error = 0;
        bool remove = false;
        git_checkout_notify_t notify = GIT_CHECKOUT_NOTIFY_NONE;
        const git_index_entry *wd = *wditem;

        if (!git_pathspec__match(
                        pathspec, wd->path,
                        (data->strategy & GIT_CHECKOUT_DISABLE_PATHSPEC_MATCH) != 0,
                        git_iterator_ignore_case(workdir), NULL, NULL))
                return git_iterator_advance(wditem, workdir);

        /* check if item is tracked in the index but not in the checkout diff */
        if (data->index != NULL) {
                size_t pos;

                error = git_index__find_pos(
                        &pos, data->index, wd->path, 0, GIT_INDEX_STAGE_ANY);

                if (wd->mode != GIT_FILEMODE_TREE) {
                        if (!error) { /* found by git_index__find_pos call */
                                notify = GIT_CHECKOUT_NOTIFY_DIRTY;
                                remove = ((data->strategy & GIT_CHECKOUT_FORCE) != 0);
                        } else if (error != GIT_ENOTFOUND)
                                return error;
                        else
                                error = 0; /* git_index__find_pos does not set error msg */
                } else {
                        /* for tree entries, we have to see if there are any index
                         * entries that are contained inside that tree
                         */
                        const git_index_entry *e = git_index_get_byindex(data->index, pos);

                        if (e != NULL && data->diff->pfxcomp(e->path, wd->path) == 0)
                                return git_iterator_advance_into(wditem, workdir);
                }
        }

        if (notify != GIT_CHECKOUT_NOTIFY_NONE) {
                /* if we found something in the index, notify and advance */
                if ((error = checkout_notify(data, notify, NULL, wd)) != 0)
                        return error;

                if (remove && wd_item_is_removable(data, wd))
                        error = checkout_queue_remove(data, wd->path);

                if (!error)
                        error = git_iterator_advance(wditem, workdir);
        } else {
                /* untracked or ignored - can't know which until we advance through */
                bool over = false, removable = wd_item_is_removable(data, wd);
                git_iterator_status_t untracked_state;

                /* copy the entry for issuing notification callback later */
                git_index_entry saved_wd = *wd;
                git_buf_sets(&data->tmp, wd->path);
                saved_wd.path = data->tmp.ptr;

                error = git_iterator_advance_over(
                        wditem, &untracked_state, workdir);
                if (error == GIT_ITEROVER)
                        over = true;
                else if (error < 0)
                        return error;

                if (untracked_state == GIT_ITERATOR_STATUS_IGNORED) {
                        notify = GIT_CHECKOUT_NOTIFY_IGNORED;
                        remove = ((data->strategy & GIT_CHECKOUT_REMOVE_IGNORED) != 0);
                } else {
                        notify = GIT_CHECKOUT_NOTIFY_UNTRACKED;
                        remove = ((data->strategy & GIT_CHECKOUT_REMOVE_UNTRACKED) != 0);
                }

                if ((error = checkout_notify(data, notify, NULL, &saved_wd)) != 0)
                        return error;

                if (remove && removable)
                        error = checkout_queue_remove(data, saved_wd.path);

                if (!error && over) /* restore ITEROVER if needed */
                        error = GIT_ITEROVER;
        }

        return error;
}

static bool submodule_is_config_only(
        checkout_data *data,
        const char *path)
{
        git_submodule *sm = NULL;
        unsigned int sm_loc = 0;
        bool rval = false;

        if (git_submodule_lookup(&sm, data->repo, path) < 0)
                return true;

        if (git_submodule_location(&sm_loc, sm) < 0 ||
                sm_loc == GIT_SUBMODULE_STATUS_IN_CONFIG)
                rval = true;

        git_submodule_free(sm);

        return rval;
}

static bool checkout_is_empty_dir(checkout_data *data, const char *path)
{
        git_buf *fullpath;

        if (checkout_target_fullpath(&fullpath, data, path) < 0)
                return false;

        return git_path_is_empty_dir(fullpath->ptr);
}

static int checkout_action_with_wd(
        int *action,
        checkout_data *data,
        const git_diff_delta *delta,
        git_iterator *workdir,
        const git_index_entry *wd)
{
        *action = CHECKOUT_ACTION__NONE;

        switch (delta->status) {
        case GIT_DELTA_UNMODIFIED: /* case 14/15 or 33 */
                if (checkout_is_workdir_modified(data, &delta->old_file, &delta->new_file, wd)) {
                        GITERR_CHECK_ERROR(
                                checkout_notify(data, GIT_CHECKOUT_NOTIFY_DIRTY, delta, wd) );
                        *action = CHECKOUT_ACTION_IF(FORCE, UPDATE_BLOB, NONE);
                }
                break;
        case GIT_DELTA_ADDED: /* case 3, 4 or 6 */
                if (git_iterator_current_is_ignored(workdir))
                        *action = CHECKOUT_ACTION_IF(DONT_OVERWRITE_IGNORED, CONFLICT, UPDATE_BLOB);
                else
                        *action = CHECKOUT_ACTION_IF(FORCE, UPDATE_BLOB, CONFLICT);
                break;
        case GIT_DELTA_DELETED: /* case 9 or 10 (or 26 but not really) */
                if (checkout_is_workdir_modified(data, &delta->old_file, &delta->new_file, wd))
                        *action = CHECKOUT_ACTION_IF(FORCE, REMOVE, CONFLICT);
                else
                        *action = CHECKOUT_ACTION_IF(SAFE, REMOVE, NONE);
                break;
        case GIT_DELTA_MODIFIED: /* case 16, 17, 18 (or 36 but not really) */
                if (wd->mode != GIT_FILEMODE_COMMIT &&
                        checkout_is_workdir_modified(data, &delta->old_file, &delta->new_file, wd))
                        *action = CHECKOUT_ACTION_IF(FORCE, UPDATE_BLOB, CONFLICT);
                else
                        *action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
                break;
        case GIT_DELTA_TYPECHANGE: /* case 22, 23, 29, 30 */
                if (delta->old_file.mode == GIT_FILEMODE_TREE) {
                        if (wd->mode == GIT_FILEMODE_TREE)
                                /* either deleting items in old tree will delete the wd dir,
                                 * or we'll get a conflict when we attempt blob update...
                                 */
                                *action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
                        else if (wd->mode == GIT_FILEMODE_COMMIT) {
                                /* workdir is possibly a "phantom" submodule - treat as a
                                 * tree if the only submodule info came from the config
                                 */
                                if (submodule_is_config_only(data, wd->path))
                                        *action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
                                else
                                        *action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
                        } else
                                *action = CHECKOUT_ACTION_IF(FORCE, REMOVE, CONFLICT);
                }
                else if (checkout_is_workdir_modified(data, &delta->old_file, &delta->new_file, wd))
                        *action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
                else
                        *action = CHECKOUT_ACTION_IF(SAFE, REMOVE_AND_UPDATE, NONE);

                /* don't update if the typechange is to a tree */
                if (delta->new_file.mode == GIT_FILEMODE_TREE)
                        *action = (*action & ~CHECKOUT_ACTION__UPDATE_BLOB);
                break;
        default: /* impossible */
                break;
        }

        return checkout_action_common(action, data, delta, wd);
}

static int checkout_action_with_wd_blocker(
        int *action,
        checkout_data *data,
        const git_diff_delta *delta,
        const git_index_entry *wd)
{
        *action = CHECKOUT_ACTION__NONE;

        switch (delta->status) {
        case GIT_DELTA_UNMODIFIED:
                /* should show delta as dirty / deleted */
                GITERR_CHECK_ERROR(
                        checkout_notify(data, GIT_CHECKOUT_NOTIFY_DIRTY, delta, wd) );
                *action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, NONE);
                break;
        case GIT_DELTA_ADDED:
        case GIT_DELTA_MODIFIED:
                *action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
                break;
        case GIT_DELTA_DELETED:
                *action = CHECKOUT_ACTION_IF(FORCE, REMOVE, CONFLICT);
                break;
        case GIT_DELTA_TYPECHANGE:
                /* not 100% certain about this... */
                *action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
                break;
        default: /* impossible */
                break;
        }

        return checkout_action_common(action, data, delta, wd);
}

static int checkout_action_with_wd_dir(
        int *action,
        checkout_data *data,
        const git_diff_delta *delta,
        git_iterator *workdir,
        const git_index_entry *wd)
{
        *action = CHECKOUT_ACTION__NONE;

        switch (delta->status) {
        case GIT_DELTA_UNMODIFIED: /* case 19 or 24 (or 34 but not really) */
                GITERR_CHECK_ERROR(
                        checkout_notify(data, GIT_CHECKOUT_NOTIFY_DIRTY, delta, NULL));
                GITERR_CHECK_ERROR(
                        checkout_notify(data, GIT_CHECKOUT_NOTIFY_UNTRACKED, NULL, wd));
                *action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, NONE);
                break;
        case GIT_DELTA_ADDED:/* case 4 (and 7 for dir) */
        case GIT_DELTA_MODIFIED: /* case 20 (or 37 but not really) */
                if (delta->old_file.mode == GIT_FILEMODE_COMMIT)
                        /* expected submodule (and maybe found one) */;
                else if (delta->new_file.mode != GIT_FILEMODE_TREE)
                        *action = git_iterator_current_is_ignored(workdir) ?
                                CHECKOUT_ACTION_IF(DONT_OVERWRITE_IGNORED, CONFLICT, REMOVE_AND_UPDATE) :
                                CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
                break;
        case GIT_DELTA_DELETED: /* case 11 (and 27 for dir) */
                if (delta->old_file.mode != GIT_FILEMODE_TREE)
                        GITERR_CHECK_ERROR(
                                checkout_notify(data, GIT_CHECKOUT_NOTIFY_UNTRACKED, NULL, wd));
                break;
        case GIT_DELTA_TYPECHANGE: /* case 24 or 31 */
                if (delta->old_file.mode == GIT_FILEMODE_TREE) {
                        /* For typechange from dir, remove dir and add blob, but it is
                         * not safe to remove dir if it contains modified files.
                         * However, safely removing child files will remove the parent
                         * directory if is it left empty, so we can defer removing the
                         * dir and it will succeed if no children are left.
                         */
                        *action = CHECKOUT_ACTION_IF(SAFE, UPDATE_BLOB, NONE);
                }
                else if (delta->new_file.mode != GIT_FILEMODE_TREE)
                        /* For typechange to dir, dir is already created so no action */
                        *action = CHECKOUT_ACTION_IF(FORCE, REMOVE_AND_UPDATE, CONFLICT);
                break;
        default: /* impossible */
                break;
        }

        return checkout_action_common(action, data, delta, wd);
}

static int checkout_action_with_wd_dir_empty(
        int *action,
        checkout_data *data,
        const git_diff_delta *delta)
{
        int error = checkout_action_no_wd(action, data, delta);

        /* We can always safely remove an empty directory. */
        if (error == 0 && *action != CHECKOUT_ACTION__NONE)
                *action |= CHECKOUT_ACTION__REMOVE;

        return error;
}

static int checkout_action(
        int *action,
        checkout_data *data,
        git_diff_delta *delta,
        git_iterator *workdir,
        const git_index_entry **wditem,
        git_vector *pathspec)
{
        int cmp = -1, error;
        int (*strcomp)(const char *, const char *) = data->diff->strcomp;
        int (*pfxcomp)(const char *str, const char *pfx) = data->diff->pfxcomp;
        int (*advance)(const git_index_entry **, git_iterator *) = NULL;

        /* move workdir iterator to follow along with deltas */

        while (1) {
                const git_index_entry *wd = *wditem;

                if (!wd)
                        return checkout_action_no_wd(action, data, delta);

                cmp = strcomp(wd->path, delta->old_file.path);

                /* 1. wd before delta ("a/a" before "a/b")
                 * 2. wd prefixes delta & should expand ("a/" before "a/b")
                 * 3. wd prefixes delta & cannot expand ("a/b" before "a/b/c")
                 * 4. wd equals delta ("a/b" and "a/b")
                 * 5. wd after delta & delta prefixes wd ("a/b/c" after "a/b/" or "a/b")
                 * 6. wd after delta ("a/c" after "a/b")
                 */

                if (cmp < 0) {
                        cmp = pfxcomp(delta->old_file.path, wd->path);

                        if (cmp == 0) {
                                if (wd->mode == GIT_FILEMODE_TREE) {
                                        /* case 2 - entry prefixed by workdir tree */
                                        error = git_iterator_advance_into(wditem, workdir);
                                        if (error < 0 && error != GIT_ITEROVER)
                                                goto done;
                                        continue;
                                }

                                /* case 3 maybe - wd contains non-dir where dir expected */
                                if (delta->old_file.path[strlen(wd->path)] == '/') {
                                        error = checkout_action_with_wd_blocker(
                                                action, data, delta, wd);
                                        advance = git_iterator_advance;
                                        goto done;
                                }
                        }

                        /* case 1 - handle wd item (if it matches pathspec) */
                        error = checkout_action_wd_only(data, workdir, wditem, pathspec);
                        if (error && error != GIT_ITEROVER)
                                goto done;
                        continue;
                }

                if (cmp == 0) {
                        /* case 4 */
                        error = checkout_action_with_wd(action, data, delta, workdir, wd);
                        advance = git_iterator_advance;
                        goto done;
                }

                cmp = pfxcomp(wd->path, delta->old_file.path);

                if (cmp == 0) { /* case 5 */
                        if (wd->path[strlen(delta->old_file.path)] != '/')
                                return checkout_action_no_wd(action, data, delta);

                        if (delta->status == GIT_DELTA_TYPECHANGE) {
                                if (delta->old_file.mode == GIT_FILEMODE_TREE) {
                                        error = checkout_action_with_wd(action, data, delta, workdir, wd);
                                        advance = git_iterator_advance_into;
                                        goto done;
                                }

                                if (delta->new_file.mode == GIT_FILEMODE_TREE ||
                                        delta->new_file.mode == GIT_FILEMODE_COMMIT ||
                                        delta->old_file.mode == GIT_FILEMODE_COMMIT)
                                {
                                        error = checkout_action_with_wd(action, data, delta, workdir, wd);
                                        advance = git_iterator_advance;
                                        goto done;
                                }
                        }

                        return checkout_is_empty_dir(data, wd->path) ?
                                checkout_action_with_wd_dir_empty(action, data, delta) :
                                checkout_action_with_wd_dir(action, data, delta, workdir, wd);
                }

                /* case 6 - wd is after delta */
                return checkout_action_no_wd(action, data, delta);
        }

done:
        if (!error && advance != NULL &&
                (error = advance(wditem, workdir)) < 0) {
                *wditem = NULL;
                if (error == GIT_ITEROVER)
                        error = 0;
        }

        return error;
}

static int checkout_remaining_wd_items(
        checkout_data *data,
        git_iterator *workdir,
        const git_index_entry *wd,
        git_vector *spec)
{
        int error = 0;

        while (wd && !error)
                error = checkout_action_wd_only(data, workdir, &wd, spec);

        if (error == GIT_ITEROVER)
                error = 0;

        return error;
}

GIT_INLINE(int) checkout_idxentry_cmp(
        const git_index_entry *a,
        const git_index_entry *b)
{
        if (!a && !b)
                return 0;
        else if (!a && b)
                return -1;
        else if(a && !b)
                return 1;
        else
                return strcmp(a->path, b->path);
}

static int checkout_conflictdata_cmp(const void *a, const void *b)
{
        const checkout_conflictdata *ca = a;
        const checkout_conflictdata *cb = b;
        int diff;

        if ((diff = checkout_idxentry_cmp(ca->ancestor, cb->ancestor)) == 0 &&
                (diff = checkout_idxentry_cmp(ca->ours, cb->theirs)) == 0)
                diff = checkout_idxentry_cmp(ca->theirs, cb->theirs);

        return diff;
}

int checkout_conflictdata_empty(
        const git_vector *conflicts, size_t idx, void *payload)
{
        checkout_conflictdata *conflict;

        GIT_UNUSED(payload);

        if ((conflict = git_vector_get(conflicts, idx)) == NULL)
                return -1;

        if (conflict->ancestor || conflict->ours || conflict->theirs)
                return 0;

        git__free(conflict);
        return 1;
}

GIT_INLINE(bool) conflict_pathspec_match(
        checkout_data *data,
        git_iterator *workdir,
        git_vector *pathspec,
        const git_index_entry *ancestor,
        const git_index_entry *ours,
        const git_index_entry *theirs)
{
        /* if the pathspec matches ours *or* theirs, proceed */
        if (ours && git_pathspec__match(pathspec, ours->path,
                (data->strategy & GIT_CHECKOUT_DISABLE_PATHSPEC_MATCH) != 0,
                git_iterator_ignore_case(workdir), NULL, NULL))
                return true;

        if (theirs && git_pathspec__match(pathspec, theirs->path,
                (data->strategy & GIT_CHECKOUT_DISABLE_PATHSPEC_MATCH) != 0,
                git_iterator_ignore_case(workdir), NULL, NULL))
                return true;

        if (ancestor && git_pathspec__match(pathspec, ancestor->path,
                (data->strategy & GIT_CHECKOUT_DISABLE_PATHSPEC_MATCH) != 0,
                git_iterator_ignore_case(workdir), NULL, NULL))
                return true;

        return false;
}

GIT_INLINE(int) checkout_conflict_detect_submodule(checkout_conflictdata *conflict)
{
        conflict->submodule = ((conflict->ancestor && S_ISGITLINK(conflict->ancestor->mode)) ||
                (conflict->ours && S_ISGITLINK(conflict->ours->mode)) ||
                (conflict->theirs && S_ISGITLINK(conflict->theirs->mode)));
        return 0;
}

GIT_INLINE(int) checkout_conflict_detect_binary(git_repository *repo, checkout_conflictdata *conflict)
{
        git_blob *ancestor_blob = NULL, *our_blob = NULL, *their_blob = NULL;
        int error = 0;

        if (conflict->submodule)
                return 0;

        if (conflict->ancestor) {
                if ((error = git_blob_lookup(&ancestor_blob, repo, &conflict->ancestor->id)) < 0)
                        goto done;

                conflict->binary = git_blob_is_binary(ancestor_blob);
        }

        if (!conflict->binary && conflict->ours) {
                if ((error = git_blob_lookup(&our_blob, repo, &conflict->ours->id)) < 0)
                        goto done;

                conflict->binary = git_blob_is_binary(our_blob);
        }

        if (!conflict->binary && conflict->theirs) {
                if ((error = git_blob_lookup(&their_blob, repo, &conflict->theirs->id)) < 0)
                        goto done;

                conflict->binary = git_blob_is_binary(their_blob);
        }

done:
        git_blob_free(ancestor_blob);
        git_blob_free(our_blob);
        git_blob_free(their_blob);

        return error;
}

static int checkout_conflict_append_update(
        const git_index_entry *ancestor,
        const git_index_entry *ours,
        const git_index_entry *theirs,
        void *payload)
{
        checkout_data *data = payload;
        checkout_conflictdata *conflict;
        int error;

        conflict = git__calloc(1, sizeof(checkout_conflictdata));
        GITERR_CHECK_ALLOC(conflict);

        conflict->ancestor = ancestor;
        conflict->ours = ours;
        conflict->theirs = theirs;

        if ((error = checkout_conflict_detect_submodule(conflict)) < 0 ||
                (error = checkout_conflict_detect_binary(data->repo, conflict)) < 0)
        {
                git__free(conflict);
                return error;
        }

        if (git_vector_insert(&data->update_conflicts, conflict))
                return -1;

        return 0;
}

static int checkout_conflicts_foreach(
        checkout_data *data,
        git_index *index,
        git_iterator *workdir,
        git_vector *pathspec,
        int (*cb)(const git_index_entry *, const git_index_entry *, const git_index_entry *, void *),
        void *payload)
{
        git_index_conflict_iterator *iterator = NULL;
        const git_index_entry *ancestor, *ours, *theirs;
        int error = 0;

        if ((error = git_index_conflict_iterator_new(&iterator, index)) < 0)
                goto done;

        /* Collect the conflicts */
        while ((error = git_index_conflict_next(&ancestor, &ours, &theirs, iterator)) == 0) {
                if (!conflict_pathspec_match(data, workdir, pathspec, ancestor, ours, theirs))
                        continue;

                if ((error = cb(ancestor, ours, theirs, payload)) < 0)
                        goto done;
        }

        if (error == GIT_ITEROVER)
                error = 0;

done:
        git_index_conflict_iterator_free(iterator);

        return error;
}

static int checkout_conflicts_load(checkout_data *data, git_iterator *workdir, git_vector *pathspec)
{
        git_index *index;

        /* Only write conficts from sources that have them: indexes. */
        if ((index = git_iterator_index(data->target)) == NULL)
                return 0;

        data->update_conflicts._cmp = checkout_conflictdata_cmp;

        if (checkout_conflicts_foreach(data, index, workdir, pathspec, checkout_conflict_append_update, data) < 0)
                return -1;

        /* Collect the REUC and NAME entries */
        data->update_reuc = &index->reuc;
        data->update_names = &index->names;

        return 0;
}

GIT_INLINE(int) checkout_conflicts_cmp_entry(
        const char *path,
        const git_index_entry *entry)
{
        return strcmp((const char *)path, entry->path);
}

static int checkout_conflicts_cmp_ancestor(const void *p, const void *c)
{
        const char *path = p;
        const checkout_conflictdata *conflict = c;

        if (!conflict->ancestor)
                return 1;

        return checkout_conflicts_cmp_entry(path, conflict->ancestor);
}

static checkout_conflictdata *checkout_conflicts_search_ancestor(
        checkout_data *data,
        const char *path)
{
        size_t pos;

        if (git_vector_bsearch2(&pos, &data->update_conflicts, checkout_conflicts_cmp_ancestor, path) < 0)
                return NULL;

        return git_vector_get(&data->update_conflicts, pos);
}

static checkout_conflictdata *checkout_conflicts_search_branch(
        checkout_data *data,
        const char *path)
{
        checkout_conflictdata *conflict;
        size_t i;

        git_vector_foreach(&data->update_conflicts, i, conflict) {
                int cmp = -1;

                if (conflict->ancestor)
                        break;

                if (conflict->ours)
                        cmp = checkout_conflicts_cmp_entry(path, conflict->ours);
                else if (conflict->theirs)
                        cmp = checkout_conflicts_cmp_entry(path, conflict->theirs);

                if (cmp == 0)
                        return conflict;
        }

        return NULL;
}

static int checkout_conflicts_load_byname_entry(
        checkout_conflictdata **ancestor_out,
        checkout_conflictdata **ours_out,
        checkout_conflictdata **theirs_out,
        checkout_data *data,
        const git_index_name_entry *name_entry)
{
        checkout_conflictdata *ancestor, *ours = NULL, *theirs = NULL;
        int error = 0;

        *ancestor_out = NULL;
        *ours_out = NULL;
        *theirs_out = NULL;

        if (!name_entry->ancestor) {
                giterr_set(GITERR_INDEX, "a NAME entry exists without an ancestor");
                error = -1;
                goto done;
        }

        if (!name_entry->ours && !name_entry->theirs) {
                giterr_set(GITERR_INDEX, "a NAME entry exists without an ours or theirs");
                error = -1;
                goto done;
        }

        if ((ancestor = checkout_conflicts_search_ancestor(data,
                name_entry->ancestor)) == NULL) {
                giterr_set(GITERR_INDEX,
                        "a NAME entry referenced ancestor entry '%s' which does not exist in the main index",
                        name_entry->ancestor);
                error = -1;
                goto done;
        }

        if (name_entry->ours) {
                if (strcmp(name_entry->ancestor, name_entry->ours) == 0)
                        ours = ancestor;
                else if ((ours = checkout_conflicts_search_branch(data, name_entry->ours)) == NULL ||
                        ours->ours == NULL) {
                        giterr_set(GITERR_INDEX,
                                "a NAME entry referenced our entry '%s' which does not exist in the main index",
                                name_entry->ours);
                        error = -1;
                        goto done;
                }
        }

        if (name_entry->theirs) {
                if (strcmp(name_entry->ancestor, name_entry->theirs) == 0)
                        theirs = ancestor;
                else if (name_entry->ours && strcmp(name_entry->ours, name_entry->theirs) == 0)
                        theirs = ours;
                else if ((theirs = checkout_conflicts_search_branch(data, name_entry->theirs)) == NULL ||
                        theirs->theirs == NULL) {
                        giterr_set(GITERR_INDEX,
                                "a NAME entry referenced their entry '%s' which does not exist in the main index",
                                name_entry->theirs);
                        error = -1;
                        goto done;
                }
        }

        *ancestor_out = ancestor;
        *ours_out = ours;
        *theirs_out = theirs;

done:
        return error;
}

static int checkout_conflicts_coalesce_renames(
        checkout_data *data)
{
        git_index *index;
        const git_index_name_entry *name_entry;
        checkout_conflictdata *ancestor_conflict, *our_conflict, *their_conflict;
        size_t i, names;
        int error = 0;

        if ((index = git_iterator_index(data->target)) == NULL)
                return 0;

        /* Juggle entries based on renames */
        names = git_index_name_entrycount(index);

        for (i = 0; i < names; i++) {
                name_entry = git_index_name_get_byindex(index, i);

                if ((error = checkout_conflicts_load_byname_entry(
                        &ancestor_conflict, &our_conflict, &their_conflict,
                        data, name_entry)) < 0)
                        goto done;

                if (our_conflict && our_conflict != ancestor_conflict) {
                        ancestor_conflict->ours = our_conflict->ours;
                        our_conflict->ours = NULL;

                        if (our_conflict->theirs)
                                our_conflict->name_collision = 1;

                        if (our_conflict->name_collision)
                                ancestor_conflict->name_collision = 1;
                }

                if (their_conflict && their_conflict != ancestor_conflict) {
                        ancestor_conflict->theirs = their_conflict->theirs;
                        their_conflict->theirs = NULL;

                        if (their_conflict->ours)
                                their_conflict->name_collision = 1;

                        if (their_conflict->name_collision)
                                ancestor_conflict->name_collision = 1;
                }

                if (our_conflict && our_conflict != ancestor_conflict &&
                        their_conflict && their_conflict != ancestor_conflict)
                        ancestor_conflict->one_to_two = 1;
        }

        git_vector_remove_matching(
                &data->update_conflicts, checkout_conflictdata_empty, NULL);

done:
        return error;
}

static int checkout_conflicts_mark_directoryfile(
        checkout_data *data)
{
        git_index *index;
        checkout_conflictdata *conflict;
        const git_index_entry *entry;
        size_t i, j, len;
        const char *path;
        int prefixed, error = 0;

        if ((index = git_iterator_index(data->target)) == NULL)
                return 0;

        len = git_index_entrycount(index);

        /* Find d/f conflicts */
        git_vector_foreach(&data->update_conflicts, i, conflict) {
                if ((conflict->ours && conflict->theirs) ||
                        (!conflict->ours && !conflict->theirs))
                        continue;

                path = conflict->ours ?
                        conflict->ours->path : conflict->theirs->path;

                if ((error = git_index_find(&j, index, path)) < 0) {
                        if (error == GIT_ENOTFOUND)
                                giterr_set(GITERR_INDEX,
                                        "index inconsistency, could not find entry for expected conflict '%s'", path);

                        goto done;
                }

                for (; j < len; j++) {
                        if ((entry = git_index_get_byindex(index, j)) == NULL) {
                                giterr_set(GITERR_INDEX,
                                        "index inconsistency, truncated index while loading expected conflict '%s'", path);
                                error = -1;
                                goto done;
                        }

                        prefixed = git_path_equal_or_prefixed(path, entry->path, NULL);

                        if (prefixed == GIT_PATH_EQUAL)
                                continue;

                        if (prefixed == GIT_PATH_PREFIX)
                                conflict->directoryfile = 1;

                        break;
                }
        }

done:
        return error;
}

static int checkout_get_update_conflicts(
        checkout_data *data,
        git_iterator *workdir,
        git_vector *pathspec)
{
        int error = 0;

        if (data->strategy & GIT_CHECKOUT_SKIP_UNMERGED)
                return 0;

        if ((error = checkout_conflicts_load(data, workdir, pathspec)) < 0 ||
                (error = checkout_conflicts_coalesce_renames(data)) < 0 ||
                (error = checkout_conflicts_mark_directoryfile(data)) < 0)
                goto done;

done:
        return error;
}

static int checkout_conflict_append_remove(
        const git_index_entry *ancestor,
        const git_index_entry *ours,
        const git_index_entry *theirs,
        void *payload)
{
        checkout_data *data = payload;
        const char *name;

        assert(ancestor || ours || theirs);

        if (ancestor)
                name = git__strdup(ancestor->path);
        else if (ours)
                name = git__strdup(ours->path);
        else if (theirs)
                name = git__strdup(theirs->path);
        else
                abort();

        GITERR_CHECK_ALLOC(name);

        return git_vector_insert(&data->remove_conflicts, (char *)name);
}

static int checkout_get_remove_conflicts(
        checkout_data *data,
        git_iterator *workdir,
        git_vector *pathspec)
{
        if ((data->strategy & GIT_CHECKOUT_DONT_UPDATE_INDEX) != 0)
                return 0;

        return checkout_conflicts_foreach(data, data->index, workdir, pathspec, checkout_conflict_append_remove, data);
}

static int checkout_verify_paths(
        git_repository *repo,
        int action,
        git_diff_delta *delta)
{
        unsigned int flags = GIT_PATH_REJECT_WORKDIR_DEFAULTS;

        if (action & CHECKOUT_ACTION__REMOVE) {
                if (!git_path_isvalid(repo, delta->old_file.path, flags)) {
                        giterr_set(GITERR_CHECKOUT, "cannot remove invalid path '%s'", delta->old_file.path);
                        return -1;
                }
        }

        if (action & ~CHECKOUT_ACTION__REMOVE) {
                if (!git_path_isvalid(repo, delta->new_file.path, flags)) {
                        giterr_set(GITERR_CHECKOUT, "cannot checkout to invalid path '%s'", delta->new_file.path);
                        return -1;
                }
        }

        return 0;
}

static int checkout_get_actions(
        uint32_t **actions_ptr,
        size_t **counts_ptr,
        checkout_data *data,
        git_iterator *workdir)
{
        int error = 0, act;
        const git_index_entry *wditem;
        git_vector pathspec = GIT_VECTOR_INIT, *deltas;
        git_pool pathpool;
        git_diff_delta *delta;
        size_t i, *counts = NULL;
        uint32_t *actions = NULL;

        git_pool_init(&pathpool, 1);

        if (data->opts.paths.count > 0 &&
                git_pathspec__vinit(&pathspec, &data->opts.paths, &pathpool) < 0)
                return -1;

        if ((error = git_iterator_current(&wditem, workdir)) < 0 &&
                error != GIT_ITEROVER)
                goto fail;

        deltas = &data->diff->deltas;

        *counts_ptr = counts = git__calloc(CHECKOUT_ACTION__MAX+1, sizeof(size_t));
        *actions_ptr = actions = git__calloc(
                deltas->length ? deltas->length : 1, sizeof(uint32_t));
        if (!counts || !actions) {
                error = -1;
                goto fail;
        }

        git_vector_foreach(deltas, i, delta) {
                if ((error = checkout_action(&act, data, delta, workdir, &wditem, &pathspec)) == 0)
                        error = checkout_verify_paths(data->repo, act, delta);

                if (error != 0)
                        goto fail;

                actions[i] = act;

                if (act & CHECKOUT_ACTION__REMOVE)
                        counts[CHECKOUT_ACTION__REMOVE]++;
                if (act & CHECKOUT_ACTION__UPDATE_BLOB)
                        counts[CHECKOUT_ACTION__UPDATE_BLOB]++;
                if (act & CHECKOUT_ACTION__UPDATE_SUBMODULE)
                        counts[CHECKOUT_ACTION__UPDATE_SUBMODULE]++;
                if (act & CHECKOUT_ACTION__CONFLICT)
                        counts[CHECKOUT_ACTION__CONFLICT]++;
        }

        error = checkout_remaining_wd_items(data, workdir, wditem, &pathspec);
        if (error)
                goto fail;

        counts[CHECKOUT_ACTION__REMOVE] += data->removes.length;

        if (counts[CHECKOUT_ACTION__CONFLICT] > 0 &&
                (data->strategy & GIT_CHECKOUT_ALLOW_CONFLICTS) == 0)
        {
                giterr_set(GITERR_CHECKOUT, "%"PRIuZ" %s checkout",
                        counts[CHECKOUT_ACTION__CONFLICT],
                        counts[CHECKOUT_ACTION__CONFLICT] == 1 ?
                        "conflict prevents" : "conflicts prevent");
                error = GIT_ECONFLICT;
                goto fail;
        }


        if ((error = checkout_get_remove_conflicts(data, workdir, &pathspec)) < 0 ||
                (error = checkout_get_update_conflicts(data, workdir, &pathspec)) < 0)
                goto fail;

        counts[CHECKOUT_ACTION__REMOVE_CONFLICT] = git_vector_length(&data->remove_conflicts);
        counts[CHECKOUT_ACTION__UPDATE_CONFLICT] = git_vector_length(&data->update_conflicts);

        git_pathspec__vfree(&pathspec);
        git_pool_clear(&pathpool);

        return 0;

fail:
        *counts_ptr = NULL;
        git__free(counts);
        *actions_ptr = NULL;
        git__free(actions);

        git_pathspec__vfree(&pathspec);
        git_pool_clear(&pathpool);

        return error;
}

static bool should_remove_existing(checkout_data *data)
{
        int ignorecase;

        if (git_repository__cvar(&ignorecase, data->repo, GIT_CVAR_IGNORECASE) < 0) {
                ignorecase = 0;
        }

        return (ignorecase &&
                (data->strategy & GIT_CHECKOUT_DONT_REMOVE_EXISTING) == 0);
}

#define MKDIR_NORMAL \
        GIT_MKDIR_PATH | GIT_MKDIR_VERIFY_DIR
#define MKDIR_REMOVE_EXISTING \
        MKDIR_NORMAL | GIT_MKDIR_REMOVE_FILES | GIT_MKDIR_REMOVE_SYMLINKS

static int checkout_mkdir(
        checkout_data *data,
        const char *path,
        const char *base,
        mode_t mode,
        unsigned int flags)
{
        struct git_futils_mkdir_options mkdir_opts = {0};
        int error;

        mkdir_opts.dir_map = data->mkdir_map;
        mkdir_opts.pool = &data->pool;

        error = git_futils_mkdir_relative(
                path, base, mode, flags, &mkdir_opts);

        data->perfdata.mkdir_calls += mkdir_opts.perfdata.mkdir_calls;
        data->perfdata.stat_calls += mkdir_opts.perfdata.stat_calls;
        data->perfdata.chmod_calls += mkdir_opts.perfdata.chmod_calls;

        return error;
}

static int mkpath2file(
        checkout_data *data, const char *path, unsigned int mode)
{
        struct stat st;
        bool remove_existing = should_remove_existing(data);
        unsigned int flags =
                (remove_existing ? MKDIR_REMOVE_EXISTING : MKDIR_NORMAL) |
                GIT_MKDIR_SKIP_LAST;
        int error;

        if ((error = checkout_mkdir(
                        data, path, data->opts.target_directory, mode, flags)) < 0)
                return error;

        if (remove_existing) {
                data->perfdata.stat_calls++;

                if (p_lstat(path, &st) == 0) {

                        /* Some file, symlink or folder already exists at this name.
                         * We would have removed it in remove_the_old unless we're on
                         * a case inensitive filesystem (or the user has asked us not
                         * to).  Remove the similarly named file to write the new.
                         */
                        error = git_futils_rmdir_r(path, NULL, GIT_RMDIR_REMOVE_FILES);
                } else if (errno != ENOENT) {
                        giterr_set(GITERR_OS, "failed to stat '%s'", path);
                        return GIT_EEXISTS;
                } else {
                        giterr_clear();
                }
        }

        return error;
}

struct checkout_stream {
        git_writestream base;
        const char *path;
        int fd;
        int open;
};

static int checkout_stream_write(
        git_writestream *s, const char *buffer, size_t len)
{
        struct checkout_stream *stream = (struct checkout_stream *)s;
        int ret;

        if ((ret = p_write(stream->fd, buffer, len)) < 0)
                giterr_set(GITERR_OS, "could not write to '%s'", stream->path);

        return ret;
}

static int checkout_stream_close(git_writestream *s)
{
        struct checkout_stream *stream = (struct checkout_stream *)s;
        assert(stream && stream->open);

        stream->open = 0;
        return p_close(stream->fd);
}

static void checkout_stream_free(git_writestream *s)
{
        GIT_UNUSED(s);
}

static int blob_content_to_file(
        checkout_data *data,
        struct stat *st,
        git_blob *blob,
        const char *path,
        const char *hint_path,
        mode_t entry_filemode)
{
        int flags = data->opts.file_open_flags;
        mode_t file_mode = data->opts.file_mode ?
                data->opts.file_mode : entry_filemode;
        git_filter_options filter_opts = GIT_FILTER_OPTIONS_INIT;
        struct checkout_stream writer;
        mode_t mode;
        git_filter_list *fl = NULL;
        int fd;
        int error = 0;

        if (hint_path == NULL)
                hint_path = path;

        if ((error = mkpath2file(data, path, data->opts.dir_mode)) < 0)
                return error;

        if (flags <= 0)
                flags = O_CREAT | O_TRUNC | O_WRONLY;
        if (!(mode = file_mode))
                mode = GIT_FILEMODE_BLOB;

        if ((fd = p_open(path, flags, mode)) < 0) {
                giterr_set(GITERR_OS, "could not open '%s' for writing", path);
                return fd;
        }

        filter_opts.attr_session = &data->attr_session;
        filter_opts.temp_buf = &data->tmp;

        if (!data->opts.disable_filters &&
                (error = git_filter_list__load_ext(
                        &fl, data->repo, blob, hint_path,
                        GIT_FILTER_TO_WORKTREE, &filter_opts))) {
                p_close(fd);
                return error;
        }

        /* setup the writer */
        memset(&writer, 0, sizeof(struct checkout_stream));
        writer.base.write = checkout_stream_write;
        writer.base.close = checkout_stream_close;
        writer.base.free = checkout_stream_free;
        writer.path = path;
        writer.fd = fd;
        writer.open = 1;

        error = git_filter_list_stream_blob(fl, blob, &writer.base);

        assert(writer.open == 0);

        git_filter_list_free(fl);

        if (error < 0)
                return error;

        if (st) {
                data->perfdata.stat_calls++;

                if ((error = p_stat(path, st)) < 0) {
                        giterr_set(GITERR_OS, "failed to stat '%s'", path);
                        return error;
                }

                st->st_mode = entry_filemode;
        }

        return 0;
}

static int blob_content_to_link(
        checkout_data *data,
        struct stat *st,
        git_blob *blob,
        const char *path)
{
        git_buf linktarget = GIT_BUF_INIT;
        int error;

        if ((error = mkpath2file(data, path, data->opts.dir_mode)) < 0)
                return error;

        if ((error = git_blob__getbuf(&linktarget, blob)) < 0)
                return error;

        if (data->can_symlink) {
                if ((error = p_symlink(git_buf_cstr(&linktarget), path)) < 0)
                        giterr_set(GITERR_OS, "could not create symlink %s", path);
        } else {
                error = git_futils_fake_symlink(git_buf_cstr(&linktarget), path);
        }

        if (!error) {
                data->perfdata.stat_calls++;

                if ((error = p_lstat(path, st)) < 0)
                        giterr_set(GITERR_CHECKOUT, "could not stat symlink %s", path);

                st->st_mode = GIT_FILEMODE_LINK;
        }

        git_buf_free(&linktarget);

        return error;
}

static int checkout_update_index(
        checkout_data *data,
        const git_diff_file *file,
        struct stat *st)
{
        git_index_entry entry;

        if (!data->index)
                return 0;

        memset(&entry, 0, sizeof(entry));
        entry.path = (char *)file->path; /* cast to prevent warning */
        git_index_entry__init_from_stat(&entry, st, true);
        git_oid_cpy(&entry.id, &file->id);

        return git_index_add(data->index, &entry);
}

static int checkout_submodule_update_index(
        checkout_data *data,
        const git_diff_file *file)
{
        git_buf *fullpath;
        struct stat st;

        /* update the index unless prevented */
        if ((data->strategy & GIT_CHECKOUT_DONT_UPDATE_INDEX) != 0)
                return 0;

        if (checkout_target_fullpath(&fullpath, data, file->path) < 0)
                return -1;

        data->perfdata.stat_calls++;
        if (p_stat(fullpath->ptr, &st) < 0) {
                giterr_set(
                        GITERR_CHECKOUT, "could not stat submodule %s\n", file->path);
                return GIT_ENOTFOUND;
        }

        st.st_mode = GIT_FILEMODE_COMMIT;

        return checkout_update_index(data, file, &st);
}

static int checkout_submodule(
        checkout_data *data,
        const git_diff_file *file)
{
        bool remove_existing = should_remove_existing(data);
        int error = 0;

        /* Until submodules are supported, UPDATE_ONLY means do nothing here */
        if ((data->strategy & GIT_CHECKOUT_UPDATE_ONLY) != 0)
                return 0;

        if ((error = checkout_mkdir(
                        data,
                        file->path, data->opts.target_directory, data->opts.dir_mode,
                        remove_existing ? MKDIR_REMOVE_EXISTING : MKDIR_NORMAL)) < 0)
                return error;

        if ((error = git_submodule_lookup(NULL, data->repo, file->path)) < 0) {
                /* I've observed repos with submodules in the tree that do not
                 * have a .gitmodules - core Git just makes an empty directory
                 */
                if (error == GIT_ENOTFOUND) {
                        giterr_clear();
                        return checkout_submodule_update_index(data, file);
                }

                return error;
        }

        /* TODO: Support checkout_strategy options.  Two circumstances:
         * 1 - submodule already checked out, but we need to move the HEAD
         *     to the new OID, or
         * 2 - submodule not checked out and we should recursively check it out
         *
         * Checkout will not execute a pull on the submodule, but a clone
         * command should probably be able to.  Do we need a submodule callback?
         */

        return checkout_submodule_update_index(data, file);
}

static void report_progress(
        checkout_data *data,
        const char *path)
{
        if (data->opts.progress_cb)
                data->opts.progress_cb(
                        path, data->completed_steps, data->total_steps,
                        data->opts.progress_payload);
}

static int checkout_safe_for_update_only(
        checkout_data *data, const char *path, mode_t expected_mode)
{
        struct stat st;

        data->perfdata.stat_calls++;

        if (p_lstat(path, &st) < 0) {
                /* if doesn't exist, then no error and no update */
                if (errno == ENOENT || errno == ENOTDIR)
                        return 0;

                /* otherwise, stat error and no update */
                giterr_set(GITERR_OS, "failed to stat '%s'", path);
                return -1;
        }

        /* only safe for update if this is the same type of file */
        if ((st.st_mode & ~0777) == (expected_mode & ~0777))
                return 1;

        return 0;
}

static int checkout_write_content(
        checkout_data *data,
        const git_oid *oid,
        const char *full_path,
        const char *hint_path,
        unsigned int mode,
        struct stat *st)
{
        int error = 0;
        git_blob *blob;

        if ((error = git_blob_lookup(&blob, data->repo, oid)) < 0)
                return error;

        if (S_ISLNK(mode))
                error = blob_content_to_link(data, st, blob, full_path);
        else
                error = blob_content_to_file(data, st, blob, full_path, hint_path, mode);

        git_blob_free(blob);

        /* if we try to create the blob and an existing directory blocks it from
         * being written, then there must have been a typechange conflict in a
         * parent directory - suppress the error and try to continue.
         */
        if ((data->strategy & GIT_CHECKOUT_ALLOW_CONFLICTS) != 0 &&
                (error == GIT_ENOTFOUND || error == GIT_EEXISTS))
        {
                giterr_clear();
                error = 0;
        }

        return error;
}

static int checkout_blob(
        checkout_data *data,
        const git_diff_file *file)
{
        git_buf *fullpath;
        struct stat st;
        int error = 0;

        if (checkout_target_fullpath(&fullpath, data, file->path) < 0)
                return -1;

        if ((data->strategy & GIT_CHECKOUT_UPDATE_ONLY) != 0) {
                int rval = checkout_safe_for_update_only(
                        data, fullpath->ptr, file->mode);

                if (rval <= 0)
                        return rval;
        }

        error = checkout_write_content(
                data, &file->id, fullpath->ptr, NULL, file->mode, &st);

        /* update the index unless prevented */
        if (!error && (data->strategy & GIT_CHECKOUT_DONT_UPDATE_INDEX) == 0)
                error = checkout_update_index(data, file, &st);

        /* update the submodule data if this was a new .gitmodules file */
        if (!error && strcmp(file->path, ".gitmodules") == 0)
                data->reload_submodules = true;

        return error;
}

static int checkout_remove_the_old(
        unsigned int *actions,
        checkout_data *data)
{
        int error = 0;
        git_diff_delta *delta;
        const char *str;
        size_t i;
        git_buf *fullpath;
        uint32_t flg = GIT_RMDIR_EMPTY_PARENTS |
                GIT_RMDIR_REMOVE_FILES | GIT_RMDIR_REMOVE_BLOCKERS;

        if (data->opts.checkout_strategy & GIT_CHECKOUT_SKIP_LOCKED_DIRECTORIES)
                flg |= GIT_RMDIR_SKIP_NONEMPTY;

        if (checkout_target_fullpath(&fullpath, data, NULL) < 0)
                return -1;

        git_vector_foreach(&data->diff->deltas, i, delta) {
                if (actions[i] & CHECKOUT_ACTION__REMOVE) {
                        error = git_futils_rmdir_r(
                                delta->old_file.path, fullpath->ptr, flg);

                        if (error < 0)
                                return error;

                        data->completed_steps++;
                        report_progress(data, delta->old_file.path);

                        if ((actions[i] & CHECKOUT_ACTION__UPDATE_BLOB) == 0 &&
                                (data->strategy & GIT_CHECKOUT_DONT_UPDATE_INDEX) == 0 &&
                                data->index != NULL)
                        {
                                (void)git_index_remove(data->index, delta->old_file.path, 0);
                        }
                }
        }

        git_vector_foreach(&data->removes, i, str) {
                error = git_futils_rmdir_r(str, fullpath->ptr, flg);
                if (error < 0)
                        return error;

                data->completed_steps++;
                report_progress(data, str);

                if ((data->strategy & GIT_CHECKOUT_DONT_UPDATE_INDEX) == 0 &&
                        data->index != NULL)
                {
                        if (str[strlen(str) - 1] == '/')
                                (void)git_index_remove_directory(data->index, str, 0);
                        else
                                (void)git_index_remove(data->index, str, 0);
                }
        }

        return 0;
}

static int checkout_deferred_remove(git_repository *repo, const char *path)
{
#if 0
        int error = git_futils_rmdir_r(
                path, data->opts.target_directory, GIT_RMDIR_EMPTY_PARENTS);

        if (error == GIT_ENOTFOUND) {
                error = 0;
                giterr_clear();
        }

        return error;
#else
        GIT_UNUSED(repo);
        GIT_UNUSED(path);
        assert(false);
        return 0;
#endif
}

static int checkout_create_the_new(
        unsigned int *actions,
        checkout_data *data)
{
        int error = 0;
        git_diff_delta *delta;
        size_t i;

        git_vector_foreach(&data->diff->deltas, i, delta) {
                if (actions[i] & CHECKOUT_ACTION__DEFER_REMOVE) {
                        /* this had a blocker directory that should only be removed iff
                         * all of the contents of the directory were safely removed
                         */
                        if ((error = checkout_deferred_remove(
                                        data->repo, delta->old_file.path)) < 0)
                                return error;
                }

                if (actions[i] & CHECKOUT_ACTION__UPDATE_BLOB) {
                        error = checkout_blob(data, &delta->new_file);
                        if (error < 0)
                                return error;

                        data->completed_steps++;
                        report_progress(data, delta->new_file.path);
                }
        }

        return 0;
}

static int checkout_create_submodules(
        unsigned int *actions,
        checkout_data *data)
{
        int error = 0;
        git_diff_delta *delta;
        size_t i;

        git_vector_foreach(&data->diff->deltas, i, delta) {
                if (actions[i] & CHECKOUT_ACTION__DEFER_REMOVE) {
                        /* this has a blocker directory that should only be removed iff
                         * all of the contents of the directory were safely removed
                         */
                        if ((error = checkout_deferred_remove(
                                        data->repo, delta->old_file.path)) < 0)
                                return error;
                }

                if (actions[i] & CHECKOUT_ACTION__UPDATE_SUBMODULE) {
                        int error = checkout_submodule(data, &delta->new_file);
                        if (error < 0)
                                return error;

                        data->completed_steps++;
                        report_progress(data, delta->new_file.path);
                }
        }

        return 0;
}

static int checkout_lookup_head_tree(git_tree **out, git_repository *repo)
{
        int error = 0;
        git_reference *ref = NULL;
        git_object *head;

        if (!(error = git_repository_head(&ref, repo)) &&
                !(error = git_reference_peel(&head, ref, GIT_OBJ_TREE)))
                *out = (git_tree *)head;

        git_reference_free(ref);

        return error;
}


static int conflict_entry_name(
        git_buf *out,
        const char *side_name,
        const char *filename)
{
        if (git_buf_puts(out, side_name) < 0 ||
                git_buf_putc(out, ':') < 0 ||
                git_buf_puts(out, filename) < 0)
                return -1;

        return 0;
}

static int checkout_path_suffixed(git_buf *path, const char *suffix)
{
        size_t path_len;
        int i = 0, error = 0;

        if ((error = git_buf_putc(path, '~')) < 0 || (error = git_buf_puts(path, suffix)) < 0)
                return -1;

        path_len = git_buf_len(path);

        while (git_path_exists(git_buf_cstr(path)) && i < INT_MAX) {
                git_buf_truncate(path, path_len);

                if ((error = git_buf_putc(path, '_')) < 0 ||
                        (error = git_buf_printf(path, "%d", i)) < 0)
                        return error;

                i++;
        }

        if (i == INT_MAX) {
                git_buf_truncate(path, path_len);

                giterr_set(GITERR_CHECKOUT, "could not write '%s': working directory file exists", path->ptr);
                return GIT_EEXISTS;
        }

        return 0;
}

static int checkout_write_entry(
        checkout_data *data,
        checkout_conflictdata *conflict,
        const git_index_entry *side)
{
        const char *hint_path = NULL, *suffix;
        git_buf *fullpath;
        struct stat st;
        int error;

        assert (side == conflict->ours || side == conflict->theirs);

        if (checkout_target_fullpath(&fullpath, data, side->path) < 0)
                return -1;

        if ((conflict->name_collision || conflict->directoryfile) &&
                (data->strategy & GIT_CHECKOUT_USE_OURS) == 0 &&
                (data->strategy & GIT_CHECKOUT_USE_THEIRS) == 0) {

                if (side == conflict->ours)
                        suffix = data->opts.our_label ? data->opts.our_label :
                                "ours";
                else
                        suffix = data->opts.their_label ? data->opts.their_label :
                                "theirs";

                if (checkout_path_suffixed(fullpath, suffix) < 0)
                        return -1;

                hint_path = side->path;
        }

        if ((data->strategy & GIT_CHECKOUT_UPDATE_ONLY) != 0 &&
                (error = checkout_safe_for_update_only(data, fullpath->ptr, side->mode)) <= 0)
                return error;

        return checkout_write_content(data,
                &side->id, fullpath->ptr, hint_path, side->mode, &st);
}

static int checkout_write_entries(
        checkout_data *data,
        checkout_conflictdata *conflict)
{
        int error = 0;

        if ((error = checkout_write_entry(data, conflict, conflict->ours)) >= 0)
                error = checkout_write_entry(data, conflict, conflict->theirs);

        return error;
}

static int checkout_merge_path(
        git_buf *out,
        checkout_data *data,
        checkout_conflictdata *conflict,
        git_merge_file_result *result)
{
        const char *our_label_raw, *their_label_raw, *suffix;
        int error = 0;

        if ((error = git_buf_joinpath(out, git_repository_workdir(data->repo), result->path)) < 0)
                return error;

        /* Most conflicts simply use the filename in the index */
        if (!conflict->name_collision)
                return 0;

        /* Rename 2->1 conflicts need the branch name appended */
        our_label_raw = data->opts.our_label ? data->opts.our_label : "ours";
        their_label_raw = data->opts.their_label ? data->opts.their_label : "theirs";
        suffix = strcmp(result->path, conflict->ours->path) == 0 ? our_label_raw : their_label_raw;

        if ((error = checkout_path_suffixed(out, suffix)) < 0)
                return error;

        return 0;
}

static int checkout_write_merge(
        checkout_data *data,
        checkout_conflictdata *conflict)
{
        git_buf our_label = GIT_BUF_INIT, their_label = GIT_BUF_INIT,
                path_suffixed = GIT_BUF_INIT, path_workdir = GIT_BUF_INIT,
                in_data = GIT_BUF_INIT, out_data = GIT_BUF_INIT;
        git_merge_file_options opts = GIT_MERGE_FILE_OPTIONS_INIT;
        git_merge_file_result result = {0};
        git_filebuf output = GIT_FILEBUF_INIT;
        git_filter_list *fl = NULL;
        git_filter_options filter_opts = GIT_FILTER_OPTIONS_INIT;
        int error = 0;

        if (data->opts.checkout_strategy & GIT_CHECKOUT_CONFLICT_STYLE_DIFF3)
                opts.flags |= GIT_MERGE_FILE_STYLE_DIFF3;

        opts.ancestor_label = data->opts.ancestor_label ?
                data->opts.ancestor_label : "ancestor";
        opts.our_label = data->opts.our_label ?
                data->opts.our_label : "ours";
        opts.their_label = data->opts.their_label ?
                data->opts.their_label : "theirs";

        /* If all the paths are identical, decorate the diff3 file with the branch
         * names.  Otherwise, append branch_name:path.
         */
        if (conflict->ours && conflict->theirs &&
                strcmp(conflict->ours->path, conflict->theirs->path) != 0) {

                if ((error = conflict_entry_name(
                        &our_label, opts.our_label, conflict->ours->path)) < 0 ||
                        (error = conflict_entry_name(
                        &their_label, opts.their_label, conflict->theirs->path)) < 0)
                        goto done;

                opts.our_label = git_buf_cstr(&our_label);
                opts.their_label = git_buf_cstr(&their_label);
        }

        if ((error = git_merge_file_from_index(&result, data->repo,
                conflict->ancestor, conflict->ours, conflict->theirs, &opts)) < 0)
                goto done;

        if (result.path == NULL || result.mode == 0) {
                giterr_set(GITERR_CHECKOUT, "could not merge contents of file");
                error = GIT_ECONFLICT;
                goto done;
        }

        if ((error = checkout_merge_path(&path_workdir, data, conflict, &result)) < 0)
                goto done;

        if ((data->strategy & GIT_CHECKOUT_UPDATE_ONLY) != 0 &&
                (error = checkout_safe_for_update_only(data, git_buf_cstr(&path_workdir), result.mode)) <= 0)
                goto done;

        if (!data->opts.disable_filters) {
                in_data.ptr = (char *)result.ptr;
                in_data.size = result.len;

                filter_opts.attr_session = &data->attr_session;
                filter_opts.temp_buf = &data->tmp;

                if ((error = git_filter_list__load_ext(
                                &fl, data->repo, NULL, git_buf_cstr(&path_workdir),
                                GIT_FILTER_TO_WORKTREE, &filter_opts)) < 0 ||
                        (error = git_filter_list_apply_to_data(&out_data, fl, &in_data)) < 0)
                        goto done;
        } else {
                out_data.ptr = (char *)result.ptr;
                out_data.size = result.len;
        }

        if ((error = mkpath2file(data, path_workdir.ptr, data->opts.dir_mode)) < 0 ||
                (error = git_filebuf_open(&output, git_buf_cstr(&path_workdir), GIT_FILEBUF_DO_NOT_BUFFER, result.mode)) < 0 ||
                (error = git_filebuf_write(&output, out_data.ptr, out_data.size)) < 0 ||
                (error = git_filebuf_commit(&output)) < 0)
                goto done;

done:
        git_filter_list_free(fl);

        git_buf_free(&out_data);
        git_buf_free(&our_label);
        git_buf_free(&their_label);

        git_merge_file_result_free(&result);
        git_buf_free(&path_workdir);
        git_buf_free(&path_suffixed);

        return error;
}

static int checkout_conflict_add(
        checkout_data *data,
        const git_index_entry *conflict)
{
        int error = git_index_remove(data->index, conflict->path, 0);

        if (error == GIT_ENOTFOUND)
                giterr_clear();
        else if (error < 0)
                return error;

        return git_index_add(data->index, conflict);
}

static int checkout_conflict_update_index(
        checkout_data *data,
        checkout_conflictdata *conflict)
{
        int error = 0;

        if (conflict->ancestor)
                error = checkout_conflict_add(data, conflict->ancestor);

        if (!error && conflict->ours)
                error = checkout_conflict_add(data, conflict->ours);

        if (!error && conflict->theirs)
                error = checkout_conflict_add(data, conflict->theirs);

        return error;
}

static int checkout_create_conflicts(checkout_data *data)
{
        checkout_conflictdata *conflict;
        size_t i;
        int error = 0;

        git_vector_foreach(&data->update_conflicts, i, conflict) {

                /* Both deleted: nothing to do */
                if (conflict->ours == NULL && conflict->theirs == NULL)
                        error = 0;

                else if ((data->strategy & GIT_CHECKOUT_USE_OURS) &&
                        conflict->ours)
                        error = checkout_write_entry(data, conflict, conflict->ours);
                else if ((data->strategy & GIT_CHECKOUT_USE_THEIRS) &&
                        conflict->theirs)
                        error = checkout_write_entry(data, conflict, conflict->theirs);

                /* Ignore the other side of name collisions. */
                else if ((data->strategy & GIT_CHECKOUT_USE_OURS) &&
                        !conflict->ours && conflict->name_collision)
                        error = 0;
                else if ((data->strategy & GIT_CHECKOUT_USE_THEIRS) &&
                        !conflict->theirs && conflict->name_collision)
                        error = 0;

                /* For modify/delete, name collisions and d/f conflicts, write
                 * the file (potentially with the name mangled.
                 */
                else if (conflict->ours != NULL && conflict->theirs == NULL)
                        error = checkout_write_entry(data, conflict, conflict->ours);
                else if (conflict->ours == NULL && conflict->theirs != NULL)
                        error = checkout_write_entry(data, conflict, conflict->theirs);

                /* Add/add conflicts and rename 1->2 conflicts, write the
                 * ours/theirs sides (potentially name mangled).
                 */
                else if (conflict->one_to_two)
                        error = checkout_write_entries(data, conflict);

                /* If all sides are links, write the ours side */
                else if (S_ISLNK(conflict->ours->mode) &&
                        S_ISLNK(conflict->theirs->mode))
                        error = checkout_write_entry(data, conflict, conflict->ours);
                /* Link/file conflicts, write the file side */
                else if (S_ISLNK(conflict->ours->mode))
                        error = checkout_write_entry(data, conflict, conflict->theirs);
                else if (S_ISLNK(conflict->theirs->mode))
                        error = checkout_write_entry(data, conflict, conflict->ours);

                /* If any side is a gitlink, do nothing. */
                else if (conflict->submodule)
                        error = 0;

                /* If any side is binary, write the ours side */
                else if (conflict->binary)
                        error = checkout_write_entry(data, conflict, conflict->ours);

                else if (!error)
                        error = checkout_write_merge(data, conflict);

                /* Update the index extensions (REUC and NAME) if we're checking
                 * out a different index. (Otherwise just leave them there.)
                 */
                if (!error && (data->strategy & GIT_CHECKOUT_DONT_UPDATE_INDEX) == 0)
                        error = checkout_conflict_update_index(data, conflict);

                if (error)
                        break;

                data->completed_steps++;
                report_progress(data,
                        conflict->ours ? conflict->ours->path :
                        (conflict->theirs ? conflict->theirs->path : conflict->ancestor->path));
        }

        return error;
}

static int checkout_remove_conflicts(checkout_data *data)
{
        const char *conflict;
        size_t i;

        git_vector_foreach(&data->remove_conflicts, i, conflict) {
                if (git_index_conflict_remove(data->index, conflict) < 0)
                        return -1;

                data->completed_steps++;
        }

        return 0;
}

static int checkout_extensions_update_index(checkout_data *data)
{
        const git_index_reuc_entry *reuc_entry;
        const git_index_name_entry *name_entry;
        size_t i;
        int error = 0;

        if ((data->strategy & GIT_CHECKOUT_UPDATE_ONLY) != 0)
                return 0;

        if (data->update_reuc) {
                git_vector_foreach(data->update_reuc, i, reuc_entry) {
                        if ((error = git_index_reuc_add(data->index, reuc_entry->path,
                                reuc_entry->mode[0], &reuc_entry->oid[0],
                                reuc_entry->mode[1], &reuc_entry->oid[1],
                                reuc_entry->mode[2], &reuc_entry->oid[2])) < 0)
                                goto done;
                }
        }

        if (data->update_names) {
                git_vector_foreach(data->update_names, i, name_entry) {
                        if ((error = git_index_name_add(data->index, name_entry->ancestor,
                                name_entry->ours, name_entry->theirs)) < 0)
                                goto done;
                }
        }

done:
        return error;
}

static void checkout_data_clear(checkout_data *data)
{
        if (data->opts_free_baseline) {
                git_tree_free(data->opts.baseline);
                data->opts.baseline = NULL;
        }

        git_vector_free(&data->removes);
        git_pool_clear(&data->pool);

        git_vector_free_deep(&data->remove_conflicts);
        git_vector_free_deep(&data->update_conflicts);

        git__free(data->pfx);
        data->pfx = NULL;

        git_buf_free(&data->target_path);
        git_buf_free(&data->tmp);

        git_index_free(data->index);
        data->index = NULL;

        git_strmap_free(data->mkdir_map);
        data->mkdir_map = NULL;

        git_attr_session__free(&data->attr_session);
}

static int checkout_data_init(
        checkout_data *data,
        git_iterator *target,
        const git_checkout_options *proposed)
{
        int error = 0;
        git_repository *repo = git_iterator_owner(target);

        memset(data, 0, sizeof(*data));

        if (!repo) {
                giterr_set(GITERR_CHECKOUT, "cannot checkout nothing");
                return -1;
        }

        if ((!proposed || !proposed->target_directory) &&
                (error = git_repository__ensure_not_bare(repo, "checkout")) < 0)
                return error;

        data->repo = repo;
        data->target = target;

        GITERR_CHECK_VERSION(
                proposed, GIT_CHECKOUT_OPTIONS_VERSION, "git_checkout_options");

        if (!proposed)
                GIT_INIT_STRUCTURE(&data->opts, GIT_CHECKOUT_OPTIONS_VERSION);
        else
                memmove(&data->opts, proposed, sizeof(git_checkout_options));

        if (!data->opts.target_directory)
                data->opts.target_directory = git_repository_workdir(repo);
        else if (!git_path_isdir(data->opts.target_directory) &&
                         (error = checkout_mkdir(data,
                                data->opts.target_directory, NULL,
                                GIT_DIR_MODE, GIT_MKDIR_VERIFY_DIR)) < 0)
                goto cleanup;

        /* refresh config and index content unless NO_REFRESH is given */
        if ((data->opts.checkout_strategy & GIT_CHECKOUT_NO_REFRESH) == 0) {
                git_config *cfg;

                if ((error = git_repository_config__weakptr(&cfg, repo)) < 0)
                        goto cleanup;

                /* Get the repository index and reload it (unless we're checking
                 * out the index; then it has the changes we're trying to check
                 * out and those should not be overwritten.)
                 */
                if ((error = git_repository_index(&data->index, data->repo)) < 0)
                        goto cleanup;

                if (data->index != git_iterator_index(target)) {
                        if ((error = git_index_read(data->index, true)) < 0)
                                goto cleanup;

                        /* cannot checkout if unresolved conflicts exist */
                        if ((data->opts.checkout_strategy & GIT_CHECKOUT_FORCE) == 0 &&
                                git_index_has_conflicts(data->index)) {
                                error = GIT_ECONFLICT;
                                giterr_set(GITERR_CHECKOUT,
                                        "unresolved conflicts exist in the index");
                                goto cleanup;
                        }

                        /* clean conflict data in the current index */
                        git_index_name_clear(data->index);
                        git_index_reuc_clear(data->index);
                }
        }

        /* if you are forcing, allow all safe updates, plus recreate missing */
        if ((data->opts.checkout_strategy & GIT_CHECKOUT_FORCE) != 0)
                data->opts.checkout_strategy |= GIT_CHECKOUT_SAFE |
                        GIT_CHECKOUT_RECREATE_MISSING;

        /* if the repository does not actually have an index file, then this
         * is an initial checkout (perhaps from clone), so we allow safe updates
         */
        if (!data->index->on_disk &&
                (data->opts.checkout_strategy & GIT_CHECKOUT_SAFE) != 0)
                data->opts.checkout_strategy |= GIT_CHECKOUT_RECREATE_MISSING;

        data->strategy = data->opts.checkout_strategy;

        /* opts->disable_filters is false by default */

        if (!data->opts.dir_mode)
                data->opts.dir_mode = GIT_DIR_MODE;

        if (!data->opts.file_open_flags)
                data->opts.file_open_flags = O_CREAT | O_TRUNC | O_WRONLY;

        data->pfx = git_pathspec_prefix(&data->opts.paths);

        if ((error = git_repository__cvar(
                         &data->can_symlink, repo, GIT_CVAR_SYMLINKS)) < 0)
                goto cleanup;

        if (!data->opts.baseline && !data->opts.baseline_index) {
                data->opts_free_baseline = true;
                error = 0;

                /* if we don't have an index, this is an initial checkout and
                 * should be against an empty baseline
                 */
                if (data->index->on_disk)
                        error = checkout_lookup_head_tree(&data->opts.baseline, repo);

                if (error == GIT_EUNBORNBRANCH) {
                        error = 0;
                        giterr_clear();
                }

                if (error < 0)
                        goto cleanup;
        }

        if ((data->opts.checkout_strategy &
                (GIT_CHECKOUT_CONFLICT_STYLE_MERGE | GIT_CHECKOUT_CONFLICT_STYLE_DIFF3)) == 0) {
                git_config_entry *conflict_style = NULL;
                git_config *cfg = NULL;

                if ((error = git_repository_config__weakptr(&cfg, repo)) < 0 ||
                        (error = git_config_get_entry(&conflict_style, cfg, "merge.conflictstyle")) < 0 ||
                        error == GIT_ENOTFOUND)
                        ;
                else if (error)
                        goto cleanup;
                else if (strcmp(conflict_style->value, "merge") == 0)
                        data->opts.checkout_strategy |= GIT_CHECKOUT_CONFLICT_STYLE_MERGE;
                else if (strcmp(conflict_style->value, "diff3") == 0)
                        data->opts.checkout_strategy |= GIT_CHECKOUT_CONFLICT_STYLE_DIFF3;
                else {
                        giterr_set(GITERR_CHECKOUT, "unknown style '%s' given for 'merge.conflictstyle'",
                                conflict_style->value);
                        error = -1;
                        git_config_entry_free(conflict_style);
                        goto cleanup;
                }
                git_config_entry_free(conflict_style);
        }

        git_pool_init(&data->pool, 1);

        if ((error = git_vector_init(&data->removes, 0, git__strcmp_cb)) < 0 ||
                (error = git_vector_init(&data->remove_conflicts, 0, NULL)) < 0 ||
                (error = git_vector_init(&data->update_conflicts, 0, NULL)) < 0 ||
                (error = git_buf_puts(&data->target_path, data->opts.target_directory)) < 0 ||
                (error = git_path_to_dir(&data->target_path)) < 0 ||
                (error = git_strmap_alloc(&data->mkdir_map)) < 0)
                goto cleanup;

        data->target_len = git_buf_len(&data->target_path);

        git_attr_session__init(&data->attr_session, data->repo);

cleanup:
        if (error < 0)
                checkout_data_clear(data);

        return error;
}

#define CHECKOUT_INDEX_DONT_WRITE_MASK \
        (GIT_CHECKOUT_DONT_UPDATE_INDEX | GIT_CHECKOUT_DONT_WRITE_INDEX)

int git_checkout_iterator(
        git_iterator *target,
        git_index *index,
        const git_checkout_options *opts)
{
        int error = 0;
        git_iterator *baseline = NULL, *workdir = NULL;
        git_iterator_options baseline_opts = GIT_ITERATOR_OPTIONS_INIT,
                workdir_opts = GIT_ITERATOR_OPTIONS_INIT;
        checkout_data data = {0};
        git_diff_options diff_opts = GIT_DIFF_OPTIONS_INIT;
        uint32_t *actions = NULL;
        size_t *counts = NULL;

        /* initialize structures and options */
        error = checkout_data_init(&data, target, opts);
        if (error < 0)
                return error;

        diff_opts.flags =
                GIT_DIFF_INCLUDE_UNMODIFIED |
                GIT_DIFF_INCLUDE_UNREADABLE |
                GIT_DIFF_INCLUDE_UNTRACKED |
                GIT_DIFF_RECURSE_UNTRACKED_DIRS | /* needed to match baseline */
                GIT_DIFF_INCLUDE_IGNORED |
                GIT_DIFF_INCLUDE_TYPECHANGE |
                GIT_DIFF_INCLUDE_TYPECHANGE_TREES |
                GIT_DIFF_SKIP_BINARY_CHECK |
                GIT_DIFF_INCLUDE_CASECHANGE;
        if (data.opts.checkout_strategy & GIT_CHECKOUT_DISABLE_PATHSPEC_MATCH)
                diff_opts.flags |= GIT_DIFF_DISABLE_PATHSPEC_MATCH;
        if (data.opts.paths.count > 0)
                diff_opts.pathspec = data.opts.paths;

        /* set up iterators */

        workdir_opts.flags = git_iterator_ignore_case(target) ?
                GIT_ITERATOR_IGNORE_CASE : GIT_ITERATOR_DONT_IGNORE_CASE;
        workdir_opts.flags |= GIT_ITERATOR_DONT_AUTOEXPAND;
        workdir_opts.start = data.pfx;
        workdir_opts.end = data.pfx;

        if ((error = git_iterator_reset_range(target, data.pfx, data.pfx)) < 0 ||
                (error = git_iterator_for_workdir_ext(
                        &workdir, data.repo, data.opts.target_directory, index, NULL,
                        &workdir_opts)) < 0)
                goto cleanup;

        baseline_opts.flags = git_iterator_ignore_case(target) ?
                GIT_ITERATOR_IGNORE_CASE : GIT_ITERATOR_DONT_IGNORE_CASE;
        baseline_opts.start = data.pfx;
        baseline_opts.end = data.pfx;
        if (opts && (opts->checkout_strategy & GIT_CHECKOUT_DISABLE_PATHSPEC_MATCH)) {
                baseline_opts.pathlist.count = opts->paths.count;
                baseline_opts.pathlist.strings = opts->paths.strings;
        }

        if (data.opts.baseline_index) {
                if ((error = git_iterator_for_index(
                                &baseline, git_index_owner(data.opts.baseline_index),
                                data.opts.baseline_index, &baseline_opts)) < 0)
                        goto cleanup;
        } else {
                if ((error = git_iterator_for_tree(
                                &baseline, data.opts.baseline, &baseline_opts)) < 0)
                        goto cleanup;
        }

        /* Should not have case insensitivity mismatch */
        assert(git_iterator_ignore_case(workdir) == git_iterator_ignore_case(baseline));

        /* Generate baseline-to-target diff which will include an entry for
         * every possible update that might need to be made.
         */
        if ((error = git_diff__from_iterators(
                        &data.diff, data.repo, baseline, target, &diff_opts)) < 0)
                goto cleanup;

        /* Loop through diff (and working directory iterator) building a list of
         * actions to be taken, plus look for conflicts and send notifications,
         * then loop through conflicts.
         */
        if ((error = checkout_get_actions(&actions, &counts, &data, workdir)) != 0)
                goto cleanup;

        data.total_steps = counts[CHECKOUT_ACTION__REMOVE] +
                counts[CHECKOUT_ACTION__REMOVE_CONFLICT] +
                counts[CHECKOUT_ACTION__UPDATE_BLOB] +
                counts[CHECKOUT_ACTION__UPDATE_SUBMODULE] +
                counts[CHECKOUT_ACTION__UPDATE_CONFLICT];

        report_progress(&data, NULL); /* establish 0 baseline */

        /* To deal with some order dependencies, perform remaining checkout
         * in three passes: removes, then update blobs, then update submodules.
         */
        if (counts[CHECKOUT_ACTION__REMOVE] > 0 &&
                (error = checkout_remove_the_old(actions, &data)) < 0)
                goto cleanup;

        if (counts[CHECKOUT_ACTION__REMOVE_CONFLICT] > 0 &&
                (error = checkout_remove_conflicts(&data)) < 0)
                goto cleanup;

        if (counts[CHECKOUT_ACTION__UPDATE_BLOB] > 0 &&
                (error = checkout_create_the_new(actions, &data)) < 0)
                goto cleanup;

        if (counts[CHECKOUT_ACTION__UPDATE_SUBMODULE] > 0 &&
                (error = checkout_create_submodules(actions, &data)) < 0)
                goto cleanup;

        if (counts[CHECKOUT_ACTION__UPDATE_CONFLICT] > 0 &&
                (error = checkout_create_conflicts(&data)) < 0)
                goto cleanup;

        if (data.index != git_iterator_index(target) &&
                (error = checkout_extensions_update_index(&data)) < 0)
                goto cleanup;

        assert(data.completed_steps == data.total_steps);

        if (data.opts.perfdata_cb)
                data.opts.perfdata_cb(&data.perfdata, data.opts.perfdata_payload);

cleanup:
        if (!error && data.index != NULL &&
                (data.strategy & CHECKOUT_INDEX_DONT_WRITE_MASK) == 0)
                error = git_index_write(data.index);

        git_diff_free(data.diff);
        git_iterator_free(workdir);
        git_iterator_free(baseline);
        git__free(actions);
        git__free(counts);
        checkout_data_clear(&data);

        return error;
}

int git_checkout_index(
        git_repository *repo,
        git_index *index,
        const git_checkout_options *opts)
{
        int error, owned = 0;
        git_iterator *index_i;

        if (!index && !repo) {
                giterr_set(GITERR_CHECKOUT,
                        "must provide either repository or index to checkout");
                return -1;
        }

        if (index && repo &&
                git_index_owner(index) &&
                git_index_owner(index) != repo) {
                giterr_set(GITERR_CHECKOUT,
                        "index to checkout does not match repository");
                return -1;
        } else if(index && repo && !git_index_owner(index)) {
                GIT_REFCOUNT_OWN(index, repo);
                owned = 1;
        }

        if (!repo)
                repo = git_index_owner(index);

        if (!index && (error = git_repository_index__weakptr(&index, repo)) < 0)
                return error;
        GIT_REFCOUNT_INC(index);

        if (!(error = git_iterator_for_index(&index_i, repo, index, NULL)))
                error = git_checkout_iterator(index_i, index, opts);

        if (owned)
                GIT_REFCOUNT_OWN(index, NULL);

        git_iterator_free(index_i);
        git_index_free(index);

        return error;
}

int git_checkout_tree(
        git_repository *repo,
        const git_object *treeish,
        const git_checkout_options *opts)
{
        int error;
        git_index *index;
        git_tree *tree = NULL;
        git_iterator *tree_i = NULL;
        git_iterator_options iter_opts = GIT_ITERATOR_OPTIONS_INIT;

        if (!treeish && !repo) {
                giterr_set(GITERR_CHECKOUT,
                        "must provide either repository or tree to checkout");
                return -1;
        }
        if (treeish && repo && git_object_owner(treeish) != repo) {
                giterr_set(GITERR_CHECKOUT,
                        "object to checkout does not match repository");
                return -1;
        }

        if (!repo)
                repo = git_object_owner(treeish);

        if (treeish) {
                if (git_object_peel((git_object **)&tree, treeish, GIT_OBJ_TREE) < 0) {
                        giterr_set(
                                GITERR_CHECKOUT, "provided object cannot be peeled to a tree");
                        return -1;
                }
        }
        else {
                if ((error = checkout_lookup_head_tree(&tree, repo)) < 0) {
                        if (error != GIT_EUNBORNBRANCH)
                                giterr_set(
                                        GITERR_CHECKOUT,
                                        "HEAD could not be peeled to a tree and no treeish given");
                        return error;
                }
        }

        if ((error = git_repository_index(&index, repo)) < 0)
                return error;

        if (opts && (opts->checkout_strategy & GIT_CHECKOUT_DISABLE_PATHSPEC_MATCH)) {
                iter_opts.pathlist.count = opts->paths.count;
                iter_opts.pathlist.strings = opts->paths.strings;
        }

        if (!(error = git_iterator_for_tree(&tree_i, tree, &iter_opts)))
                error = git_checkout_iterator(tree_i, index, opts);

        git_iterator_free(tree_i);
        git_index_free(index);
        git_tree_free(tree);

        return error;
}

int git_checkout_head(
        git_repository *repo,
        const git_checkout_options *opts)
{
        assert(repo);
        return git_checkout_tree(repo, NULL, opts);
}

int git_checkout_init_options(git_checkout_options *opts, unsigned int version)
{
        GIT_INIT_STRUCTURE_FROM_TEMPLATE(
                opts, version, git_checkout_options, GIT_CHECKOUT_OPTIONS_INIT);
        return 0;
}