[libgit2.git] / src / refs.c

/*
 * Copyright (C) 2009-2011 the libgit2 contributors
 *
 * 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 "refs.h"
#include "hash.h"
#include "repository.h"
#include "fileops.h"
#include "pack.h"

#include <git2/tag.h>
#include <git2/object.h>

#define MAX_NESTING_LEVEL 5

typedef struct {
	git_repository *owner;
	char *name;
	unsigned int type;
	time_t mtime;
} reference;

typedef struct {
	reference ref;
	git_oid oid;
	git_oid peel_target;
} reference_oid;

typedef struct {
	reference ref;
	char *target;
} reference_symbolic;

static const int default_table_size = 32;

static uint32_t reftable_hash(const void *key, int hash_id)
{
	static uint32_t hash_seeds[GIT_HASHTABLE_HASHES] = {
		2147483647,
		0x5d20bb23,
		0x7daaab3c
	};

	return git__hash(key, strlen((const char *)key), hash_seeds[hash_id]);
}

static void reference_free(reference *reference);
static int reference_create(reference **ref_out, git_repository *repo, const char *name, git_rtype type);
static int reference_read(git_fbuffer *file_content, time_t *mtime, const char *repo_path, const char *ref_name, int *updated);

static int reference_set_target(reference *ref, const char *target);
static int reference_set_oid(reference *ref, const git_oid *oid);

static int reference_delete(reference *ref);

/* loose refs */
static int loose_parse_symbolic(reference *ref, git_fbuffer *file_content);
static int loose_parse_oid(reference *ref, git_fbuffer *file_content);
static int loose_lookup(reference **ref_out, git_repository *repo, const char *name, int skip_symbolic);
static int loose_write(reference *ref);
static int loose_update(reference *ref);

/* packed refs */
static int packed_parse_peel(reference_oid *tag_ref, const char **buffer_out, const char *buffer_end);
static int packed_parse_oid(reference_oid **ref_out, git_repository *repo, const char **buffer_out, const char *buffer_end);
static int packed_load(git_repository *repo);
static int packed_loadloose(git_repository *repository);
static int packed_write_ref(reference_oid *ref, git_filebuf *file);
static int packed_find_peel(reference_oid *ref);
static int packed_remove_loose(git_repository *repo, git_vector *packing_list);
static int packed_sort(const void *a, const void *b);
static int packed_write(git_repository *repo);

/* internal helpers */
static int reference_available(git_repository *repo, const char *ref, const char *old_ref);
static int reference_lookup(reference **out, git_repository *repo, const char *name);

/* name normalization */
static int check_valid_ref_char(char ch);
static int normalize_name(char *buffer_out, size_t out_size, const char *name, int is_oid_ref);

/* reference transition */
static git_reference * reference_create_external(reference *ref);
static reference * reference_get_internal(git_reference *ref);


static void reference_free(reference *reference)
{
	if (reference == NULL)
		return;

	if (reference->name)
		git__free(reference->name);

	if (reference->type == GIT_REF_SYMBOLIC)
		git__free(((reference_symbolic *)reference)->target);

	git__free(reference);
}

static int reference_create(
	reference **ref_out,
	git_repository *repo,
	const char *name,
	git_rtype type)
{
	char normalized[GIT_REFNAME_MAX];
	int error = GIT_SUCCESS, size;
	reference *reference = NULL;

	assert(ref_out && repo && name);

	if (type == GIT_REF_SYMBOLIC)
		size = sizeof(reference_symbolic);
	else if (type == GIT_REF_OID)
		size = sizeof(reference_oid);
	else
		return git__throw(GIT_EINVALIDARGS,
			"Invalid reference type. Use either GIT_REF_OID or GIT_REF_SYMBOLIC as type specifier");

	reference = git__malloc(size);
	if (reference == NULL)
		return GIT_ENOMEM;

	memset(reference, 0x0, size);
	reference->owner = repo;
	reference->type = type;

	error = normalize_name(normalized, sizeof(normalized), name, (type & GIT_REF_OID));
	if (error < GIT_SUCCESS)
		goto cleanup;

	reference->name = git__strdup(normalized);
	if (reference->name == NULL) {
		error = GIT_ENOMEM;
		goto cleanup;
	}

	*ref_out = reference;

	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to create reference");

cleanup:
	reference_free(reference);
	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to create reference");
}

static int reference_read(git_fbuffer *file_content, time_t *mtime, const char *repo_path, const char *ref_name, int *updated)
{
	char path[GIT_PATH_MAX];

	assert(file_content && repo_path && ref_name);

	/* Determine the full path of the file */
	git_path_join(path, repo_path, ref_name);

	return git_futils_readbuffer_updated(file_content, path, mtime, updated);
}

static git_reference * reference_create_external(reference *ref)
{
	size_t size = sizeof(git_reference);
	git_reference *out;

	out = git__malloc(size);
	if (out == NULL)
		return NULL;

	memset(out, 0x0, size);

	out->owner = ref->owner;

	out->name = git__strdup(ref->name);
	if (out->name == NULL) {
		git__free(out);
		return NULL;
	}

	return out;
}

static reference * reference_get_internal(git_reference *ref)
{
	reference *out = NULL;

	reference_lookup(&out, ref->owner, ref->name);

	return out;
}

static int loose_update(reference *ref)
{
	int error, updated;
	git_fbuffer ref_file = GIT_FBUFFER_INIT;

	if (ref->type & GIT_REF_PACKED)
		return packed_load(ref->owner);


/*	error = reference_read(NULL, &ref_time, ref->owner->path_repository, ref->name);
	if (error < GIT_SUCCESS)
		goto cleanup;

	if (ref_time == ref->mtime)
		return GIT_SUCCESS;
*/
	error = reference_read(&ref_file, &ref->mtime, ref->owner->path_repository, ref->name, &updated);
	if (error < GIT_SUCCESS)
		goto cleanup;

	if (!updated)
		goto cleanup;

	if (ref->type == GIT_REF_SYMBOLIC)
		error = loose_parse_symbolic(ref, &ref_file);
	else if (ref->type == GIT_REF_OID)
		error = loose_parse_oid(ref, &ref_file);
	else
		error = git__throw(GIT_EOBJCORRUPTED,
			"Invalid reference type (%d) for loose reference", ref->type);

cleanup:
	git_futils_freebuffer(&ref_file);
	if (error != GIT_SUCCESS) {
		reference_free(ref);
		git_hashtable_remove(ref->owner->references.loose_cache, ref->name);
	}

	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to update loose reference");
}

static int loose_parse_symbolic(reference *ref, git_fbuffer *file_content)
{
	const unsigned int header_len = strlen(GIT_SYMREF);
	const char *refname_start;
	char *eol;
	reference_symbolic *ref_sym;

	refname_start = (const char *)file_content->data;
	ref_sym = (reference_symbolic *)ref;

	if (file_content->len < (header_len + 1))
		return git__throw(GIT_EOBJCORRUPTED,
			"Failed to parse loose reference. Object too short");

	/*
	 * Assume we have already checked for the header
	 * before calling this function
	 */

	refname_start += header_len;

	git__free(ref_sym->target);
	ref_sym->target = git__strdup(refname_start);
	if (ref_sym->target == NULL)
		return GIT_ENOMEM;

	/* remove newline at the end of file */
	eol = strchr(ref_sym->target, '\n');
	if (eol == NULL)
		return git__throw(GIT_EOBJCORRUPTED,
			"Failed to parse loose reference. Missing EOL");

	*eol = '\0';
	if (eol[-1] == '\r')
		eol[-1] = '\0';

	return GIT_SUCCESS;
}

static int loose_parse_oid(reference *ref, git_fbuffer *file_content)
{
	int error;
	reference_oid *ref_oid;
	char *buffer;

	buffer = (char *)file_content->data;
	ref_oid = (reference_oid *)ref;

	/* File format: 40 chars (OID) + newline */
	if (file_content->len < GIT_OID_HEXSZ + 1)
		return git__throw(GIT_EOBJCORRUPTED,
			"Failed to parse loose reference. Reference too short");

	if ((error = git_oid_fromstr(&ref_oid->oid, buffer)) < GIT_SUCCESS)
		return git__rethrow(GIT_EOBJCORRUPTED, "Failed to parse loose reference.");

	buffer = buffer + GIT_OID_HEXSZ;
	if (*buffer == '\r')
		buffer++;

	if (*buffer != '\n')
		return git__throw(GIT_EOBJCORRUPTED,
			"Failed to parse loose reference. Missing EOL");

	return GIT_SUCCESS;
}


static git_rtype loose_guess_rtype(const char *full_path)
{
	git_fbuffer ref_file = GIT_FBUFFER_INIT;
	git_rtype type;

	type = GIT_REF_INVALID;

	if (git_futils_readbuffer(&ref_file, full_path) == GIT_SUCCESS) {
		if (git__prefixcmp((const char *)(ref_file.data), GIT_SYMREF) == 0)
			type = GIT_REF_SYMBOLIC;
		else
			type = GIT_REF_OID;
	}

	git_futils_freebuffer(&ref_file);
	return type;
}

static int loose_lookup(
		reference **ref_out,
		git_repository *repo,
		const char *name,
		int skip_symbolic)
{
	int error = GIT_SUCCESS;
	git_fbuffer ref_file = GIT_FBUFFER_INIT;
	reference *ref = NULL;
	time_t ref_time = 0;

	*ref_out = NULL;

	error = reference_read(&ref_file, &ref_time, repo->path_repository, name, NULL);
	if (error < GIT_SUCCESS)
		goto cleanup;

	if (git__prefixcmp((const char *)(ref_file.data), GIT_SYMREF) == 0) {
		if (skip_symbolic)
			return GIT_SUCCESS;

		error = reference_create(&ref, repo, name, GIT_REF_SYMBOLIC);
		if (error < GIT_SUCCESS)
			goto cleanup;

		error = loose_parse_symbolic(ref, &ref_file);
	} else {
		error = reference_create(&ref, repo, name, GIT_REF_OID);
		if (error < GIT_SUCCESS)
			goto cleanup;

		error = loose_parse_oid(ref, &ref_file);
	}

	if (error < GIT_SUCCESS)
		goto cleanup;

	ref->mtime = ref_time;
	*ref_out = ref;
	git_futils_freebuffer(&ref_file);
	return GIT_SUCCESS;

cleanup:
	git_futils_freebuffer(&ref_file);
	reference_free(ref);
	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to lookup loose reference");
}

static int loose_write(reference *ref)
{
	git_filebuf file;
	char ref_path[GIT_PATH_MAX];
	int error;
	struct stat st;

	git_path_join(ref_path, ref->owner->path_repository, ref->name);

	if ((error = git_filebuf_open(&file, ref_path, GIT_FILEBUF_FORCE)) < GIT_SUCCESS)
		return git__rethrow(error, "Failed to write loose reference");

	if (ref->type & GIT_REF_OID) {
		reference_oid *ref_oid = (reference_oid *)ref;
		char oid[GIT_OID_HEXSZ + 1];

		memset(oid, 0x0, sizeof(oid));

		git_oid_fmt(oid, &ref_oid->oid);
		error = git_filebuf_printf(&file, "%s\n", oid);
		if (error < GIT_SUCCESS)
			goto unlock;

	} else if (ref->type & GIT_REF_SYMBOLIC) { /* GIT_REF_SYMBOLIC */
		reference_symbolic *ref_sym = (reference_symbolic *)ref;

		error = git_filebuf_printf(&file, GIT_SYMREF "%s\n", ref_sym->target);
	} else {
		error = git__throw(GIT_EOBJCORRUPTED, "Failed to write reference. Invalid reference type");
		goto unlock;
	}

	error = git_filebuf_commit(&file, GIT_REFS_FILE_MODE);

	if (p_stat(ref_path, &st) == GIT_SUCCESS)
		ref->mtime = st.st_mtime;

	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to write loose reference");

unlock:
	git_filebuf_cleanup(&file);
	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to write loose reference");
}

static int packed_parse_peel(
		reference_oid *tag_ref,
		const char **buffer_out,
		const char *buffer_end)
{
	const char *buffer = *buffer_out + 1;

	assert(buffer[-1] == '^');

	/* Ensure it's not the first entry of the file */
	if (tag_ref == NULL)
		return git__throw(GIT_EPACKEDREFSCORRUPTED, "Failed to parse packed reference. Reference is the first entry of the file");

	/* Ensure reference is a tag */
	if (git__prefixcmp(tag_ref->ref.name, GIT_REFS_TAGS_DIR) != 0)
		return git__throw(GIT_EPACKEDREFSCORRUPTED, "Failed to parse packed reference. Reference is not a tag");

	if (buffer + GIT_OID_HEXSZ >= buffer_end)
		return git__throw(GIT_EPACKEDREFSCORRUPTED, "Failed to parse packed reference. Buffer too small");

	/* Is this a valid object id? */
	if (git_oid_fromstr(&tag_ref->peel_target, buffer) < GIT_SUCCESS)
		return git__throw(GIT_EPACKEDREFSCORRUPTED, "Failed to parse packed reference. Not a valid object ID");

	buffer = buffer + GIT_OID_HEXSZ;
	if (*buffer == '\r')
		buffer++;

	if (*buffer != '\n')
		return git__throw(GIT_EPACKEDREFSCORRUPTED, "Failed to parse packed reference. Buffer not terminated correctly");

	*buffer_out = buffer + 1;
	tag_ref->ref.type |= GIT_REF_HAS_PEEL;

	return GIT_SUCCESS;
}

static int packed_parse_oid(
		reference_oid **ref_out,
		git_repository *repo,
		const char **buffer_out,
		const char *buffer_end)
{
	git_reference *_ref = NULL;
	reference_oid *ref = NULL;

	const char *buffer = *buffer_out;
	const char *refname_begin, *refname_end;

	int error = GIT_SUCCESS;
	int refname_len;
	char refname[GIT_REFNAME_MAX];
	git_oid id;

	refname_begin = (buffer + GIT_OID_HEXSZ + 1);
	if (refname_begin >= buffer_end ||
		refname_begin[-1] != ' ') {
		error = GIT_EPACKEDREFSCORRUPTED;
		goto cleanup;
	}

	/* Is this a valid object id? */
	if ((error = git_oid_fromstr(&id, buffer)) < GIT_SUCCESS)
		goto cleanup;

	refname_end = memchr(refname_begin, '\n', buffer_end - refname_begin);
	if (refname_end == NULL) {
		error = GIT_EPACKEDREFSCORRUPTED;
		goto cleanup;
	}

	refname_len = refname_end - refname_begin;

	memcpy(refname, refname_begin, refname_len);
	refname[refname_len] = 0;

	if (refname[refname_len - 1] == '\r')
		refname[refname_len - 1] = 0;

	error = reference_create((reference **)&_ref, repo, refname, GIT_REF_OID);
	if (error < GIT_SUCCESS)
		goto cleanup;

	ref = (reference_oid *)_ref;

	git_oid_cpy(&ref->oid, &id);
	ref->ref.type |= GIT_REF_PACKED;

	*ref_out = ref;
	*buffer_out = refname_end + 1;

	return GIT_SUCCESS;

cleanup:
	reference_free((reference *)ref);
	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to parse OID of packed reference");
}

static int packed_load(git_repository *repo)
{
	int error = GIT_SUCCESS, updated;
	git_fbuffer packfile = GIT_FBUFFER_INIT;
	const char *buffer_start, *buffer_end;
	git_refcache *ref_cache = &repo->references;

	/* First we make sure we have allocated the hash table */
	if (ref_cache->packfile == NULL) {
		ref_cache->packfile = git_hashtable_alloc(
			default_table_size,
			reftable_hash,
			(git_hash_keyeq_ptr)(&git__strcmp_cb));

		if (ref_cache->packfile == NULL) {
			error = GIT_ENOMEM;
			goto cleanup;
		}
	}

	error = reference_read(&packfile, &ref_cache->packfile_time,
							repo->path_repository, GIT_PACKEDREFS_FILE, &updated);

	/*
	 * If we couldn't find the file, we need to clear the table and
	 * return. On any other error, we return that error. If everything
	 * went fine and the file wasn't updated, then there's nothing new
	 * for us here, so just return. Anything else means we need to
	 * refresh the packed refs.
	 */
	if (error == GIT_ENOTFOUND) {
		git_hashtable_clear(ref_cache->packfile);
		return GIT_SUCCESS;
	} else if (error < GIT_SUCCESS) {
		return git__rethrow(error, "Failed to read packed refs");
	} else if (!updated) {
		return GIT_SUCCESS;
	}

	/*
	 * At this point, we want to refresh the packed refs. We already
	 * have the contents in our buffer.
	 */

	git_hashtable_clear(ref_cache->packfile);

	buffer_start = (const char *)packfile.data;
	buffer_end = (const char *)(buffer_start) + packfile.len;

	while (buffer_start < buffer_end && buffer_start[0] == '#') {
		buffer_start = strchr(buffer_start, '\n');
		if (buffer_start == NULL) {
			error = GIT_EPACKEDREFSCORRUPTED;
			goto cleanup;
		}
		buffer_start++;
	}

	while (buffer_start < buffer_end) {
		reference_oid *ref = NULL;

		error = packed_parse_oid(&ref, repo, &buffer_start, buffer_end);
		if (error < GIT_SUCCESS)
			goto cleanup;

		if (buffer_start[0] == '^') {
			error = packed_parse_peel(ref, &buffer_start, buffer_end);
			if (error < GIT_SUCCESS)
				goto cleanup;
		}

		error = git_hashtable_insert(ref_cache->packfile, ref->ref.name, ref);
		if (error < GIT_SUCCESS) {
			reference_free((reference *)ref);
			goto cleanup;
		}
	}

	git_futils_freebuffer(&packfile);
	return GIT_SUCCESS;

cleanup:
	git_hashtable_free(ref_cache->packfile);
	ref_cache->packfile = NULL;
	git_futils_freebuffer(&packfile);
	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to load packed references");
}


struct dirent_list_data {
	git_repository *repo;
	size_t repo_path_len;
	unsigned int list_flags;

	int (*callback)(const char *, void *);
	void *callback_payload;
};

static int _dirent_loose_listall(void *_data, char *full_path)
{
	struct dirent_list_data *data = (struct dirent_list_data *)_data;
	char *file_path = full_path + data->repo_path_len;

	if (git_futils_isdir(full_path) == GIT_SUCCESS)
		return git_futils_direach(full_path, GIT_PATH_MAX, _dirent_loose_listall, _data);

	/* do not add twice a reference that exists already in the packfile */
	if ((data->list_flags & GIT_REF_PACKED) != 0 &&
		git_hashtable_lookup(data->repo->references.packfile, file_path) != NULL)
		return GIT_SUCCESS;

	if (data->list_flags != GIT_REF_LISTALL) {
		if ((data->list_flags & loose_guess_rtype(full_path)) == 0)
			return GIT_SUCCESS; /* we are filtering out this reference */
	}

	return data->callback(file_path, data->callback_payload);
}

static int _dirent_loose_load(void *data, char *full_path)
{
	git_repository *repository = (git_repository *)data;
	void *old_ref = NULL;
	reference *ref;
	char *file_path;
	int error;

	if (git_futils_isdir(full_path) == GIT_SUCCESS)
		return git_futils_direach(full_path, GIT_PATH_MAX, _dirent_loose_load, repository);

	file_path = full_path + strlen(repository->path_repository);
	error = loose_lookup(&ref, repository, file_path, 1);
	if (error == GIT_SUCCESS && ref != NULL) {
		ref->type |= GIT_REF_PACKED;

		if (git_hashtable_insert2(repository->references.packfile, ref->name, ref, &old_ref) < GIT_SUCCESS) {
			reference_free(ref);
			return GIT_ENOMEM;
		}

		if (old_ref != NULL)
			reference_free((reference *)old_ref);
	}

	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to load loose dirent");
}

/*
 * Load all the loose references from the repository
 * into the in-memory Packfile, and build a vector with
 * all the references so it can be written back to
 * disk.
 */
static int packed_loadloose(git_repository *repository)
{
	char refs_path[GIT_PATH_MAX];

	/* the packfile must have been previously loaded! */
	assert(repository->references.packfile);

	git_path_join(refs_path, repository->path_repository, GIT_REFS_DIR);

	/* Remove any loose references from the cache */
	{
		const void *GIT_UNUSED(_unused);
		reference *reference;

		GIT_HASHTABLE_FOREACH(repository->references.loose_cache, _unused, reference,
			reference_free(reference);
		);
	}

	git_hashtable_clear(repository->references.loose_cache);

	/*
	 * Load all the loose files from disk into the Packfile table.
	 * This will overwrite any old packed entries with their
	 * updated loose versions
	 */
	return git_futils_direach(refs_path, GIT_PATH_MAX, _dirent_loose_load, repository);
}

/*
 * Write a single reference into a packfile
 */
static int packed_write_ref(reference_oid *ref, git_filebuf *file)
{
	int error;
	char oid[GIT_OID_HEXSZ + 1];

	git_oid_fmt(oid, &ref->oid);
	oid[GIT_OID_HEXSZ] = 0;

	/*
	 * For references that peel to an object in the repo, we must
	 * write the resulting peel on a separate line, e.g.
	 *
	 *	6fa8a902cc1d18527e1355773c86721945475d37 refs/tags/libgit2-0.4
	 *	^2ec0cb7959b0bf965d54f95453f5b4b34e8d3100
	 *
	 * This obviously only applies to tags.
	 * The required peels have already been loaded into `ref->peel_target`.
	 */
	if (ref->ref.type & GIT_REF_HAS_PEEL) {
		char peel[GIT_OID_HEXSZ + 1];
		git_oid_fmt(peel, &ref->peel_target);
		peel[GIT_OID_HEXSZ] = 0;

		error = git_filebuf_printf(file, "%s %s\n^%s\n", oid, ref->ref.name, peel);
	} else {
		error = git_filebuf_printf(file, "%s %s\n", oid, ref->ref.name);
	}

	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to write packed reference");
}

/*
 * Find out what object this reference resolves to.
 *
 * For references that point to a 'big' tag (e.g. an
 * actual tag object on the repository), we need to
 * cache on the packfile the OID of the object to
 * which that 'big tag' is pointing to.
 */
static int packed_find_peel(reference_oid *ref)
{
	git_object *object;
	int error;

	if (ref->ref.type & GIT_REF_HAS_PEEL)
		return GIT_SUCCESS;

	/*
	 * Only applies to tags, i.e. references
	 * in the /refs/tags folder
	 */
	if (git__prefixcmp(ref->ref.name, GIT_REFS_TAGS_DIR) != 0)
		return GIT_SUCCESS;

	/*
	 * Find the tagged object in the repository
	 */
	error = git_object_lookup(&object, ref->ref.owner, &ref->oid, GIT_OBJ_ANY);
	if (error < GIT_SUCCESS)
		return git__throw(GIT_EOBJCORRUPTED, "Failed to find packed reference");

	/*
	 * If the tagged object is a Tag object, we need to resolve it;
	 * if the ref is actually a 'weak' ref, we don't need to resolve
	 * anything.
	 */
	if (git_object_type(object) == GIT_OBJ_TAG) {
		git_tag *tag = (git_tag *)object;

		/*
		 * Find the object pointed at by this tag
		 */
		git_oid_cpy(&ref->peel_target, git_tag_target_oid(tag));
		ref->ref.type |= GIT_REF_HAS_PEEL;

		/*
		 * The reference has now cached the resolved OID, and is
		 * marked at such. When written to the packfile, it'll be
		 * accompanied by this resolved oid
		 */
	}

	git_object_close(object);

	return GIT_SUCCESS;
}

/*
 * Remove all loose references
 *
 * Once we have successfully written a packfile,
 * all the loose references that were packed must be
 * removed from disk.
 *
 * This is a dangerous method; make sure the packfile
 * is well-written, because we are destructing references
 * here otherwise.
 */
static int packed_remove_loose(git_repository *repo, git_vector *packing_list)
{
	unsigned int i;
	char full_path[GIT_PATH_MAX];
	int error = GIT_SUCCESS;
	reference *r;

	for (i = 0; i < packing_list->length; ++i) {
		reference *ref = git_vector_get(packing_list, i);

		/* Ensure the packed reference doesn't exist
		 * in a (more up-to-date?) state as a loose reference
		 */
		r = git_hashtable_lookup(ref->owner->references.loose_cache, ref->name);
		if (r != NULL)
			continue;

		git_path_join(full_path, repo->path_repository, ref->name);

		if (git_futils_exists(full_path) == GIT_SUCCESS &&
			p_unlink(full_path) < GIT_SUCCESS)
			error = GIT_EOSERR;

		/*
		 * if we fail to remove a single file, this is *not* good,
		 * but we should keep going and remove as many as possible.
		 * After we've removed as many files as possible, we return
		 * the error code anyway.
		 *
		 * TODO: mark this with a very special error code?
		 * GIT_EFAILTORMLOOSE
		 */
	}

	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to remove loose packed reference");
}

static int packed_sort(const void *a, const void *b)
{
	const reference *ref_a = (const reference *)a;
	const reference *ref_b = (const reference *)b;

	return strcmp(ref_a->name, ref_b->name);
}

/*
 * Write all the contents in the in-memory packfile to disk.
 */
static int packed_write(git_repository *repo)
{
	git_filebuf pack_file;
	int error;
	unsigned int i;
	char pack_file_path[GIT_PATH_MAX];

	git_vector packing_list;
	size_t total_refs;

	assert(repo && repo->references.packfile);

	total_refs = repo->references.packfile->key_count;
	if ((error = git_vector_init(&packing_list, total_refs, packed_sort)) < GIT_SUCCESS)
		return git__rethrow(error, "Failed to write packed reference");

	/* Load all the packfile into a vector */
	{
		reference *reference;
		const void *GIT_UNUSED(_unused);

		GIT_HASHTABLE_FOREACH(repo->references.packfile, _unused, reference,
			git_vector_insert(&packing_list, reference); /* cannot fail: vector already has the right size */
		);
	}

	/* sort the vector so the entries appear sorted on the packfile */
	git_vector_sort(&packing_list);

	/* Now we can open the file! */
	git_path_join(pack_file_path, repo->path_repository, GIT_PACKEDREFS_FILE);
	if ((error = git_filebuf_open(&pack_file, pack_file_path, 0)) < GIT_SUCCESS)
		return git__rethrow(error, "Failed to write packed reference");

	/* Packfiles have a header... apparently
	 * This is in fact not required, but we might as well print it
	 * just for kicks */
	if ((error = git_filebuf_printf(&pack_file, "%s\n", GIT_PACKEDREFS_HEADER)) < GIT_SUCCESS)
		return git__rethrow(error, "Failed to write packed reference");

	for (i = 0; i < packing_list.length; ++i) {
		reference_oid *ref = (reference_oid *)git_vector_get(&packing_list, i);

		/* only direct references go to the packfile; otherwise
		 * this is a disaster */
		assert(ref->ref.type & GIT_REF_OID);

		if ((error = packed_find_peel(ref)) < GIT_SUCCESS) {
			error = git__throw(GIT_EOBJCORRUPTED, "A reference cannot be peeled");
			goto cleanup;
		}


		if ((error = packed_write_ref(ref, &pack_file)) < GIT_SUCCESS)
			goto cleanup;
	}

cleanup:
	/* if we've written all the references properly, we can commit
	 * the packfile to make the changes effective */
	if (error == GIT_SUCCESS) {
		error = git_filebuf_commit(&pack_file, GIT_PACK_FILE_MODE);

		/* when and only when the packfile has been properly written,
		 * we can go ahead and remove the loose refs */
		if (error == GIT_SUCCESS) {
			struct stat st;

			error = packed_remove_loose(repo, &packing_list);

			if (p_stat(pack_file_path, &st) == GIT_SUCCESS)
				repo->references.packfile_time = st.st_mtime;
		}
	}
	else git_filebuf_cleanup(&pack_file);

	git_vector_free(&packing_list);

	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to write packed reference");
}

static int _reference_available_cb(const char *ref, void *data)
{
	const char *new, *old;
	git_vector *refs;

	assert(ref && data);

	refs = (git_vector *)data;

	new = (const char *)git_vector_get(refs, 0);
	old = (const char *)git_vector_get(refs, 1);

	if (!old || strcmp(old, ref)) {
		int reflen = strlen(ref);
		int newlen = strlen(new);
		int cmplen = reflen < newlen ? reflen : newlen;
		const char *lead = reflen < newlen ? new : ref;

		if (!strncmp(new, ref, cmplen) &&
			lead[cmplen] == '/')
			return GIT_EEXISTS;
	}

	return GIT_SUCCESS;
}

static int reference_available(git_repository *repo, const char *ref, const char* old_ref)
{
	int error;
	git_vector refs;

	if (git_vector_init(&refs, 2, NULL) < GIT_SUCCESS)
		return GIT_ENOMEM;

	git_vector_insert(&refs, (void *)ref);
	git_vector_insert(&refs, (void *)old_ref);

	error = git_reference_foreach(repo, GIT_REF_LISTALL, _reference_available_cb, (void *)&refs);

	git_vector_free(&refs);

	return error == GIT_SUCCESS ? GIT_SUCCESS : git__throw(GIT_EEXISTS, "Reference name `%s` conflicts with existing reference", ref);
}

int reference_lookup(reference **ref_out, git_repository *repo, const char *name)
{
	int error;
	char normalized_name[GIT_REFNAME_MAX];

	assert(ref_out && repo && name);

	*ref_out = NULL;

	error = normalize_name(normalized_name, sizeof(normalized_name), name, 0);
	if (error < GIT_SUCCESS)
		return git__rethrow(error, "Failed to lookup reference");

	/* First, check has been previously loaded and cached */
	*ref_out = git_hashtable_lookup(repo->references.loose_cache, normalized_name);
	if (*ref_out != NULL)
		return loose_update(*ref_out);

	/* Then check if there is a loose file for that reference.*/
	error = loose_lookup(ref_out, repo, normalized_name, 0);

	/* If the file exists, we store it on the cache */
	if (error == GIT_SUCCESS)
		return git_hashtable_insert(repo->references.loose_cache, (*ref_out)->name, (*ref_out));

	/* The loose lookup has failed, but not because the reference wasn't found;
	 * probably the loose reference is corrupted. this is bad. */
	if (error != GIT_ENOTFOUND)
		return git__rethrow(error, "Failed to lookup reference");

	/*
	 * If we cannot find a loose reference, we look into the packfile
	 * Load the packfile first if it hasn't been loaded
	 */
	/* load all the packed references */
	error = packed_load(repo);
	if (error < GIT_SUCCESS)
		return git__rethrow(error, "Failed to lookup reference");

	/* Look up on the packfile */
	*ref_out = git_hashtable_lookup(repo->references.packfile, normalized_name);
	if (*ref_out != NULL)
		return GIT_SUCCESS;

	/* The reference doesn't exist anywhere */
	return git__throw(GIT_ENOTFOUND, "Failed to lookup reference. Reference doesn't exist");
}

int git_reference_lookup(git_reference **ref_out, git_repository *repo, const char *name)
{
	int error;
	reference *ref;

	assert(ref_out && repo && name);

	*ref_out = NULL;

	error = reference_lookup(&ref, repo, name);
	if (error < GIT_SUCCESS)
		return error;

	*ref_out = reference_create_external(ref);
	if (*ref_out == NULL)
		return GIT_ENOMEM;

	return GIT_SUCCESS;
}

/**
 * Getters
 */
static git_rtype ref_type(reference *ref)
{
	assert(ref);

	if (ref->type & GIT_REF_OID)
		return GIT_REF_OID;

	if (ref->type & GIT_REF_SYMBOLIC)
		return GIT_REF_SYMBOLIC;

	return GIT_REF_INVALID;
}

git_rtype git_reference_type(git_reference *ref_in)
{
	reference *ref;

	assert(ref_in);

	ref = reference_get_internal(ref_in);
	if (ref == NULL)
		return GIT_REF_INVALID;

	return ref_type(ref);
}

int git_reference_is_packed(git_reference *ref_in)
{
	reference *ref;

	assert(ref_in);

	ref = reference_get_internal(ref_in);
	if (ref == NULL)
		return GIT_REF_INVALID;

	return !!(ref->type & GIT_REF_PACKED);
}

void git_reference_free(git_reference *ref)
{
	if (ref == NULL)
		return;

	if (ref->name)
		git__free(ref->name);

	git__free(ref);
}

const char *git_reference_name(git_reference *ref)
{
	assert(ref);
	return ref->name;
}

git_repository *git_reference_owner(git_reference *ref)
{
	assert(ref);
	return ref->owner;
}

static const git_oid *ref_oid(reference *ref)
{
	assert(ref);

	if ((ref->type & GIT_REF_OID) == 0)
		return NULL;

	if (loose_update(ref) < GIT_SUCCESS)
		return NULL;

	return &((reference_oid *)ref)->oid;
}

const git_oid *git_reference_oid(git_reference *ref_in)
{
	reference *ref;

	assert(ref_in);

	ref = reference_get_internal(ref_in);
	if (ref == NULL)
		return NULL;

	return ref_oid(ref);
}

static const char *ref_target(reference *ref)
{
	assert(ref);

	if ((ref->type & GIT_REF_SYMBOLIC) == 0)
		return NULL;

	if (loose_update(ref) < GIT_SUCCESS)
		return NULL;

	return ((reference_symbolic *)ref)->target;
}

const char *git_reference_target(git_reference *ref_in)
{
	reference *ref;

	assert(ref_in);

	ref = reference_get_internal(ref_in);
	if (ref == NULL)
		return NULL;

	return ref_target(ref);
}

static int reference_create_symbolic(reference **ref_out, git_repository *repo, const char *name, const char *target, int force)
{
	char normalized[GIT_REFNAME_MAX];
	int error = GIT_SUCCESS, updated = 0;
	reference *ref = NULL;
	void *old_ref = NULL;

	if (reference_lookup(&ref, repo, name) == GIT_SUCCESS && !force)
		return git__throw(GIT_EEXISTS, "Failed to create symbolic reference. Reference already exists");

	/*
	 * If they old ref was of the same type, then we can just update
	 * it (once we've checked that the target is valid). Otherwise we
	 * need a new reference because we can't make a symbolic ref out
	 * of an oid one.
	 * If if didn't exist, then we need to create a new one anyway.
		*/
	if (ref && ref->type & GIT_REF_SYMBOLIC){
		updated = 1;
	} else {
		ref = NULL;
		error = reference_create(&ref, repo, name, GIT_REF_SYMBOLIC);
		if (error < GIT_SUCCESS)
			goto cleanup;
	}

	/* The target can aither be the name of an object id reference or the name of another symbolic reference */
	error = normalize_name(normalized, sizeof(normalized), target, 0);
	if (error < GIT_SUCCESS)
		goto cleanup;

	/* set the target; this will write the reference on disk */
	error = reference_set_target(ref, normalized);
	if (error < GIT_SUCCESS)
		goto cleanup;

	/*
	 * If we didn't update the ref, then we need to insert or replace
	 * it in the loose cache. If we replaced a ref, free it.
	 */
	if (!updated){
		error = git_hashtable_insert2(repo->references.loose_cache, ref->name, ref, &old_ref);
		if (error < GIT_SUCCESS)
			goto cleanup;

		if (old_ref != NULL)
			reference_free((reference *)old_ref);
	}

	*ref_out = ref;

	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to create symbolic reference");

cleanup:
	reference_free(ref);
	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to create symbolic reference");
}

int git_reference_create_symbolic(git_reference **ref_out, git_repository *repo, const char *name, const char *target, int force)
{
	int error;
	reference *ref;

	error = reference_create_symbolic(&ref, repo, name, target, force);
	if (error < GIT_SUCCESS)
		return error;

	*ref_out = reference_create_external(ref);
	if (*ref_out == NULL)
		return GIT_ENOMEM;

	return GIT_SUCCESS;
}

static int reference_create_oid(reference **ref_out, git_repository *repo, const char *name, const git_oid *id, int force)
{
	int error = GIT_SUCCESS, updated = 0;
	reference *ref = NULL;
	void *old_ref = NULL;

	if(reference_lookup(&ref, repo, name) == GIT_SUCCESS && !force)
		return git__throw(GIT_EEXISTS, "Failed to create reference OID. Reference already exists");

	if ((error = reference_available(repo, name, NULL)) < GIT_SUCCESS)
		return git__rethrow(error, "Failed to create reference");

	/*
	 * If they old ref was of the same type, then we can just update
	 * it (once we've checked that the target is valid). Otherwise we
	 * need a new reference because we can't make a symbolic ref out
	 * of an oid one.
	 * If if didn't exist, then we need to create a new one anyway.
		*/
	if (ref && ref-> type & GIT_REF_OID){
		updated = 1;
	} else {
		ref = NULL;
		error = reference_create(&ref, repo, name, GIT_REF_OID);
		if (error < GIT_SUCCESS)
			goto cleanup;
	}

	/* set the oid; this will write the reference on disk */
	error = reference_set_oid(ref, id);
	if (error < GIT_SUCCESS)
		goto cleanup;

	if(!updated){
		error = git_hashtable_insert2(repo->references.loose_cache, ref->name, ref, &old_ref);
		if (error < GIT_SUCCESS)
			goto cleanup;

		if (old_ref != NULL)
			reference_free((reference *)old_ref);
	}

	*ref_out = ref;

	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to create reference OID");

cleanup:
	reference_free(ref);
	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to create reference OID");
}

int git_reference_create_oid(git_reference **ref_out, git_repository *repo, const char *name, const git_oid *id, int force)
{
	int error;
	reference *ref;

	error = reference_create_oid(&ref, repo, name, id, force);
	if (error < GIT_SUCCESS)
		return error;

	*ref_out = reference_create_external(ref);
	if (*ref_out == NULL)
		return GIT_ENOMEM;

	return GIT_SUCCESS;
}

/*
 * Change the OID target of a reference.
 *
 * For loose references, just change the oid in memory
 * and overwrite the file in disk.
 *
 * For packed files, this is not pretty:
 * For performance reasons, we write the new reference
 * loose on disk (it replaces the old on the packfile),
 * but we cannot invalidate the pointer to the reference,
 * and most importantly, the `packfile` object must stay
 * consistent with the representation of the packfile
 * on disk. This is what we need to:
 *
 * 1. Copy the reference
 * 2. Change the oid on the original
 * 3. Write the original to disk
 * 4. Write the original to the loose cache
 * 5. Replace the original with the copy (old reference) in the packfile cache
 */
int reference_set_oid(reference *ref, const git_oid *id)
{
	reference_oid *ref_oid;
	reference_oid *ref_old = NULL;
	int error = GIT_SUCCESS;

	if ((ref->type & GIT_REF_OID) == 0)
		return git__throw(GIT_EINVALIDREFSTATE, "Failed to set OID target of reference. Not an OID reference");

	ref_oid = (reference_oid *)ref;

	assert(ref->owner);

	/* Don't let the user create references to OIDs that
	 * don't exist in the ODB */
	if (!git_odb_exists(git_repository_database(ref->owner), id))
		return git__throw(GIT_ENOTFOUND, "Failed to set OID target of reference. OID doesn't exist in ODB");

	/* duplicate the reference;
	 * this copy will stay on the packfile cache */
	if (ref->type & GIT_REF_PACKED) {
		ref_old = git__malloc(sizeof(reference_oid));
		if (ref_old == NULL)
			return GIT_ENOMEM;

		ref_old->ref.name = git__strdup(ref->name);
		if (ref_old->ref.name == NULL) {
			git__free(ref_old);
			return GIT_ENOMEM;
		}
	}

	git_oid_cpy(&ref_oid->oid, id);
	ref->type &= ~GIT_REF_HAS_PEEL;

	error = loose_write(ref);
	if (error < GIT_SUCCESS)
		goto cleanup;

	if (ref->type & GIT_REF_PACKED) {
		/* insert the original on the loose cache */
		error = git_hashtable_insert(ref->owner->references.loose_cache, ref->name, ref);
		if (error < GIT_SUCCESS)
			goto cleanup;

		ref->type &= ~GIT_REF_PACKED;

		/* replace the original in the packfile with the copy */
		error = git_hashtable_insert(ref->owner->references.packfile, ref_old->ref.name, ref_old);
		if (error < GIT_SUCCESS)
			goto cleanup;
	}

	return GIT_SUCCESS;

cleanup:
	reference_free((reference *)ref_old);
	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to set OID target of reference");
}

int git_reference_set_oid(git_reference *ref_in, const git_oid *target)
{
	reference *ref;

	ref = reference_get_internal(ref_in);
	if (ref == NULL)
		return git__throw(GIT_ENOTFOUND, "Failed to rename reference. Reference `%s` doesn't exist", ref->name);

	return reference_set_oid(ref, target);
}

/*
 * Change the target of a symbolic reference.
 *
 * This is easy because symrefs cannot be inside
 * a pack. We just change the target in memory
 * and overwrite the file on disk.
 */
int reference_set_target(reference *ref, const char *target)
{
	reference_symbolic *ref_sym;

	if ((ref->type & GIT_REF_SYMBOLIC) == 0)
		return git__throw(GIT_EINVALIDREFSTATE, "Failed to set reference target. Not a symbolic reference");

	ref_sym = (reference_symbolic *)ref;

	git__free(ref_sym->target);
	ref_sym->target = git__strdup(target);
	if (ref_sym->target == NULL)
		return GIT_ENOMEM;

	return loose_write(ref);
}

int git_reference_set_target(git_reference *ref_in, const char *target)
{
	reference *ref;

	ref = reference_get_internal(ref_in);
	if (ref == NULL)
		return git__throw(GIT_ENOTFOUND, "Failed to rename reference. Reference `%s` doesn't exist", ref->name);

	return reference_set_target(ref, target);
}

int git_reference_rename(git_reference *ref_in, const char *new_name, int force)
{
	int error;

	char aux_path[GIT_PATH_MAX];
	char normalized[GIT_REFNAME_MAX];

	const char *head_target = NULL;
	reference *ref = NULL, *new_ref = NULL, *head = NULL, *tmp_ref = NULL;

	assert(ref_in);

	ref = reference_get_internal(ref_in);
	if (ref == NULL)
		return git__throw(GIT_ENOTFOUND, "Failed to rename reference. Reference `%s` doesn't exist", ref->name);

	error = normalize_name(normalized, sizeof(normalized), new_name, ref->type & GIT_REF_OID);
	if (error < GIT_SUCCESS)
		return git__rethrow(error, "Failed to rename reference. Invalid name");

	new_name = normalized;

	error = reference_lookup(&new_ref, ref->owner, new_name);
	if (error == GIT_SUCCESS) {
		if (!force)
			return git__throw(GIT_EEXISTS, "Failed to rename reference. Reference already exists");

		error = reference_delete(new_ref);
	}

	if (error < GIT_SUCCESS) {
		git_path_join(aux_path, ref->owner->path_repository, new_name);
		/* If we couldn't read the reference because it doesn't
		 * exist it's ok - otherwise return */
		if (git_futils_isfile(aux_path) == GIT_SUCCESS)
			goto cleanup;
	}

	if ((error = reference_available(ref->owner, new_name, ref->name)) < GIT_SUCCESS)
		return git__rethrow(error, "Failed to rename reference. Reference already exists");

	/*
	 * First, we backup the reference targets. Just keeping the old
	 * reference won't work, since we may have to remove it to create
	 * the new reference, e.g. when renaming foo/bar -> foo.
	 */

	if (ref->type & GIT_REF_SYMBOLIC)
		tmp_ref = git__malloc(sizeof(reference_symbolic));
	else
		tmp_ref = git__malloc(sizeof(reference_oid));

	if (tmp_ref == NULL)
		return GIT_ENOMEM;

	tmp_ref->name  = git__strdup(ref->name);
	tmp_ref->type  = ref->type;
	tmp_ref->owner = ref->owner;

	if (ref->type & GIT_REF_SYMBOLIC)
		((reference_symbolic *)tmp_ref)->target = git__strdup(((reference_symbolic *)ref)->target);
	else
		((reference_oid *)tmp_ref)->oid = ((reference_oid *)ref)->oid;

	/*
	 * Now delete the old ref and remove an possibly existing directory
	 * named `new_name`.
	 */

	if ((error = reference_delete(ref)) < GIT_SUCCESS)
		goto cleanup;

	git_path_join(aux_path, tmp_ref->owner->path_repository, new_name);
	if (git_futils_exists(aux_path) == GIT_SUCCESS) {
		if (git_futils_isdir(aux_path) == GIT_SUCCESS) {
			if ((error = git_futils_rmdir_r(aux_path, 0)) < GIT_SUCCESS)
				goto rollback;
		} else goto rollback;
	}

	/*
	 * Crude hack: delete any logs till we support proper reflogs.
	 * Otherwise git.git will possibly fail and leave a mess. git.git
	 * writes reflogs by default in any repo with a working directory:
	 *
	 * "We only enable reflogs in repositories that have a working directory
	 * associated with them, as shared/bare repositories do not have
	 * an easy means to prune away old log entries, or may fail logging
	 * entirely if the user's gecos information is not valid during a push.
	 * This heuristic was suggested on the mailing list by Junio."
	 *
	 * 	Shawn O. Pearce - 0bee59186976b1d9e6b2dd77332480c9480131d5
	 *
	 * TODO
	 *
	 */

	git_path_join_n(aux_path, 3, tmp_ref->owner->path_repository, "logs", tmp_ref->name);
	if (git_futils_isfile(aux_path) == GIT_SUCCESS) {
		if ((error = p_unlink(aux_path)) < GIT_SUCCESS)
			goto rollback;
	}

	/*
	 * Finally we can create the new reference.
	 */
	if (tmp_ref->type & GIT_REF_SYMBOLIC) {
		if ((error = reference_create_symbolic(&new_ref, tmp_ref->owner, new_name, ((reference_symbolic *)tmp_ref)->target, 0)) < GIT_SUCCESS)
			goto rollback;
	} else {
		if ((error = reference_create_oid(&new_ref, tmp_ref->owner, new_name, &((reference_oid *)tmp_ref)->oid, 0)) < GIT_SUCCESS)
			goto rollback;
	}

	/*
	 * Change the name of the reference given by the user.
	 */
	git__free(ref_in->name);
	ref_in->name = git__strdup(new_ref->name);

	if ((error = git_hashtable_insert(new_ref->owner->references.loose_cache, new_ref->name, new_ref)) < GIT_SUCCESS)
		goto rollback;

	/*
	 * Check if we have to update HEAD.
	 */

	if ((error = reference_lookup(&head, new_ref->owner, GIT_HEAD_FILE)) < GIT_SUCCESS)
		goto cleanup;

	head_target = ref_target(head);

	if (head_target && !strcmp(head_target, tmp_ref->name))
		if ((error = reference_create_symbolic(&head, new_ref->owner, "HEAD", new_ref->name, 1)) < GIT_SUCCESS)
			goto rollback;

cleanup:
	reference_free(tmp_ref);
	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to rename reference");

rollback:
	/*
	 * Try to create the old reference again.
	 */
	if (ref->type & GIT_REF_SYMBOLIC)
		error = reference_create_symbolic(&new_ref, tmp_ref->owner, tmp_ref->name, ((reference_symbolic *)tmp_ref)->target, 0);
	else
		error = reference_create_oid(&new_ref, ref->owner, tmp_ref->name, &((reference_oid *)tmp_ref)->oid, 0);

	git__free(ref_in->name);
	ref_in->name = git__strdup(tmp_ref->name);

	reference_free(tmp_ref);

	return error == GIT_SUCCESS ?
		git__rethrow(GIT_ERROR, "Failed to rename reference. Did rollback") :
		git__rethrow(error, "Failed to rename reference. Failed to rollback");
}

/*
 * Delete a reference.
 *
 * If the reference is packed, this is an expensive
 * operation. We need to remove the reference from
 * the memory cache and then rewrite the whole pack
 *
 * If the reference is loose, we remove it on
 * the filesystem and update the in-memory cache
 * accordingly. We also make sure that an older version
 * of it doesn't exist as a packed reference. If this
 * is the case, this packed reference is removed as well.
 *
 * This obviously invalidates the `ref` pointer.
 */
int reference_delete(reference *ref)
{
	int error;
	reference *reference;

	assert(ref);

	if (ref->type & GIT_REF_PACKED) {
		/* load the existing packfile */
		if ((error = packed_load(ref->owner)) < GIT_SUCCESS)
			return git__rethrow(error, "Failed to delete reference");

		if (git_hashtable_remove(ref->owner->references.packfile, ref->name) < GIT_SUCCESS)
			return git__throw(GIT_ENOTFOUND, "Reference not found");

		error = packed_write(ref->owner);
	} else {
		char full_path[GIT_PATH_MAX];
		git_path_join(full_path, ref->owner->path_repository, ref->name);
		git_hashtable_remove(ref->owner->references.loose_cache, ref->name);
		error = p_unlink(full_path);
		if (error < GIT_SUCCESS)
			goto cleanup;

		/* When deleting a loose reference, we have to ensure that an older
		 * packed version of it doesn't exist
		 */
		if (!reference_lookup(&reference, ref->owner, ref->name)) {
			assert((reference->type & GIT_REF_PACKED) != 0);
			error = reference_delete(reference);
		}
	}

cleanup:
	reference_free(ref);
	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to delete reference");
}

int git_reference_delete(git_reference *ref_in)
{
	reference *ref;

	ref = reference_get_internal(ref_in);
	if (ref == NULL)
		return git__throw(GIT_ENOTFOUND, "Failed to delete reference. Reference `%s` doesn't exist", ref_in->name);

	git_reference_free(ref_in);

	return reference_delete(ref);
}

static int reference_resolve(reference **resolved_ref, reference *ref)
{
	git_repository *repo;
	int error, i;

	assert(resolved_ref && ref);
	*resolved_ref = NULL;

	if ((error = loose_update(ref)) < GIT_SUCCESS)
		return git__rethrow(error, "Failed to resolve reference");

	repo = ref->owner;

	for (i = 0; i < MAX_NESTING_LEVEL; ++i) {
		reference_symbolic *ref_sym;

		*resolved_ref = ref;

		if (ref->type & GIT_REF_OID)
			return GIT_SUCCESS;

		ref_sym = (reference_symbolic *)ref;
		if ((error = reference_lookup(&ref, repo, ref_sym->target)) < GIT_SUCCESS)
			return error;
	}

	return git__throw(GIT_ENOMEM, "Failed to resolve reference. Reference is too nested");
}

int git_reference_resolve(git_reference **resolved_ref, git_reference *ref_in)
{
	int error;
	reference *ref = NULL, *out = NULL;

	*resolved_ref = NULL;

	ref = reference_get_internal(ref_in);
	if (ref == NULL)
		return git__throw(GIT_ENOTFOUND, "Failed to resolve reference. Reference `%s` doesn't exist", ref_in->name);

	error = reference_resolve(&out, ref);
	if (error < GIT_SUCCESS)
		return error;

	*resolved_ref = reference_create_external(out);
	if (*resolved_ref == NULL)
		return GIT_ENOMEM;

	return GIT_SUCCESS;
}

int git_reference_packall(git_repository *repo)
{
	int error;

	/* load the existing packfile */
	if ((error = packed_load(repo)) < GIT_SUCCESS)
		return git__rethrow(error, "Failed to pack references");

	/* update it in-memory with all the loose references */
	if ((error = packed_loadloose(repo)) < GIT_SUCCESS)
		return git__rethrow(error, "Failed to pack references");

	/* write it back to disk */
	return packed_write(repo);
}

int git_reference_foreach(git_repository *repo, unsigned int list_flags, int (*callback)(const char *, void *), void *payload)
{
	int error;
	struct dirent_list_data data;
	char refs_path[GIT_PATH_MAX];

	/* list all the packed references first */
	if (list_flags & GIT_REF_PACKED) {
		const char *ref_name;
		void *GIT_UNUSED(_unused);

		if ((error = packed_load(repo)) < GIT_SUCCESS)
			return git__rethrow(error, "Failed to list references");

		GIT_HASHTABLE_FOREACH(repo->references.packfile, ref_name, _unused,
			if ((error = callback(ref_name, payload)) < GIT_SUCCESS)
				return git__throw(error, "Failed to list references. User callback failed");
		);
	}

	/* now list the loose references, trying not to
	 * duplicate the ref names already in the packed-refs file */

	data.repo_path_len = strlen(repo->path_repository);
	data.list_flags = list_flags;
	data.repo = repo;
	data.callback = callback;
	data.callback_payload = payload;


	git_path_join(refs_path, repo->path_repository, GIT_REFS_DIR);
	return git_futils_direach(refs_path, GIT_PATH_MAX, _dirent_loose_listall, &data);
}

static int cb__reflist_add(const char *ref, void *data)
{
	return git_vector_insert((git_vector *)data, git__strdup(ref));
}

int git_reference_listall(git_strarray *array, git_repository *repo, unsigned int list_flags)
{
	int error;
	git_vector ref_list;

	assert(array && repo);

	array->strings = NULL;
	array->count = 0;

	if (git_vector_init(&ref_list, 8, NULL) < GIT_SUCCESS)
		return GIT_ENOMEM;

	error = git_reference_foreach(repo, list_flags, &cb__reflist_add, (void *)&ref_list);

	if (error < GIT_SUCCESS) {
		git_vector_free(&ref_list);
		return error;
	}

	array->strings = (char **)ref_list.contents;
	array->count = ref_list.length;
	return GIT_SUCCESS;
}

int git_repository__refcache_init(git_refcache *refs)
{
	assert(refs);

	refs->loose_cache = git_hashtable_alloc(
		default_table_size,
		reftable_hash,
		(git_hash_keyeq_ptr)(&git__strcmp_cb));

	/* packfile loaded lazily */
	refs->packfile = NULL;
	refs->packfile_time = 0;

	return (refs->loose_cache) ? GIT_SUCCESS : GIT_ENOMEM;
}

void git_repository__refcache_free(git_refcache *refs)
{
	reference *reference;
	const void *GIT_UNUSED(_unused);

	assert(refs);

	GIT_HASHTABLE_FOREACH(refs->loose_cache, _unused, reference,
		reference_free(reference);
	);

	git_hashtable_free(refs->loose_cache);

	if (refs->packfile) {
		GIT_HASHTABLE_FOREACH(refs->packfile, _unused, reference,
			reference_free(reference);
		);

		git_hashtable_free(refs->packfile);
	}
}

static int check_valid_ref_char(char ch)
{
	if ((unsigned) ch <= ' ')
		return GIT_ERROR;

	switch (ch) {
	case '~':
	case '^':
	case ':':
	case '\\':
	case '?':
	case '[':
	case '*':
		return GIT_ERROR;
	default:
		return GIT_SUCCESS;
	}
}

static int normalize_name(char *buffer_out, size_t out_size, const char *name, int is_oid_ref)
{
	const char *name_end, *buffer_out_start;
	const char *current;
	int contains_a_slash = 0;

	assert(name && buffer_out);

	buffer_out_start = buffer_out;
	current = name;
	name_end = name + strlen(name);

	/* Terminating null byte */
	out_size--;

	/* A refname can not be empty */
	if (name_end == name)
		return git__throw(GIT_EINVALIDREFNAME, "Failed to normalize name. Reference name is empty");

	/* A refname can not end with a dot or a slash */
	if (*(name_end - 1) == '.' || *(name_end - 1) == '/')
		return git__throw(GIT_EINVALIDREFNAME, "Failed to normalize name. Reference name ends with dot or slash");

	while (current < name_end && out_size) {
		if (check_valid_ref_char(*current))
			return git__throw(GIT_EINVALIDREFNAME, "Failed to normalize name. Reference name contains invalid characters");

		if (buffer_out > buffer_out_start) {
			char prev = *(buffer_out - 1);

			/* A refname can not start with a dot nor contain a double dot */
			if (*current == '.' && ((prev == '.') || (prev == '/')))
				return git__throw(GIT_EINVALIDREFNAME, "Failed to normalize name. Reference name starts with a dot or contains a double dot");

			/* '@{' is forbidden within a refname */
			if (*current == '{' && prev == '@')
				return git__throw(GIT_EINVALIDREFNAME, "Failed to normalize name. Reference name contains '@{'");

			/* Prevent multiple slashes from being added to the output */
			if (*current == '/' && prev == '/') {
				current++;
				continue;
			}
		}

		if (*current == '/')
			contains_a_slash = 1;

		*buffer_out++ = *current++;
		out_size--;
	}

	if (!out_size)
		return git__throw(GIT_EINVALIDREFNAME, "Reference name is too long");

	/* Object id refname have to contain at least one slash, except
	 * for HEAD in a detached state or MERGE_HEAD if we're in the
	 * middle of a merge */
	if (is_oid_ref && !contains_a_slash && (strcmp(name, GIT_HEAD_FILE) && strcmp(name, GIT_MERGE_HEAD_FILE)
	                                        && strcmp(name, GIT_FETCH_HEAD_FILE)))
		return git__throw(GIT_EINVALIDREFNAME, "Failed to normalize name. Reference name contains no slashes");

	/* A refname can not end with ".lock" */
	if (!git__suffixcmp(name, GIT_FILELOCK_EXTENSION))
		return git__throw(GIT_EINVALIDREFNAME, "Failed to normalize name. Reference name ends with '.lock'");

	*buffer_out = '\0';

	/*
	 * For object id references, name has to start with refs/. Again,
	 * we need to allow HEAD to be in a detached state.
	 */
	if (is_oid_ref && !(git__prefixcmp(buffer_out_start, GIT_REFS_DIR) ||
		strcmp(buffer_out_start, GIT_HEAD_FILE)))
		return git__throw(GIT_EINVALIDREFNAME, "Failed to normalize name. Reference name does not start with 'refs/'");

	return GIT_SUCCESS;
}

int git_reference__normalize_name(char *buffer_out, size_t out_size, const char *name)
{
	return normalize_name(buffer_out, out_size, name, 0);
}

int git_reference__normalize_name_oid(char *buffer_out, size_t out_size, const char *name)
{
	return normalize_name(buffer_out, out_size, name, 1);
}