Merge branch 'maint'
[gitweb.git] / merge-recursive.c
index 5d20f9efce54224d9461f6451a049066b5d75232..2ba43ae84b20f993ba175f728297cf5360066872 100644 (file)
 #include "diffcore.h"
 #include "run-command.h"
 #include "tag.h"
-
+#include "unpack-trees.h"
 #include "path-list.h"
 
-/*#define DEBUG*/
-
-#ifdef DEBUG
-#define debug(...) fprintf(stderr, __VA_ARGS__)
-#else
-#define debug(...) do { ; /* nothing */ } while (0)
-#endif
-
-#ifdef DEBUG
-#include "quote.h"
-static void show_ce_entry(const char *tag, struct cache_entry *ce)
-{
-       if (tag && *tag &&
-           (ce->ce_flags & htons(CE_VALID))) {
-               static char alttag[4];
-               memcpy(alttag, tag, 3);
-               if (isalpha(tag[0]))
-                       alttag[0] = tolower(tag[0]);
-               else if (tag[0] == '?')
-                       alttag[0] = '!';
-               else {
-                       alttag[0] = 'v';
-                       alttag[1] = tag[0];
-                       alttag[2] = ' ';
-                       alttag[3] = 0;
-               }
-               tag = alttag;
-       }
-
-       fprintf(stderr,"%s%06o %s %d\t",
-                       tag,
-                       ntohl(ce->ce_mode),
-                       sha1_to_hex(ce->sha1),
-                       ce_stage(ce));
-       write_name_quoted("", 0, ce->name,
-                       '\n', stderr);
-       fputc('\n', stderr);
-}
-
-static void ls_files(void) {
-       int i;
-       for (i = 0; i < active_nr; i++) {
-               struct cache_entry *ce = active_cache[i];
-               show_ce_entry("", ce);
-       }
-       fprintf(stderr, "---\n");
-       if (0) ls_files(); /* avoid "unused" warning */
-}
-#endif
-
 /*
  * A virtual commit has
  * - (const char *)commit->util set to the name, and
@@ -93,24 +43,25 @@ static struct commit *make_virtual_commit(struct tree *tree, const char *comment
        commit->tree = tree;
        commit->util = (void*)comment;
        *(int*)commit->object.sha1 = virtual_id++;
+       /* avoid warnings */
+       commit->object.parsed = 1;
        return commit;
 }
 
 /*
- * TODO: we should not have to copy the SHA1s around, but rather reference
- * them. That way, sha_eq() is just sha1 == sha2.
+ * Since we use get_tree_entry(), which does not put the read object into
+ * the object pool, we cannot rely on a == b.
  */
 static int sha_eq(const unsigned char *a, const unsigned char *b)
 {
        if (!a && !b)
                return 2;
-       return a && b && memcmp(a, b, 20) == 0;
+       return a && b && hashcmp(a, b) == 0;
 }
 
 /*
- * TODO: check if we can just reuse the active_cache structure: it is already
- * sorted (by name, stage).
- * Only problem: do not write it when flushing the cache.
+ * Since we want to write the index eventually, we cannot reuse the index
+ * for these (temporary) data.
  */
 struct stage_data
 {
@@ -165,6 +116,7 @@ static void output_commit_title(struct commit *commit)
        }
 }
 
+static const char *current_index_file = NULL;
 static const char *original_index_file;
 static const char *temporary_index_file;
 static int cache_dirty = 0;
@@ -173,12 +125,10 @@ static int flush_cache(void)
 {
        /* flush temporary index */
        struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
-       int fd = hold_lock_file_for_update(lock, getenv("GIT_INDEX_FILE"));
-       if (fd < 0)
-               die("could not lock %s", temporary_index_file);
+       int fd = hold_lock_file_for_update(lock, current_index_file, 1);
        if (write_cache(fd, active_cache, active_nr) ||
                        close(fd) || commit_lock_file(lock))
-               die ("unable to write %s", getenv("GIT_INDEX_FILE"));
+               die ("unable to write %s", current_index_file);
        discard_cache();
        cache_dirty = 0;
        return 0;
@@ -186,11 +136,12 @@ static int flush_cache(void)
 
 static void setup_index(int temp)
 {
-       const char *idx = temp ? temporary_index_file: original_index_file;
-       if (cache_dirty)
-               die("fatal: cache changed flush_cache();");
+       current_index_file = temp ? temporary_index_file: original_index_file;
+       if (cache_dirty) {
+               discard_cache();
+               cache_dirty = 0;
+       }
        unlink(temporary_index_file);
-       setenv("GIT_INDEX_FILE", idx, 1);
        discard_cache();
 }
 
@@ -207,7 +158,7 @@ static struct cache_entry *make_cache_entry(unsigned int mode,
        size = cache_entry_size(len);
        ce = xcalloc(1, size);
 
-       memcpy(ce->sha1, sha1, 20);
+       hashcpy(ce->sha1, sha1);
        memcpy(ce->name, path, len);
        ce->ce_flags = create_ce_flags(len, stage);
        ce->ce_mode = create_ce_mode(mode);
@@ -223,7 +174,7 @@ static int add_cacheinfo(unsigned int mode, const unsigned char *sha1,
 {
        struct cache_entry *ce;
        if (!cache_dirty)
-               read_cache_from(getenv("GIT_INDEX_FILE"));
+               read_cache_from(current_index_file);
        cache_dirty++;
        ce = make_cache_entry(mode, sha1 ? sha1 : null_sha1, path, stage, refresh);
        if (!ce)
@@ -242,86 +193,89 @@ static int add_cacheinfo(unsigned int mode, const unsigned char *sha1,
  */
 static int index_only = 0;
 
-/*
- * TODO: this can be streamlined by refactoring builtin-read-tree.c
- */
-static int git_read_tree(const struct tree *tree)
+static int git_read_tree(struct tree *tree)
 {
-#if 0
-       fprintf(stderr, "GIT_INDEX_FILE='%s' git-read-tree %s\n",
-               getenv("GIT_INDEX_FILE"),
-               sha1_to_hex(tree->object.sha1));
-#endif
        int rc;
-       const char *argv[] = { "git-read-tree", NULL, NULL, };
+       struct object_list *trees = NULL;
+       struct unpack_trees_options opts;
+
        if (cache_dirty)
                die("read-tree with dirty cache");
-       argv[1] = sha1_to_hex(tree->object.sha1);
-       rc = run_command_v(2, argv);
-       return rc < 0 ? -1: rc;
+
+       memset(&opts, 0, sizeof(opts));
+       object_list_append(&tree->object, &trees);
+       rc = unpack_trees(trees, &opts);
+       cache_tree_free(&active_cache_tree);
+
+       if (rc == 0)
+               cache_dirty = 1;
+
+       return rc;
 }
 
-/*
- * TODO: this can be streamlined by refactoring builtin-read-tree.c
- */
-static int git_merge_trees(const char *update_arg,
+static int git_merge_trees(int index_only,
                           struct tree *common,
                           struct tree *head,
                           struct tree *merge)
 {
-#if 0
-       fprintf(stderr, "GIT_INDEX_FILE='%s' git-read-tree %s -m %s %s %s\n",
-               getenv("GIT_INDEX_FILE"),
-               update_arg,
-               sha1_to_hex(common->object.sha1),
-               sha1_to_hex(head->object.sha1),
-               sha1_to_hex(merge->object.sha1));
-#endif
        int rc;
-       const char *argv[] = {
-               "git-read-tree", NULL, "-m", NULL, NULL, NULL,
-               NULL,
-       };
-       if (cache_dirty)
-               flush_cache();
-       argv[1] = update_arg;
-       argv[3] = sha1_to_hex(common->object.sha1);
-       argv[4] = sha1_to_hex(head->object.sha1);
-       argv[5] = sha1_to_hex(merge->object.sha1);
-       rc = run_command_v(6, argv);
-       return rc < 0 ? -1: rc;
+       struct object_list *trees = NULL;
+       struct unpack_trees_options opts;
+
+       if (!cache_dirty) {
+               read_cache_from(current_index_file);
+               cache_dirty = 1;
+       }
+
+       memset(&opts, 0, sizeof(opts));
+       if (index_only)
+               opts.index_only = 1;
+       else
+               opts.update = 1;
+       opts.merge = 1;
+       opts.head_idx = 2;
+       opts.fn = threeway_merge;
+
+       object_list_append(&common->object, &trees);
+       object_list_append(&head->object, &trees);
+       object_list_append(&merge->object, &trees);
+
+       rc = unpack_trees(trees, &opts);
+       cache_tree_free(&active_cache_tree);
+
+       cache_dirty = 1;
+
+       return rc;
 }
 
-/*
- * TODO: this can be streamlined by refactoring builtin-write-tree.c
- */
 static struct tree *git_write_tree(void)
 {
-#if 0
-       fprintf(stderr, "GIT_INDEX_FILE='%s' git-write-tree\n",
-               getenv("GIT_INDEX_FILE"));
-#endif
-       FILE *fp;
-       int rc;
-       char buf[41];
-       unsigned char sha1[20];
-       int ch;
-       unsigned i = 0;
-       if (cache_dirty)
-               flush_cache();
-       fp = popen("git-write-tree 2>/dev/null", "r");
-       while ((ch = fgetc(fp)) != EOF)
-               if (i < sizeof(buf)-1 && ch >= '0' && ch <= 'f')
-                       buf[i++] = ch;
-               else
-                       break;
-       rc = pclose(fp);
-       if (rc == -1 || WEXITSTATUS(rc))
-               return NULL;
-       buf[i] = '\0';
-       if (get_sha1(buf, sha1) != 0)
-               return NULL;
-       return lookup_tree(sha1);
+       struct tree *result = NULL;
+
+       if (cache_dirty) {
+               unsigned i;
+               for (i = 0; i < active_nr; i++) {
+                       struct cache_entry *ce = active_cache[i];
+                       if (ce_stage(ce))
+                               return NULL;
+               }
+       } else
+               read_cache_from(current_index_file);
+
+       if (!active_cache_tree)
+               active_cache_tree = cache_tree();
+
+       if (!cache_tree_fully_valid(active_cache_tree) &&
+                       cache_tree_update(active_cache_tree,
+                               active_cache, active_nr, 0, 0) < 0)
+               die("error building trees");
+
+       result = lookup_tree(active_cache_tree->sha1);
+
+       flush_cache();
+       cache_dirty = 0;
+
+       return result;
 }
 
 static int save_files_dirs(const unsigned char *sha1,
@@ -329,7 +283,7 @@ static int save_files_dirs(const unsigned char *sha1,
                unsigned int mode, int stage)
 {
        int len = strlen(path);
-       char *newpath = malloc(baselen + len + 1);
+       char *newpath = xmalloc(baselen + len + 1);
        memcpy(newpath, base, baselen);
        memcpy(newpath + baselen, path, len);
        newpath[baselen + len] = '\0';
@@ -346,13 +300,9 @@ static int save_files_dirs(const unsigned char *sha1,
 static int get_files_dirs(struct tree *tree)
 {
        int n;
-       debug("get_files_dirs ...\n");
-       if (read_tree_recursive(tree, "", 0, 0, NULL, save_files_dirs) != 0) {
-               debug("  get_files_dirs done (0)\n");
+       if (read_tree_recursive(tree, "", 0, 0, NULL, save_files_dirs) != 0)
                return 0;
-       }
        n = current_file_set.nr + current_directory_set.nr;
-       debug("  get_files_dirs done (%d)\n", n);
        return n;
 }
 
@@ -388,7 +338,7 @@ static struct path_list *get_unmerged(void)
 
        unmerged->strdup_paths = 1;
        if (!cache_dirty) {
-               read_cache_from(getenv("GIT_INDEX_FILE"));
+               read_cache_from(current_index_file);
                cache_dirty++;
        }
        for (i = 0; i < active_nr; i++) {
@@ -405,7 +355,7 @@ static struct path_list *get_unmerged(void)
                }
                e = item->util;
                e->stages[ce_stage(ce)].mode = ntohl(ce->ce_mode);
-               memcpy(e->stages[ce_stage(ce)].sha, ce->sha1, 20);
+               hashcpy(e->stages[ce_stage(ce)].sha, ce->sha1);
        }
 
        return unmerged;
@@ -434,11 +384,6 @@ static struct path_list *get_renames(struct tree *tree,
        int i;
        struct path_list *renames;
        struct diff_options opts;
-#ifdef DEBUG
-       time_t t = time(0);
-
-       debug("get_renames ...\n");
-#endif
 
        renames = xcalloc(1, sizeof(struct path_list));
        diff_setup(&opts);
@@ -479,9 +424,6 @@ static struct path_list *get_renames(struct tree *tree,
        opts.output_format = DIFF_FORMAT_NO_OUTPUT;
        diff_queued_diff.nr = 0;
        diff_flush(&opts);
-#ifdef DEBUG
-       debug("  get_renames done in %ld\n", time(0)-t);
-#endif
        return renames;
 }
 
@@ -513,7 +455,7 @@ static int remove_path(const char *name)
        if (ret)
                return ret;
        len = strlen(name);
-       dirs = malloc(len+1);
+       dirs = xmalloc(len+1);
        memcpy(dirs, name, len);
        dirs[len] = '\0';
        while ((slash = strrchr(name, '/'))) {
@@ -526,10 +468,6 @@ static int remove_path(const char *name)
        return ret;
 }
 
-/*
- * TODO: once we no longer call external programs, we'd probably be better off
- * not setting / getting the environment variable GIT_INDEX_FILE all the time.
- */
 int remove_file(int clean, const char *path)
 {
        int update_cache = index_only || clean;
@@ -537,7 +475,7 @@ int remove_file(int clean, const char *path)
 
        if (update_cache) {
                if (!cache_dirty)
-                       read_cache_from(getenv("GIT_INDEX_FILE"));
+                       read_cache_from(current_index_file);
                cache_dirty++;
                if (remove_file_from_cache(path))
                        return -1;
@@ -557,9 +495,9 @@ static char *unique_path(const char *path, const char *branch)
        char *newpath = xmalloc(strlen(path) + 1 + strlen(branch) + 8 + 1);
        int suffix = 0;
        struct stat st;
-       char *p = newpath + strlen(newpath);
+       char *p = newpath + strlen(path);
        strcpy(newpath, path);
-       strcat(newpath, "~");
+       *(p++) = '~';
        strcpy(p, branch);
        for (; *p; ++p)
                if ('/' == *p)
@@ -575,8 +513,8 @@ static char *unique_path(const char *path, const char *branch)
 
 static int mkdir_p(const char *path, unsigned long mode)
 {
-       /* path points to cache entries, so strdup before messing with it */
-       char *buf = strdup(path);
+       /* path points to cache entries, so xstrdup before messing with it */
+       char *buf = xstrdup(path);
        int result = safe_create_leading_directories(buf);
        free(buf);
        return result;
@@ -634,7 +572,7 @@ void update_file_flags(const unsigned char *sha,
                        flush_buffer(fd, buf, size);
                        close(fd);
                } else if (S_ISLNK(mode)) {
-                       char *lnk = malloc(size + 1);
+                       char *lnk = xmalloc(size + 1);
                        memcpy(lnk, buf, size);
                        lnk[size] = '\0';
                        mkdir_p(path, 0777);
@@ -688,7 +626,7 @@ static char *git_unpack_file(const unsigned char *sha1, char *path)
 
 static struct merge_file_info merge_file(struct diff_filespec *o,
                struct diff_filespec *a, struct diff_filespec *b,
-               const char *branch1Name, const char *branch2Name)
+               const char *branch1, const char *branch2)
 {
        struct merge_file_info result;
        result.merge = 0;
@@ -698,10 +636,10 @@ static struct merge_file_info merge_file(struct diff_filespec *o,
                result.clean = 0;
                if (S_ISREG(a->mode)) {
                        result.mode = a->mode;
-                       memcpy(result.sha, a->sha1, 20);
+                       hashcpy(result.sha, a->sha1);
                } else {
                        result.mode = b->mode;
-                       memcpy(result.sha, b->sha1, 20);
+                       hashcpy(result.sha, b->sha1);
                }
        } else {
                if (!sha_eq(a->sha1, o->sha1) && !sha_eq(b->sha1, o->sha1))
@@ -710,9 +648,9 @@ static struct merge_file_info merge_file(struct diff_filespec *o,
                result.mode = a->mode == o->mode ? b->mode: a->mode;
 
                if (sha_eq(a->sha1, o->sha1))
-                       memcpy(result.sha, b->sha1, 20);
+                       hashcpy(result.sha, b->sha1);
                else if (sha_eq(b->sha1, o->sha1))
-                       memcpy(result.sha, a->sha1, 20);
+                       hashcpy(result.sha, a->sha1);
                else if (S_ISREG(a->mode)) {
                        int code = 1, fd;
                        struct stat st;
@@ -721,7 +659,7 @@ static struct merge_file_info merge_file(struct diff_filespec *o,
                        char src2[PATH_MAX];
                        const char *argv[] = {
                                "merge", "-L", NULL, "-L", NULL, "-L", NULL,
-                               src1, orig, src2,
+                               NULL, NULL, NULL,
                                NULL
                        };
                        char *la, *lb, *lo;
@@ -730,15 +668,13 @@ static struct merge_file_info merge_file(struct diff_filespec *o,
                        git_unpack_file(a->sha1, src1);
                        git_unpack_file(b->sha1, src2);
 
-                       argv[2] = la = strdup(mkpath("%s/%s", branch1Name, a->path));
-                       argv[6] = lb = strdup(mkpath("%s/%s", branch2Name, b->path));
-                       argv[4] = lo = strdup(mkpath("orig/%s", o->path));
+                       argv[2] = la = xstrdup(mkpath("%s/%s", branch1, a->path));
+                       argv[6] = lb = xstrdup(mkpath("%s/%s", branch2, b->path));
+                       argv[4] = lo = xstrdup(mkpath("orig/%s", o->path));
+                       argv[7] = src1;
+                       argv[8] = orig;
+                       argv[9] = src2,
 
-#if 0
-                       printf("%s %s %s %s %s %s %s %s %s %s\n",
-                              argv[0], argv[1], argv[2], argv[3], argv[4],
-                              argv[5], argv[6], argv[7], argv[8], argv[9]);
-#endif
                        code = run_command_v(10, argv);
 
                        free(la);
@@ -763,7 +699,7 @@ static struct merge_file_info merge_file(struct diff_filespec *o,
                        if (!(S_ISLNK(a->mode) || S_ISLNK(b->mode)))
                                die("cannot merge modes?");
 
-                       memcpy(result.sha, a->sha1, 20);
+                       hashcpy(result.sha, a->sha1);
 
                        if (!sha_eq(a->sha1, b->sha1))
                                result.clean = 0;
@@ -829,7 +765,6 @@ static void conflict_rename_rename_2(struct rename *ren1,
        free(new_path1);
 }
 
-/* General TODO: get rid of all the debug messages */
 static int process_renames(struct path_list *a_renames,
                           struct path_list *b_renames,
                           const char *a_branch,
@@ -867,8 +802,10 @@ static int process_renames(struct path_list *a_renames,
                } else {
                        compare = strcmp(a_renames->items[i].path,
                                        b_renames->items[j].path);
-                       ren1 = a_renames->items[i++].util;
-                       ren2 = b_renames->items[j++].util;
+                       if (compare <= 0)
+                               ren1 = a_renames->items[i++].util;
+                       if (compare >= 0)
+                               ren2 = b_renames->items[j++].util;
                }
 
                /* TODO: refactor, so that 1/2 are not needed */
@@ -954,11 +891,9 @@ static int process_renames(struct path_list *a_renames,
 
                        remove_file(1, ren1_src);
 
-                       memcpy(src_other.sha1,
-                                       ren1->src_entry->stages[stage].sha, 20);
+                       hashcpy(src_other.sha1, ren1->src_entry->stages[stage].sha);
                        src_other.mode = ren1->src_entry->stages[stage].mode;
-                       memcpy(dst_other.sha1,
-                                       ren1->dst_entry->stages[stage].sha, 20);
+                       hashcpy(dst_other.sha1, ren1->dst_entry->stages[stage].sha);
                        dst_other.mode = ren1->dst_entry->stages[stage].mode;
 
                        try_merge = 0;
@@ -1043,13 +978,13 @@ static int process_renames(struct path_list *a_renames,
 
 static unsigned char *has_sha(const unsigned char *sha)
 {
-       return memcmp(sha, null_sha1, 20) == 0 ? NULL: (unsigned char *)sha;
+       return is_null_sha1(sha) ? NULL: (unsigned char *)sha;
 }
 
 /* Per entry merge function */
 static int process_entry(const char *path, struct stage_data *entry,
-                        const char *branch1Name,
-                        const char *branch2Name)
+                        const char *branch1,
+                        const char *branch2)
 {
        /*
        printf("processing entry, clean cache: %s\n", index_only ? "yes": "no");
@@ -1079,14 +1014,14 @@ static int process_entry(const char *path, struct stage_data *entry,
                        if (!a_sha) {
                                output("CONFLICT (delete/modify): %s deleted in %s "
                                       "and modified in %s. Version %s of %s left in tree.",
-                                      path, branch1Name,
-                                      branch2Name, branch2Name, path);
+                                      path, branch1,
+                                      branch2, branch2, path);
                                update_file(0, b_sha, b_mode, path);
                        } else {
                                output("CONFLICT (delete/modify): %s deleted in %s "
                                       "and modified in %s. Version %s of %s left in tree.",
-                                      path, branch2Name,
-                                      branch1Name, branch1Name, path);
+                                      path, branch2,
+                                      branch1, branch1, path);
                                update_file(0, a_sha, a_mode, path);
                        }
                }
@@ -1101,14 +1036,14 @@ static int process_entry(const char *path, struct stage_data *entry,
                const char *conf;
 
                if (a_sha) {
-                       add_branch = branch1Name;
-                       other_branch = branch2Name;
+                       add_branch = branch1;
+                       other_branch = branch2;
                        mode = a_mode;
                        sha = a_sha;
                        conf = "file/directory";
                } else {
-                       add_branch = branch2Name;
-                       other_branch = branch1Name;
+                       add_branch = branch2;
+                       other_branch = branch1;
                        mode = b_mode;
                        sha = b_sha;
                        conf = "directory/file";
@@ -1142,8 +1077,8 @@ static int process_entry(const char *path, struct stage_data *entry,
                } else {
                        const char *new_path1, *new_path2;
                        clean_merge = 0;
-                       new_path1 = unique_path(path, branch1Name);
-                       new_path2 = unique_path(path, branch2Name);
+                       new_path1 = unique_path(path, branch1);
+                       new_path2 = unique_path(path, branch2);
                        output("CONFLICT (add/add): File %s added non-identically "
                               "in both branches. Adding as %s and %s instead.",
                               path, new_path1, new_path2);
@@ -1159,15 +1094,15 @@ static int process_entry(const char *path, struct stage_data *entry,
 
                output("Auto-merging %s", path);
                o.path = a.path = b.path = (char *)path;
-               memcpy(o.sha1, o_sha, 20);
+               hashcpy(o.sha1, o_sha);
                o.mode = o_mode;
-               memcpy(a.sha1, a_sha, 20);
+               hashcpy(a.sha1, a_sha);
                a.mode = a_mode;
-               memcpy(b.sha1, b_sha, 20);
+               hashcpy(b.sha1, b_sha);
                b.mode = b_mode;
 
                mfi = merge_file(&o, &a, &b,
-                                branch1Name, branch2Name);
+                                branch1, branch2);
 
                if (mfi.clean)
                        update_file(1, mfi.sha, mfi.mode, path);
@@ -1193,8 +1128,8 @@ static int process_entry(const char *path, struct stage_data *entry,
 static int merge_trees(struct tree *head,
                       struct tree *merge,
                       struct tree *common,
-                      const char *branch1Name,
-                      const char *branch2Name,
+                      const char *branch1,
+                      const char *branch2,
                       struct tree **result)
 {
        int code, clean;
@@ -1204,7 +1139,7 @@ static int merge_trees(struct tree *head,
                return 1;
        }
 
-       code = git_merge_trees(index_only ? "-i": "-u", common, head, merge);
+       code = git_merge_trees(index_only, common, head, merge);
 
        if (code != 0)
                die("merging of trees %s and %s failed",
@@ -1225,13 +1160,13 @@ static int merge_trees(struct tree *head,
                re_head  = get_renames(head, common, head, merge, entries);
                re_merge = get_renames(merge, common, head, merge, entries);
                clean = process_renames(re_head, re_merge,
-                               branch1Name, branch2Name);
+                               branch1, branch2);
                for (i = 0; i < entries->nr; i++) {
                        const char *path = entries->items[i].path;
                        struct stage_data *e = entries->items[i].util;
                        if (e->processed)
                                continue;
-                       if (!process_entry(path, e, branch1Name, branch2Name))
+                       if (!process_entry(path, e, branch1, branch2))
                                clean = 0;
                }
 
@@ -1254,6 +1189,17 @@ static int merge_trees(struct tree *head,
        return clean;
 }
 
+static struct commit_list *reverse_commit_list(struct commit_list *list)
+{
+       struct commit_list *next = NULL, *current, *backup;
+       for (current = list; current; current = backup) {
+               backup = current->next;
+               current->next = next;
+               next = current;
+       }
+       return next;
+}
+
 /*
  * Merge the commits h1 and h2, return the resulting virtual
  * commit object and a flag indicating the cleaness of the merge.
@@ -1261,8 +1207,8 @@ static int merge_trees(struct tree *head,
 static
 int merge(struct commit *h1,
                          struct commit *h2,
-                         const char *branch1Name,
-                         const char *branch2Name,
+                         const char *branch1,
+                         const char *branch2,
                          int call_depth /* =0 */,
                          struct commit *ancestor /* =None */,
                          struct commit **result)
@@ -1279,13 +1225,22 @@ int merge(struct commit *h1,
        if (ancestor)
                commit_list_insert(ancestor, &ca);
        else
-               ca = get_merge_bases(h1, h2, 1);
+               ca = reverse_commit_list(get_merge_bases(h1, h2, 1));
 
        output("found %u common ancestor(s):", commit_list_count(ca));
        for (iter = ca; iter; iter = iter->next)
                output_commit_title(iter->item);
 
        merged_common_ancestors = pop_commit(&ca);
+       if (merged_common_ancestors == NULL) {
+               /* if there is no common ancestor, make an empty tree */
+               struct tree *tree = xcalloc(1, sizeof(struct tree));
+
+               tree->object.parsed = 1;
+               tree->object.type = OBJ_TREE;
+               hash_sha1_file(NULL, 0, tree_type, tree->object.sha1);
+               merged_common_ancestors = make_virtual_commit(tree, "ancestor");
+       }
 
        for (iter = ca; iter; iter = iter->next) {
                output_indent = call_depth + 1;
@@ -1318,7 +1273,7 @@ int merge(struct commit *h1,
        }
 
        clean = merge_trees(h1->tree, h2->tree, merged_common_ancestors->tree,
-                           branch1Name, branch2Name, &mrtree);
+                           branch1, branch2, &mrtree);
 
        if (!ancestor && (clean || index_only)) {
                *result = make_virtual_commit(mrtree, "merged tree");
@@ -1356,9 +1311,9 @@ int main(int argc, char *argv[])
        original_index_file = getenv("GIT_INDEX_FILE");
 
        if (!original_index_file)
-               original_index_file = strdup(git_path("index"));
+               original_index_file = xstrdup(git_path("index"));
 
-       temporary_index_file = strdup(git_path("mrg-rcrsv-tmp-idx"));
+       temporary_index_file = xstrdup(git_path("mrg-rcrsv-tmp-idx"));
 
        if (argc < 4)
                die("Usage: %s <base>... -- <head> <remote> ...\n", argv[0]);