[libgit2.git] / src / revparse.c

/*
 * Copyright (C) 2009-2012 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 <assert.h>

#include "common.h"
#include "buffer.h"
#include "date.h"
#include "tree.h"

#include "git2.h"

GIT_BEGIN_DECL

typedef enum {
   REVPARSE_STATE_INIT,
   REVPARSE_STATE_CARET,
   REVPARSE_STATE_LINEAR,
   REVPARSE_STATE_COLON,
   REVPARSE_STATE_DONE,
} revparse_state;

static void set_invalid_syntax_err(const char *spec)
{
   giterr_set(GITERR_INVALID, "Refspec '%s' is not valid.", spec);
}

static int revparse_lookup_fully_qualifed_ref(git_object **out, git_repository *repo, const char*spec)
{
   git_oid resolved;

   if (git_reference_name_to_oid(&resolved, repo, spec) < 0)
      return GIT_ERROR;

   return git_object_lookup(out, repo, &resolved, GIT_OBJ_ANY);
}

/* Returns non-zero if yes */
static int spec_looks_like_describe_output(const char *spec)
{
   regex_t regex;
   int regex_error, retcode;

   regex_error = regcomp(&regex, ".+-[0-9]+-g[0-9a-fA-F]+", REG_EXTENDED);
   if (regex_error != 0) {
      giterr_set_regex(&regex, regex_error);
      return 1; /* To be safe */
   }
   retcode = regexec(&regex, spec, 0, NULL, 0);
   regfree(&regex);
   return retcode == 0;
}

static int revparse_lookup_object(git_object **out, git_repository *repo, const char *spec)
{
   size_t speclen = strlen(spec);
   git_object *obj = NULL;
   git_oid oid;
   git_buf refnamebuf = GIT_BUF_INIT;
   static const char* formatters[] = {
      "refs/%s",
      "refs/tags/%s",
      "refs/heads/%s",
      "refs/remotes/%s",
      "refs/remotes/%s/HEAD",
      NULL
   };
   unsigned int i;
   const char *substr;

   /* "git describe" output; snip everything before/including "-g" */
   substr = strstr(spec, "-g");
   if (substr &&
       spec_looks_like_describe_output(spec) &&
       !revparse_lookup_object(out, repo, substr+2)) {
      return 0;
   }

   /* SHA or prefix */
   if (!git_oid_fromstrn(&oid, spec, speclen)) {
      if (!git_object_lookup_prefix(&obj, repo, &oid, speclen, GIT_OBJ_ANY)) {
         *out = obj;
         return 0;
      }
   }

   /* Fully-named ref */
   if (!revparse_lookup_fully_qualifed_ref(&obj, repo, spec)) {
      *out = obj;
      return 0;
   }

   /* Partially-named ref; match in this order: */
   for (i=0; formatters[i]; i++) {
      git_buf_clear(&refnamebuf);
      if (git_buf_printf(&refnamebuf, formatters[i], spec) < 0) {
         return GIT_ERROR;
      }

      if (!revparse_lookup_fully_qualifed_ref(&obj, repo, git_buf_cstr(&refnamebuf))) {
         git_buf_free(&refnamebuf);
         *out = obj;
         return 0;
      }
   }
   git_buf_free(&refnamebuf);

   giterr_set(GITERR_REFERENCE, "Refspec '%s' not found.", spec);
   return GIT_ERROR;
}


static int all_chars_are_digits(const char *str, size_t len)
{
   size_t i=0;
   for (i=0; i<len; i++) {
      if (str[i] < '0' || str[i] > '9') return 0;
   }
   return 1;
}

static void normalize_maybe_empty_refname(git_buf *buf, git_repository *repo, const char *refspec, size_t refspeclen)
{
   git_reference *ref;

   if (!refspeclen) {
      /* Empty refspec means current branch (target of HEAD) */
      git_reference_lookup(&ref, repo, "HEAD");
      git_buf_puts(buf, git_reference_target(ref));
      git_reference_free(ref);
   } else if (strstr(refspec, "HEAD")) {
      /* Explicit head */
      git_buf_puts(buf, refspec);
   }else {
      if (git__prefixcmp(refspec, "refs/heads/") != 0) {
         git_buf_printf(buf, "refs/heads/%s", refspec);
      } else {
         git_buf_puts(buf, refspec);
      }
   }
}

static int walk_ref_history(git_object **out, git_repository *repo, const char *refspec, const char *reflogspec)
{
   git_reference *ref;
   git_reflog *reflog = NULL;
   int n, retcode = GIT_ERROR;
   int i, refloglen;
   const git_reflog_entry *entry;
   git_buf buf = GIT_BUF_INIT;
   size_t refspeclen = strlen(refspec);
   size_t reflogspeclen = strlen(reflogspec);

   if (git__prefixcmp(reflogspec, "@{") != 0 ||
       git__suffixcmp(reflogspec, "}") != 0) {
      giterr_set(GITERR_INVALID, "Bad reflogspec '%s'", reflogspec);
      return GIT_ERROR;
   }

   /* "@{-N}" form means walk back N checkouts. That means the HEAD log. */
   if (refspeclen == 0 && !git__prefixcmp(reflogspec, "@{-")) {
      regex_t regex;
      int regex_error;

      if (git__strtol32(&n, reflogspec+3, NULL, 0) < 0 ||
          n < 1) {
         giterr_set(GITERR_INVALID, "Invalid reflogspec %s", reflogspec);
         return GIT_ERROR;
      }

      if (!git_reference_lookup(&ref, repo, "HEAD")) {
         if (!git_reflog_read(&reflog, ref)) {
            regex_error = regcomp(&regex, "checkout: moving from (.*) to .*", REG_EXTENDED);
            if (regex_error != 0) {
               giterr_set_regex(&regex, regex_error);
            } else {
               regmatch_t regexmatches[2];

               refloglen = git_reflog_entrycount(reflog);
               for (i=refloglen-1; i >= 0; i--) {
                  const char *msg;
                  entry = git_reflog_entry_byindex(reflog, i);

                  msg = git_reflog_entry_msg(entry);
                  if (!regexec(&regex, msg, 2, regexmatches, 0)) {
                     n--;
                     if (!n) {
                        git_buf_put(&buf, msg+regexmatches[1].rm_so, regexmatches[1].rm_eo - regexmatches[1].rm_so);
                        retcode = revparse_lookup_object(out, repo, git_buf_cstr(&buf));
                        break;
                     }
                  }
               }
               regfree(&regex);
            }
         }
         git_reference_free(ref);
      }
   } else {
      int date_error = 0;
      git_time_t timestamp;
      git_buf datebuf = GIT_BUF_INIT;

      git_buf_put(&datebuf, reflogspec+2, reflogspeclen-3);
      date_error = git__date_parse(&timestamp, git_buf_cstr(&datebuf));

      /* @{u} or @{upstream} -> upstream branch, for a tracking branch. This is stored in the config. */
      if (!strcmp(reflogspec, "@{u}") || !strcmp(reflogspec, "@{upstream}")) {
         git_config *cfg;
         if (!git_repository_config(&cfg, repo)) {
            /* Is the ref a tracking branch? */
            const char *remote;
            git_buf_clear(&buf);
            git_buf_printf(&buf, "branch.%s.remote", refspec);
            if (!git_config_get_string(cfg, git_buf_cstr(&buf), &remote)) {
               /* Yes. Find the first merge target name. */
               const char *mergetarget;
               git_buf_clear(&buf);
               git_buf_printf(&buf, "branch.%s.merge", refspec);
               if (!git_config_get_string(cfg, git_buf_cstr(&buf), &mergetarget) &&
                   !git__prefixcmp(mergetarget, "refs/heads/")) {
                  /* Success. Look up the target and fetch the object. */
                  git_buf_clear(&buf);
                  git_buf_printf(&buf, "refs/remotes/%s/%s", remote, mergetarget+11);
                  retcode = revparse_lookup_fully_qualifed_ref(out, repo, git_buf_cstr(&buf));
               }
            }
            git_config_free(cfg);
         }
      }

      /* @{N} -> Nth prior value for the ref (from reflog) */
      else if (all_chars_are_digits(reflogspec+2, reflogspeclen-3) &&
               !git__strtol32(&n, reflogspec+2, NULL, 0) &&
               n <= 100000000) { /* Allow integer time */
         normalize_maybe_empty_refname(&buf, repo, refspec, refspeclen);

         if (n == 0) {
            retcode = revparse_lookup_fully_qualifed_ref(out, repo, git_buf_cstr(&buf));
         } else if (!git_reference_lookup(&ref, repo, git_buf_cstr(&buf))) {
            if (!git_reflog_read(&reflog, ref)) {
               int numentries = git_reflog_entrycount(reflog);
               if (numentries < n) {
                  giterr_set(GITERR_REFERENCE, "Reflog for '%s' has only %d entries, asked for %d",
                             git_buf_cstr(&buf), numentries, n);
                  retcode = GIT_ERROR;
               } else {
                  const git_reflog_entry *entry = git_reflog_entry_byindex(reflog, n);
                  const git_oid *oid = git_reflog_entry_oidold(entry);
                  retcode = git_object_lookup(out, repo, oid, GIT_OBJ_ANY);
               }
            }
            git_reference_free(ref);
         }
      }

      else if (!date_error) {
         /* Ref as it was on a certain date */
         normalize_maybe_empty_refname(&buf, repo, refspec, refspeclen);

         if (!git_reference_lookup(&ref, repo, git_buf_cstr(&buf))) {
            git_reflog *reflog;
            if (!git_reflog_read(&reflog, ref)) {
               /* Keep walking until we find an entry older than the given date */
               int numentries = git_reflog_entrycount(reflog);
               int i;

               /* TODO: clunky. Factor "now" into a utility */
               git_signature *sig;
               git_time as_of;

               git_signature_now(&sig, "blah", "blah");
               as_of = sig->when;
               git_signature_free(sig);

               as_of.time = (timestamp > 0)
                  ? timestamp
                  : sig->when.time + timestamp;

               for (i=numentries-1; i>0; i--) {
                  const git_reflog_entry *entry = git_reflog_entry_byindex(reflog, i);
                  git_time commit_time = git_reflog_entry_committer(entry)->when;
                  if (git__time_cmp(&commit_time, &as_of) <= 0 ) {
                     retcode = git_object_lookup(out, repo, git_reflog_entry_oidnew(entry), GIT_OBJ_ANY);
                     break;
                  }
               }

               if (!i) {
                  /* Didn't find a match. Use the oldest revision in the reflog. */
                  const git_reflog_entry *entry = git_reflog_entry_byindex(reflog, 0);
                  retcode = git_object_lookup(out, repo, git_reflog_entry_oidnew(entry), GIT_OBJ_ANY);
               }

               git_reflog_free(reflog);
            }

            git_reference_free(ref);
         }
      }

      git_buf_free(&datebuf);
   }

   if (reflog) git_reflog_free(reflog);
   git_buf_free(&buf);
   return retcode;
}

static git_object* dereference_object(git_object *obj)
{
   git_otype type = git_object_type(obj);

   switch (type) {
   case GIT_OBJ_COMMIT:
      {
         git_tree *tree = NULL;
         if (0 == git_commit_tree(&tree, (git_commit*)obj)) {
            return (git_object*)tree;
         }
      }
      break;
   case GIT_OBJ_TAG:
      {
            git_object *newobj = NULL;
            if (0 == git_tag_target(&newobj, (git_tag*)obj)) {
               return newobj;
            }
      }
      break;

   default:
   case GIT_OBJ_TREE:
   case GIT_OBJ_BLOB:
   case GIT_OBJ_OFS_DELTA:
   case GIT_OBJ_REF_DELTA:
      break;
   }

   /* Can't dereference some types */
   return NULL;
}

static int dereference_to_type(git_object **out, git_object *obj, git_otype target_type)
{
   int retcode = 1;
   git_object *obj1 = obj, *obj2 = obj;

   while (retcode > 0) {
      git_otype this_type = git_object_type(obj1);

      if (this_type == target_type) {
         *out = obj1;
         retcode = 0;
      } else {
         /* Dereference once, if possible. */
         obj2 = dereference_object(obj1);
         if (!obj2) {
            giterr_set(GITERR_REFERENCE, "Can't dereference to type");
            retcode = GIT_ERROR;
         }
      }
      if (obj1 != obj && obj1 != obj2) {
         git_object_free(obj1);
      }
      obj1 = obj2;
   }
   return retcode;
}

static git_otype parse_obj_type(const char *str)
{
   if (!strcmp(str, "{commit}")) return GIT_OBJ_COMMIT;
   if (!strcmp(str, "{tree}")) return GIT_OBJ_TREE;
   if (!strcmp(str, "{blob}")) return GIT_OBJ_BLOB;
   if (!strcmp(str, "{tag}")) return GIT_OBJ_TAG;
   return GIT_OBJ_BAD;
}

static int handle_caret_syntax(git_object **out, git_repository *repo, git_object *obj, const char *movement)
{
   git_commit *commit;
   size_t movementlen = strlen(movement);
   int n;

   if (*movement == '{') {
      if (movement[movementlen-1] != '}') {
         set_invalid_syntax_err(movement);
         return GIT_ERROR;
      }

      /* {} -> Dereference until we reach an object that isn't a tag. */
      if (movementlen == 2) {
         git_object *newobj = obj;
         git_object *newobj2 = newobj;
         while (git_object_type(newobj2) == GIT_OBJ_TAG) {
            newobj2 = dereference_object(newobj);
            if (newobj != obj) git_object_free(newobj);
            if (!newobj2) {
               giterr_set(GITERR_REFERENCE, "Couldn't find object of target type.");
               return GIT_ERROR;
            }
            newobj = newobj2;
         }
         *out = newobj2;
         return 0;
      }
      
      /* {/...} -> Walk all commits until we see a commit msg that matches the phrase. */
      if (movement[1] == '/') {
         int retcode = GIT_ERROR;
         git_revwalk *walk;
         if (!git_revwalk_new(&walk, repo)) {
            git_oid oid;
            regex_t preg;
            int reg_error;
            git_buf buf = GIT_BUF_INIT;

            git_revwalk_sorting(walk, GIT_SORT_TIME);
            git_revwalk_push(walk, git_object_id(obj));

            /* Extract the regex from the movement string */
            git_buf_put(&buf, movement+2, strlen(movement)-3);

            reg_error = regcomp(&preg, git_buf_cstr(&buf), REG_EXTENDED);
            if (reg_error != 0) {
               giterr_set_regex(&preg, reg_error);
            } else {
               while(!git_revwalk_next(&oid, walk)) {
                  git_object *walkobj;
                  char str[41];
                  git_oid_fmt(str, &oid);
                  str[40] = 0;

                  /* Fetch the commit object, and check for matches in the message */
                  if (!git_object_lookup(&walkobj, repo, &oid, GIT_OBJ_COMMIT)) {
                     if (!regexec(&preg, git_commit_message((git_commit*)walkobj), 0, NULL, 0)) {
                        /* Found it! */
                        retcode = 0;
                        *out = walkobj;
                        if (obj == walkobj) {
                           /* Avoid leaking an object */
                           git_object_free(walkobj);
                        }
                        break;
                     }
                     git_object_free(walkobj);
                  }
               }
               if (retcode < 0) {
                  giterr_set(GITERR_REFERENCE, "Couldn't find a match for %s", movement);
               }
               regfree(&preg);
            }

            git_buf_free(&buf);
            git_revwalk_free(walk);
         }
         return retcode;
      }

      /* {...} -> Dereference until we reach an object of a certain type. */
      if (dereference_to_type(out, obj, parse_obj_type(movement)) < 0) {
         return GIT_ERROR;
      }
      return 0;
   }

   /* Dereference until we reach a commit. */
   if (dereference_to_type(&obj, obj, GIT_OBJ_COMMIT) < 0) {
      /* Can't dereference to a commit; fail */
      return GIT_ERROR;
   }

   /* "^" is the same as "^1" */
   if (movementlen == 0) {
      n = 1;
   } else {
      git__strtol32(&n, movement, NULL, 0);
   }
   commit = (git_commit*)obj;

   /* "^0" just returns the input */
   if (n == 0) {
      *out = obj;
      return 0;
   }

   if (git_commit_parent(&commit, commit, n-1) < 0) {
      return GIT_ERROR;
   }

   *out = (git_object*)commit;
   return 0;
}

static int handle_linear_syntax(git_object **out, git_object *obj, const char *movement)
{
   git_commit *commit1, *commit2;
   int i, n;

   /* Dereference until we reach a commit. */
   if (dereference_to_type(&obj, obj, GIT_OBJ_COMMIT) < 0) {
      /* Can't dereference to a commit; fail */
      return GIT_ERROR;
   }

   /* "~" is the same as "~1" */
   if (strlen(movement) == 0) {
      n = 1;
   } else {
      git__strtol32(&n, movement, NULL, 0);
   }
   commit1 = (git_commit*)obj;

   /* "~0" just returns the input */
   if (n == 0) {
      *out = obj;
      return 0;
   }

   for (i=0; i<n; i++) {
      if (git_commit_parent(&commit2, commit1, 0) < 0) {
         return GIT_ERROR;
      }
      if (commit1 != (git_commit*)obj) {
         git_commit_free(commit1);
      }
      commit1 = commit2;
   }

   *out = (git_object*)commit1;
   return 0;
}

static const git_tree_entry* git_tree_entry_bypath(git_tree *tree, git_repository *repo, const char *path)
{
   char *str = git__strdup(path);
   char *tok;
   void *alloc = str;
   git_tree *tree2 = tree;
   const git_tree_entry *entry;

   while ((tok = git__strtok(&str, "/\\")) != NULL) {
      entry = git_tree_entry_byname(tree2, tok);
      if (tree2 != tree) git_tree_free(tree2);
      if (entry_is_tree(entry)) {
         if (git_tree_lookup(&tree2, repo, &entry->oid) < 0) {
            free(alloc);
            return NULL;
         }
      }
   }

   free(alloc);
   return entry;
}

static int handle_colon_syntax(git_object **out,
                               git_repository *repo,
                               git_object *obj,
                               const char *path)
{
   git_tree *tree;
   const git_tree_entry *entry;

   /* Dereference until we reach a tree. */
   if (dereference_to_type(&obj, obj, GIT_OBJ_TREE) < 0) {
      return GIT_ERROR;
   }
   tree = (git_tree*)obj;

   /* Find the blob at the given path. */
   entry = git_tree_entry_bypath(tree, repo, path);
   git_tree_free(tree);
   return git_tree_entry_2object(out, repo, entry);
}

int git_revparse_single(git_object **out, git_repository *repo, const char *spec)
{
   revparse_state current_state = REVPARSE_STATE_INIT,  next_state = REVPARSE_STATE_INIT;
   const char *spec_cur = spec;
   git_object *cur_obj = NULL,  *next_obj = NULL;
   git_buf specbuffer = GIT_BUF_INIT,  stepbuffer = GIT_BUF_INIT;
   int retcode = 0;

   assert(out && repo && spec);

   if (spec[0] == ':') {
      /* Either a global grep (":/foo") or a merge-stage path lookup (":2:Makefile").
         Neither of these are handled just yet. */
      giterr_set(GITERR_INVALID, "Unimplemented");
      return GIT_ERROR;
   }

   while (current_state != REVPARSE_STATE_DONE) {
      switch (current_state) {
      case REVPARSE_STATE_INIT:
         if (!*spec_cur) {
            /* No operators, just a name. Find it and return. */
            retcode = revparse_lookup_object(out, repo, spec);
            next_state = REVPARSE_STATE_DONE;
         } else if (*spec_cur == '@') {
            /* '@' syntax doesn't allow chaining */
            git_buf_puts(&stepbuffer, spec_cur);
            retcode = walk_ref_history(out, repo, git_buf_cstr(&specbuffer), git_buf_cstr(&stepbuffer));
            next_state = REVPARSE_STATE_DONE;
         } else if (*spec_cur == '^') {
            next_state = REVPARSE_STATE_CARET;
         } else if (*spec_cur == '~') {
            next_state = REVPARSE_STATE_LINEAR;
         } else if (*spec_cur == ':') {
            next_state = REVPARSE_STATE_COLON;
         } else {
            git_buf_putc(&specbuffer, *spec_cur);
         }
         spec_cur++;

         if (current_state != next_state && next_state != REVPARSE_STATE_DONE) {
            /* Leaving INIT state, find the object specified, in case that state needs it */
            if (revparse_lookup_object(&next_obj, repo, git_buf_cstr(&specbuffer)) < 0) {
               retcode = GIT_ERROR;
               next_state = REVPARSE_STATE_DONE;
            }
         }
         break;


      case REVPARSE_STATE_CARET:
         /* Gather characters until NULL, '~', or '^' */
         if (!*spec_cur) {
            retcode = handle_caret_syntax(out, repo, cur_obj, git_buf_cstr(&stepbuffer));
            next_state = REVPARSE_STATE_DONE;
         } else if (*spec_cur == '~') {
            retcode = handle_caret_syntax(&next_obj, repo, cur_obj, git_buf_cstr(&stepbuffer));
            git_buf_clear(&stepbuffer);
            next_state = !retcode ? REVPARSE_STATE_LINEAR : REVPARSE_STATE_DONE;
         } else if (*spec_cur == '^') {
            retcode = handle_caret_syntax(&next_obj, repo, cur_obj, git_buf_cstr(&stepbuffer));
            git_buf_clear(&stepbuffer);
            if (retcode < 0) {
               next_state = REVPARSE_STATE_DONE;
            }
         } else {
            git_buf_putc(&stepbuffer, *spec_cur);
         }
         spec_cur++;
         break;

      case REVPARSE_STATE_LINEAR:
         if (!*spec_cur) {
            retcode = handle_linear_syntax(out, cur_obj, git_buf_cstr(&stepbuffer));
            next_state = REVPARSE_STATE_DONE;
         } else if (*spec_cur == '~') {
            retcode = handle_linear_syntax(&next_obj, cur_obj, git_buf_cstr(&stepbuffer));
            git_buf_clear(&stepbuffer);
            if (retcode < 0) {
               next_state = REVPARSE_STATE_DONE;
            }
         } else if (*spec_cur == '^') {
            retcode = handle_linear_syntax(&next_obj, cur_obj, git_buf_cstr(&stepbuffer));
            git_buf_clear(&stepbuffer);
            next_state = !retcode ? REVPARSE_STATE_CARET : REVPARSE_STATE_DONE;
         } else {
            git_buf_putc(&stepbuffer, *spec_cur);
         }
         spec_cur++;
         break;

      case REVPARSE_STATE_COLON:
         if (*spec_cur) {
            git_buf_putc(&stepbuffer, *spec_cur);
         } else {
            retcode = handle_colon_syntax(out, repo, cur_obj, git_buf_cstr(&stepbuffer));
            next_state = REVPARSE_STATE_DONE;
         }
         spec_cur++;
         break;

      case REVPARSE_STATE_DONE:
         if (cur_obj && *out != cur_obj) git_object_free(cur_obj);
         if (next_obj && *out != next_obj) git_object_free(next_obj);
         break;
      }

      current_state = next_state;
      if (cur_obj != next_obj) {
         if (cur_obj) git_object_free(cur_obj);
         cur_obj = next_obj;
      }
   }

   if (*out != cur_obj) git_object_free(cur_obj);
   if (*out != next_obj && next_obj != cur_obj) git_object_free(next_obj);

   git_buf_free(&specbuffer);
   git_buf_free(&stepbuffer);
   return retcode;
}


GIT_END_DECL