git-svn: allow SVN:: lib users to track the root of the repository (again)
[gitweb.git] / merge-recursive.c
index d78f58d8d2463c49bf14d3639ec60772b232f7f9..cd2cc77bf47025a9dfc88f594961521c3ec8f22c 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
 {
@@ -122,8 +73,8 @@ struct stage_data
        unsigned processed:1;
 };
 
-static struct path_list currentFileSet = {NULL, 0, 0, 1};
-static struct path_list currentDirectorySet = {NULL, 0, 0, 1};
+static struct path_list current_file_set = {NULL, 0, 0, 1};
+static struct path_list current_directory_set = {NULL, 0, 0, 1};
 
 static int output_indent = 0;
 
@@ -147,7 +98,7 @@ static void output_commit_title(struct commit *commit)
        if (commit->util)
                printf("virtual %s\n", (char *)commit->util);
        else {
-               printf("%s ", sha1_to_hex(commit->object.sha1));
+               printf("%s ", find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
                if (parse_commit(commit) != 0)
                        printf("(bad commit)\n");
                else {
@@ -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,
@@ -329,15 +283,15 @@ 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';
 
        if (S_ISDIR(mode))
-               path_list_insert(newpath, &currentDirectorySet);
+               path_list_insert(newpath, &current_directory_set);
        else
-               path_list_insert(newpath, &currentFileSet);
+               path_list_insert(newpath, &current_file_set);
        free(newpath);
 
        return READ_TREE_RECURSIVE;
@@ -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 = currentFileSet.nr + currentDirectorySet.nr;
-       debug("  get_files_dirs done (%d)\n", n);
+       n = current_file_set.nr + current_directory_set.nr;
        return n;
 }
 
@@ -378,7 +328,7 @@ static struct stage_data *insert_stage_data(const char *path,
 }
 
 /*
- * Create a dictionary mapping file names to CacheEntry objects. The
+ * Create a dictionary mapping file names to stage_data objects. The
  * dictionary contains one entry for every path with a non-zero stage entry.
  */
 static struct path_list *get_unmerged(void)
@@ -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;
@@ -420,25 +370,20 @@ struct rename
 };
 
 /*
- * Get information of all renames which occured between 'oTree' and
- * 'tree'. We need the three trees in the merge ('oTree', 'aTree' and
- * 'bTree') to be able to associate the correct cache entries with
- * the rename information. 'tree' is always equal to either aTree or bTree.
+ * Get information of all renames which occured between 'o_tree' and
+ * 'tree'. We need the three trees in the merge ('o_tree', 'a_tree' and
+ * 'b_tree') to be able to associate the correct cache entries with
+ * the rename information. 'tree' is always equal to either a_tree or b_tree.
  */
 static struct path_list *get_renames(struct tree *tree,
-                                       struct tree *oTree,
-                                       struct tree *aTree,
-                                       struct tree *bTree,
+                                       struct tree *o_tree,
+                                       struct tree *a_tree,
+                                       struct tree *b_tree,
                                        struct path_list *entries)
 {
        int i;
        struct path_list *renames;
        struct diff_options opts;
-#ifdef DEBUG
-       time_t t = time(0);
-
-       debug("getRenames ...\n");
-#endif
 
        renames = xcalloc(1, sizeof(struct path_list));
        diff_setup(&opts);
@@ -447,7 +392,7 @@ static struct path_list *get_renames(struct tree *tree,
        opts.output_format = DIFF_FORMAT_NO_OUTPUT;
        if (diff_setup_done(&opts) < 0)
                die("diff setup failed");
-       diff_tree_sha1(oTree->object.sha1, tree->object.sha1, "", &opts);
+       diff_tree_sha1(o_tree->object.sha1, tree->object.sha1, "", &opts);
        diffcore_std(&opts);
        for (i = 0; i < diff_queued_diff.nr; ++i) {
                struct path_list_item *item;
@@ -463,14 +408,14 @@ static struct path_list *get_renames(struct tree *tree,
                item = path_list_lookup(re->pair->one->path, entries);
                if (!item)
                        re->src_entry = insert_stage_data(re->pair->one->path,
-                                       oTree, aTree, bTree, entries);
+                                       o_tree, a_tree, b_tree, entries);
                else
                        re->src_entry = item->util;
 
                item = path_list_lookup(re->pair->two->path, entries);
                if (!item)
                        re->dst_entry = insert_stage_data(re->pair->two->path,
-                                       oTree, aTree, bTree, entries);
+                                       o_tree, a_tree, b_tree, entries);
                else
                        re->dst_entry = item->util;
                item = path_list_insert(pair->one->path, renames);
@@ -479,14 +424,12 @@ 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("  getRenames done in %ld\n", time(0)-t);
-#endif
        return renames;
 }
 
-int update_stages(const char *path, struct diff_filespec *o,
-               struct diff_filespec *a, struct diff_filespec *b, int clear)
+static int update_stages(const char *path, struct diff_filespec *o,
+                        struct diff_filespec *a, struct diff_filespec *b,
+                        int clear)
 {
        int options = ADD_CACHE_OK_TO_ADD | ADD_CACHE_OK_TO_REPLACE;
        if (clear)
@@ -513,7 +456,7 @@ 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, '/'))) {
@@ -526,26 +469,19 @@ static int remove_path(const char *name)
        return ret;
 }
 
-/* General TODO: unC99ify the code: no declaration after code */
-/* General TODO: no javaIfiCation: rename updateCache to update_cache */
-/*
- * 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)
+static int remove_file(int clean, const char *path, int no_wd)
 {
-       int updateCache = index_only || clean;
-       int updateWd = !index_only;
+       int update_cache = index_only || clean;
+       int update_working_directory = !index_only && !no_wd;
 
-       if (updateCache) {
+       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;
        }
-       if (updateWd)
-       {
+       if (update_working_directory) {
                unlink(path);
                if (errno != ENOENT || errno != EISDIR)
                        return -1;
@@ -559,26 +495,26 @@ 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)
                        *p = '_';
-       while (path_list_has_path(&currentFileSet, newpath) ||
-              path_list_has_path(&currentDirectorySet, newpath) ||
+       while (path_list_has_path(&current_file_set, newpath) ||
+              path_list_has_path(&current_directory_set, newpath) ||
               lstat(newpath, &st) == 0)
                sprintf(p, "_%d", suffix++);
 
-       path_list_insert(newpath, &currentFileSet);
+       path_list_insert(newpath, &current_file_set);
        return newpath;
 }
 
 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;
@@ -601,11 +537,11 @@ static void flush_buffer(int fd, const char *buf, unsigned long size)
        }
 }
 
-void update_file_flags(const unsigned char *sha,
-                      unsigned mode,
-                      const char *path,
-                      int update_cache,
-                      int update_wd)
+static void update_file_flags(const unsigned char *sha,
+                             unsigned mode,
+                             const char *path,
+                             int update_cache,
+                             int update_wd)
 {
        if (index_only)
                update_wd = 0;
@@ -636,7 +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);
@@ -650,10 +586,10 @@ void update_file_flags(const unsigned char *sha,
                add_cacheinfo(mode, sha, path, 0, update_wd, ADD_CACHE_OK_TO_ADD);
 }
 
-void update_file(int clean,
-               const unsigned char *sha,
-               unsigned mode,
-               const char *path)
+static void update_file(int clean,
+                       const unsigned char *sha,
+                       unsigned mode,
+                       const char *path)
 {
        update_file_flags(sha, mode, path, index_only || clean, !index_only);
 }
@@ -690,7 +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;
@@ -700,10 +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))
@@ -712,9 +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;
@@ -723,7 +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;
@@ -732,15 +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);
@@ -765,7 +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;
@@ -784,22 +718,22 @@ static void conflict_rename_rename(struct rename *ren1,
        int delp = 0;
        const char *ren1_dst = ren1->pair->two->path;
        const char *ren2_dst = ren2->pair->two->path;
-       const char *dstName1 = ren1_dst;
-       const char *dstName2 = ren2_dst;
-       if (path_list_has_path(&currentDirectorySet, ren1_dst)) {
-               dstName1 = del[delp++] = unique_path(ren1_dst, branch1);
+       const char *dst_name1 = ren1_dst;
+       const char *dst_name2 = ren2_dst;
+       if (path_list_has_path(&current_directory_set, ren1_dst)) {
+               dst_name1 = del[delp++] = unique_path(ren1_dst, branch1);
                output("%s is a directory in %s adding as %s instead",
-                      ren1_dst, branch2, dstName1);
-               remove_file(0, ren1_dst);
+                      ren1_dst, branch2, dst_name1);
+               remove_file(0, ren1_dst, 0);
        }
-       if (path_list_has_path(&currentDirectorySet, ren2_dst)) {
-               dstName2 = del[delp++] = unique_path(ren2_dst, branch2);
+       if (path_list_has_path(&current_directory_set, ren2_dst)) {
+               dst_name2 = del[delp++] = unique_path(ren2_dst, branch2);
                output("%s is a directory in %s adding as %s instead",
-                      ren2_dst, branch1, dstName2);
-               remove_file(0, ren2_dst);
+                      ren2_dst, branch1, dst_name2);
+               remove_file(0, ren2_dst, 0);
        }
-       update_stages(dstName1, NULL, ren1->pair->two, NULL, 1);
-       update_stages(dstName2, NULL, NULL, ren2->pair->two, 1);
+       update_stages(dst_name1, NULL, ren1->pair->two, NULL, 1);
+       update_stages(dst_name2, NULL, NULL, ren2->pair->two, 1);
        while (delp--)
                free(del[delp]);
 }
@@ -807,11 +741,11 @@ static void conflict_rename_rename(struct rename *ren1,
 static void conflict_rename_dir(struct rename *ren1,
                                const char *branch1)
 {
-       char *newPath = unique_path(ren1->pair->two->path, branch1);
-       output("Renaming %s to %s instead", ren1->pair->one->path, newPath);
-       remove_file(0, ren1->pair->two->path);
-       update_file(0, ren1->pair->two->sha1, ren1->pair->two->mode, newPath);
-       free(newPath);
+       char *new_path = unique_path(ren1->pair->two->path, branch1);
+       output("Renaming %s to %s instead", ren1->pair->one->path, new_path);
+       remove_file(0, ren1->pair->two->path, 0);
+       update_file(0, ren1->pair->two->sha1, ren1->pair->two->mode, new_path);
+       free(new_path);
 }
 
 static void conflict_rename_rename_2(struct rename *ren1,
@@ -819,74 +753,75 @@ static void conflict_rename_rename_2(struct rename *ren1,
                                     struct rename *ren2,
                                     const char *branch2)
 {
-       char *newPath1 = unique_path(ren1->pair->two->path, branch1);
-       char *newPath2 = unique_path(ren2->pair->two->path, branch2);
+       char *new_path1 = unique_path(ren1->pair->two->path, branch1);
+       char *new_path2 = unique_path(ren2->pair->two->path, branch2);
        output("Renaming %s to %s and %s to %s instead",
-              ren1->pair->one->path, newPath1,
-              ren2->pair->one->path, newPath2);
-       remove_file(0, ren1->pair->two->path);
-       update_file(0, ren1->pair->two->sha1, ren1->pair->two->mode, newPath1);
-       update_file(0, ren2->pair->two->sha1, ren2->pair->two->mode, newPath2);
-       free(newPath2);
-       free(newPath1);
+              ren1->pair->one->path, new_path1,
+              ren2->pair->one->path, new_path2);
+       remove_file(0, ren1->pair->two->path, 0);
+       update_file(0, ren1->pair->two->sha1, ren1->pair->two->mode, new_path1);
+       update_file(0, ren2->pair->two->sha1, ren2->pair->two->mode, new_path2);
+       free(new_path2);
+       free(new_path1);
 }
 
-/* General TODO: get rid of all the debug messages */
-static int process_renames(struct path_list *renamesA,
-                          struct path_list *renamesB,
-                          const char *branchNameA,
-                          const char *branchNameB)
+static int process_renames(struct path_list *a_renames,
+                          struct path_list *b_renames,
+                          const char *a_branch,
+                          const char *b_branch)
 {
-       int cleanMerge = 1, i, j;
-       struct path_list byDstA = {NULL, 0, 0, 0}, byDstB = {NULL, 0, 0, 0};
+       int clean_merge = 1, i, j;
+       struct path_list a_by_dst = {NULL, 0, 0, 0}, b_by_dst = {NULL, 0, 0, 0};
        const struct rename *sre;
 
-       for (i = 0; i < renamesA->nr; i++) {
-               sre = renamesA->items[i].util;
-               path_list_insert(sre->pair->two->path, &byDstA)->util
+       for (i = 0; i < a_renames->nr; i++) {
+               sre = a_renames->items[i].util;
+               path_list_insert(sre->pair->two->path, &a_by_dst)->util
                        = sre->dst_entry;
        }
-       for (i = 0; i < renamesB->nr; i++) {
-               sre = renamesB->items[i].util;
-               path_list_insert(sre->pair->two->path, &byDstB)->util
+       for (i = 0; i < b_renames->nr; i++) {
+               sre = b_renames->items[i].util;
+               path_list_insert(sre->pair->two->path, &b_by_dst)->util
                        = sre->dst_entry;
        }
 
-       for (i = 0, j = 0; i < renamesA->nr || j < renamesB->nr;) {
+       for (i = 0, j = 0; i < a_renames->nr || j < b_renames->nr;) {
                int compare;
                char *src;
                struct path_list *renames1, *renames2, *renames2Dst;
                struct rename *ren1 = NULL, *ren2 = NULL;
-               const char *branchName1, *branchName2;
+               const char *branch1, *branch2;
                const char *ren1_src, *ren1_dst;
 
-               if (i >= renamesA->nr) {
+               if (i >= a_renames->nr) {
                        compare = 1;
-                       ren2 = renamesB->items[j++].util;
-               } else if (j >= renamesB->nr) {
+                       ren2 = b_renames->items[j++].util;
+               } else if (j >= b_renames->nr) {
                        compare = -1;
-                       ren1 = renamesA->items[i++].util;
+                       ren1 = a_renames->items[i++].util;
                } else {
-                       compare = strcmp(renamesA->items[i].path,
-                                       renamesB->items[j].path);
-                       ren1 = renamesA->items[i++].util;
-                       ren2 = renamesB->items[j++].util;
+                       compare = strcmp(a_renames->items[i].path,
+                                       b_renames->items[j].path);
+                       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 */
                if (ren1) {
-                       renames1 = renamesA;
-                       renames2 = renamesB;
-                       renames2Dst = &byDstB;
-                       branchName1 = branchNameA;
-                       branchName2 = branchNameB;
+                       renames1 = a_renames;
+                       renames2 = b_renames;
+                       renames2Dst = &b_by_dst;
+                       branch1 = a_branch;
+                       branch2 = b_branch;
                } else {
                        struct rename *tmp;
-                       renames1 = renamesB;
-                       renames2 = renamesA;
-                       renames2Dst = &byDstA;
-                       branchName1 = branchNameB;
-                       branchName2 = branchNameA;
+                       renames1 = b_renames;
+                       renames2 = a_renames;
+                       renames2Dst = &a_by_dst;
+                       branch1 = b_branch;
+                       branch2 = a_branch;
                        tmp = ren2;
                        ren2 = ren1;
                        ren1 = tmp;
@@ -912,21 +847,21 @@ static int process_renames(struct path_list *renamesA,
                        ren2->dst_entry->processed = 1;
                        ren2->processed = 1;
                        if (strcmp(ren1_dst, ren2_dst) != 0) {
-                               cleanMerge = 0;
+                               clean_merge = 0;
                                output("CONFLICT (rename/rename): "
                                       "Rename %s->%s in branch %s "
                                       "rename %s->%s in %s",
-                                      src, ren1_dst, branchName1,
-                                      src, ren2_dst, branchName2);
-                               conflict_rename_rename(ren1, branchName1, ren2, branchName2);
+                                      src, ren1_dst, branch1,
+                                      src, ren2_dst, branch2);
+                               conflict_rename_rename(ren1, branch1, ren2, branch2);
                        } else {
-                               remove_file(1, ren1_src);
                                struct merge_file_info mfi;
+                               remove_file(1, ren1_src, 1);
                                mfi = merge_file(ren1->pair->one,
                                                 ren1->pair->two,
                                                 ren2->pair->two,
-                                                branchName1,
-                                                branchName2);
+                                                branch1,
+                                                branch2);
                                if (mfi.merge || !mfi.clean)
                                        output("Renaming %s->%s", src, ren1_dst);
 
@@ -936,7 +871,7 @@ static int process_renames(struct path_list *renamesA,
                                if (!mfi.clean) {
                                        output("CONFLICT (content): merge conflict in %s",
                                               ren1_dst);
-                                       cleanMerge = 0;
+                                       clean_merge = 0;
 
                                        if (!index_only)
                                                update_stages(ren1_dst,
@@ -952,63 +887,61 @@ static int process_renames(struct path_list *renamesA,
                        struct path_list_item *item;
                        /* we only use sha1 and mode of these */
                        struct diff_filespec src_other, dst_other;
-                       int tryMerge, stage = renamesA == renames1 ? 3: 2;
+                       int try_merge, stage = a_renames == renames1 ? 3: 2;
 
-                       remove_file(1, ren1_src);
+                       remove_file(1, ren1_src, 1);
 
-                       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;
 
-                       tryMerge = 0;
+                       try_merge = 0;
 
-                       if (path_list_has_path(&currentDirectorySet, ren1_dst)) {
-                               cleanMerge = 0;
+                       if (path_list_has_path(&current_directory_set, ren1_dst)) {
+                               clean_merge = 0;
                                output("CONFLICT (rename/directory): Rename %s->%s in %s "
                                       " directory %s added in %s",
-                                      ren1_src, ren1_dst, branchName1,
-                                      ren1_dst, branchName2);
-                               conflict_rename_dir(ren1, branchName1);
+                                      ren1_src, ren1_dst, branch1,
+                                      ren1_dst, branch2);
+                               conflict_rename_dir(ren1, branch1);
                        } else if (sha_eq(src_other.sha1, null_sha1)) {
-                               cleanMerge = 0;
+                               clean_merge = 0;
                                output("CONFLICT (rename/delete): Rename %s->%s in %s "
                                       "and deleted in %s",
-                                      ren1_src, ren1_dst, branchName1,
-                                      branchName2);
+                                      ren1_src, ren1_dst, branch1,
+                                      branch2);
                                update_file(0, ren1->pair->two->sha1, ren1->pair->two->mode, ren1_dst);
                        } else if (!sha_eq(dst_other.sha1, null_sha1)) {
-                               const char *newPath;
-                               cleanMerge = 0;
-                               tryMerge = 1;
+                               const char *new_path;
+                               clean_merge = 0;
+                               try_merge = 1;
                                output("CONFLICT (rename/add): Rename %s->%s in %s. "
                                       "%s added in %s",
-                                      ren1_src, ren1_dst, branchName1,
-                                      ren1_dst, branchName2);
-                               newPath = unique_path(ren1_dst, branchName2);
-                               output("Adding as %s instead", newPath);
-                               update_file(0, dst_other.sha1, dst_other.mode, newPath);
+                                      ren1_src, ren1_dst, branch1,
+                                      ren1_dst, branch2);
+                               new_path = unique_path(ren1_dst, branch2);
+                               output("Adding as %s instead", new_path);
+                               update_file(0, dst_other.sha1, dst_other.mode, new_path);
                        } else if ((item = path_list_lookup(ren1_dst, renames2Dst))) {
                                ren2 = item->util;
-                               cleanMerge = 0;
+                               clean_merge = 0;
                                ren2->processed = 1;
                                output("CONFLICT (rename/rename): Rename %s->%s in %s. "
                                       "Rename %s->%s in %s",
-                                      ren1_src, ren1_dst, branchName1,
-                                      ren2->pair->one->path, ren2->pair->two->path, branchName2);
-                               conflict_rename_rename_2(ren1, branchName1, ren2, branchName2);
+                                      ren1_src, ren1_dst, branch1,
+                                      ren2->pair->one->path, ren2->pair->two->path, branch2);
+                               conflict_rename_rename_2(ren1, branch1, ren2, branch2);
                        } else
-                               tryMerge = 1;
+                               try_merge = 1;
 
-                       if (tryMerge) {
+                       if (try_merge) {
                                struct diff_filespec *o, *a, *b;
                                struct merge_file_info mfi;
                                src_other.path = (char *)ren1_src;
 
                                o = ren1->pair->one;
-                               if (renamesA == renames1) {
+                               if (a_renames == renames1) {
                                        a = ren1->pair->two;
                                        b = &src_other;
                                } else {
@@ -1016,7 +949,7 @@ static int process_renames(struct path_list *renamesA,
                                        a = &src_other;
                                }
                                mfi = merge_file(o, a, b,
-                                               branchNameA, branchNameB);
+                                               a_branch, b_branch);
 
                                if (mfi.merge || !mfi.clean)
                                        output("Renaming %s => %s", ren1_src, ren1_dst);
@@ -1025,7 +958,7 @@ static int process_renames(struct path_list *renamesA,
                                if (!mfi.clean) {
                                        output("CONFLICT (rename/modify): Merge conflict in %s",
                                               ren1_dst);
-                                       cleanMerge = 0;
+                                       clean_merge = 0;
 
                                        if (!index_only)
                                                update_stages(ren1_dst,
@@ -1035,153 +968,154 @@ static int process_renames(struct path_list *renamesA,
                        }
                }
        }
-       path_list_clear(&byDstA, 0);
-       path_list_clear(&byDstB, 0);
+       path_list_clear(&a_by_dst, 0);
+       path_list_clear(&b_by_dst, 0);
 
        if (cache_dirty)
                flush_cache();
-       return cleanMerge;
+       return clean_merge;
 }
 
 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");
        print_index_entry("\tpath: ", entry);
        */
-       int cleanMerge = 1;
-       unsigned char *oSha = has_sha(entry->stages[1].sha);
-       unsigned char *aSha = has_sha(entry->stages[2].sha);
-       unsigned char *bSha = has_sha(entry->stages[3].sha);
-       unsigned oMode = entry->stages[1].mode;
-       unsigned aMode = entry->stages[2].mode;
-       unsigned bMode = entry->stages[3].mode;
-
-       if (oSha && (!aSha || !bSha)) {
+       int clean_merge = 1;
+       unsigned char *o_sha = has_sha(entry->stages[1].sha);
+       unsigned char *a_sha = has_sha(entry->stages[2].sha);
+       unsigned char *b_sha = has_sha(entry->stages[3].sha);
+       unsigned o_mode = entry->stages[1].mode;
+       unsigned a_mode = entry->stages[2].mode;
+       unsigned b_mode = entry->stages[3].mode;
+
+       if (o_sha && (!a_sha || !b_sha)) {
                /* Case A: Deleted in one */
-               if ((!aSha && !bSha) ||
-                   (sha_eq(aSha, oSha) && !bSha) ||
-                   (!aSha && sha_eq(bSha, oSha))) {
+               if ((!a_sha && !b_sha) ||
+                   (sha_eq(a_sha, o_sha) && !b_sha) ||
+                   (!a_sha && sha_eq(b_sha, o_sha))) {
                        /* Deleted in both or deleted in one and
                         * unchanged in the other */
-                       if (aSha)
+                       if (a_sha)
                                output("Removing %s", path);
-                       remove_file(1, path);
+                       /* do not touch working file if it did not exist */
+                       remove_file(1, path, !a_sha);
                } else {
                        /* Deleted in one and changed in the other */
-                       cleanMerge = 0;
-                       if (!aSha) {
+                       clean_merge = 0;
+                       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);
-                               update_file(0, bSha, bMode, 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);
-                               update_file(0, aSha, aMode, path);
+                                      path, branch2,
+                                      branch1, branch1, path);
+                               update_file(0, a_sha, a_mode, path);
                        }
                }
 
-       } else if ((!oSha && aSha && !bSha) ||
-                  (!oSha && !aSha && bSha)) {
+       } else if ((!o_sha && a_sha && !b_sha) ||
+                  (!o_sha && !a_sha && b_sha)) {
                /* Case B: Added in one. */
-               const char *addBranch;
-               const char *otherBranch;
+               const char *add_branch;
+               const char *other_branch;
                unsigned mode;
                const unsigned char *sha;
                const char *conf;
 
-               if (aSha) {
-                       addBranch = branch1Name;
-                       otherBranch = branch2Name;
-                       mode = aMode;
-                       sha = aSha;
+               if (a_sha) {
+                       add_branch = branch1;
+                       other_branch = branch2;
+                       mode = a_mode;
+                       sha = a_sha;
                        conf = "file/directory";
                } else {
-                       addBranch = branch2Name;
-                       otherBranch = branch1Name;
-                       mode = bMode;
-                       sha = bSha;
+                       add_branch = branch2;
+                       other_branch = branch1;
+                       mode = b_mode;
+                       sha = b_sha;
                        conf = "directory/file";
                }
-               if (path_list_has_path(&currentDirectorySet, path)) {
-                       const char *newPath = unique_path(path, addBranch);
-                       cleanMerge = 0;
+               if (path_list_has_path(&current_directory_set, path)) {
+                       const char *new_path = unique_path(path, add_branch);
+                       clean_merge = 0;
                        output("CONFLICT (%s): There is a directory with name %s in %s. "
                               "Adding %s as %s",
-                              conf, path, otherBranch, path, newPath);
-                       remove_file(0, path);
-                       update_file(0, sha, mode, newPath);
+                              conf, path, other_branch, path, new_path);
+                       remove_file(0, path, 0);
+                       update_file(0, sha, mode, new_path);
                } else {
                        output("Adding %s", path);
                        update_file(1, sha, mode, path);
                }
-       } else if (!oSha && aSha && bSha) {
+       } else if (!o_sha && a_sha && b_sha) {
                /* Case C: Added in both (check for same permissions). */
-               if (sha_eq(aSha, bSha)) {
-                       if (aMode != bMode) {
-                               cleanMerge = 0;
+               if (sha_eq(a_sha, b_sha)) {
+                       if (a_mode != b_mode) {
+                               clean_merge = 0;
                                output("CONFLICT: File %s added identically in both branches, "
                                       "but permissions conflict %06o->%06o",
-                                      path, aMode, bMode);
-                               output("CONFLICT: adding with permission: %06o", aMode);
-                               update_file(0, aSha, aMode, path);
+                                      path, a_mode, b_mode);
+                               output("CONFLICT: adding with permission: %06o", a_mode);
+                               update_file(0, a_sha, a_mode, path);
                        } else {
                                /* This case is handled by git-read-tree */
                                assert(0 && "This case must be handled by git-read-tree");
                        }
                } else {
-                       const char *newPath1, *newPath2;
-                       cleanMerge = 0;
-                       newPath1 = unique_path(path, branch1Name);
-                       newPath2 = unique_path(path, branch2Name);
+                       const char *new_path1, *new_path2;
+                       clean_merge = 0;
+                       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, newPath1, newPath2);
-                       remove_file(0, path);
-                       update_file(0, aSha, aMode, newPath1);
-                       update_file(0, bSha, bMode, newPath2);
+                              path, new_path1, new_path2);
+                       remove_file(0, path, 0);
+                       update_file(0, a_sha, a_mode, new_path1);
+                       update_file(0, b_sha, b_mode, new_path2);
                }
 
-       } else if (oSha && aSha && bSha) {
+       } else if (o_sha && a_sha && b_sha) {
                /* case D: Modified in both, but differently. */
                struct merge_file_info mfi;
                struct diff_filespec o, a, b;
 
                output("Auto-merging %s", path);
                o.path = a.path = b.path = (char *)path;
-               memcpy(o.sha1, oSha, 20);
-               o.mode = oMode;
-               memcpy(a.sha1, aSha, 20);
-               a.mode = aMode;
-               memcpy(b.sha1, bSha, 20);
-               b.mode = bMode;
+               hashcpy(o.sha1, o_sha);
+               o.mode = o_mode;
+               hashcpy(a.sha1, a_sha);
+               a.mode = a_mode;
+               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);
                else {
-                       cleanMerge = 0;
+                       clean_merge = 0;
                        output("CONFLICT (content): Merge conflict in %s", path);
 
                        if (index_only)
                                update_file(0, mfi.sha, mfi.mode, path);
                        else
                                update_file_flags(mfi.sha, mfi.mode, path,
-                                             0 /* updateCache */, 1 /* updateWd */);
+                                             0 /* update_cache */, 1 /* update_working_directory */);
                }
        } else
                die("Fatal merge failure, shouldn't happen.");
@@ -1189,14 +1123,14 @@ static int process_entry(const char *path, struct stage_data *entry,
        if (cache_dirty)
                flush_cache();
 
-       return cleanMerge;
+       return clean_merge;
 }
 
 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;
@@ -1206,7 +1140,7 @@ 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",
@@ -1218,8 +1152,8 @@ static int merge_trees(struct tree *head,
        if (!*result) {
                struct path_list *entries, *re_head, *re_merge;
                int i;
-               path_list_clear(&currentFileSet, 1);
-               path_list_clear(&currentDirectorySet, 1);
+               path_list_clear(&current_file_set, 1);
+               path_list_clear(&current_directory_set, 1);
                get_files_dirs(head);
                get_files_dirs(merge);
 
@@ -1227,13 +1161,13 @@ 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;
                }
 
@@ -1256,21 +1190,31 @@ 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.
  */
-static
-int merge(struct commit *h1,
-                         struct commit *h2,
-                         const char *branch1Name,
-                         const char *branch2Name,
-                         int callDepth /* =0 */,
-                         struct commit *ancestor /* =None */,
-                         struct commit **result)
+static int merge(struct commit *h1,
+                struct commit *h2,
+                const char *branch1,
+                const char *branch2,
+                int call_depth /* =0 */,
+                struct commit *ancestor /* =None */,
+                struct commit **result)
 {
        struct commit_list *ca = NULL, *iter;
-       struct commit *mergedCA;
+       struct commit *merged_common_ancestors;
        struct tree *mrtree;
        int clean;
 
@@ -1281,16 +1225,25 @@ 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);
 
-       mergedCA = pop_commit(&ca);
+       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 = callDepth + 1;
+               output_indent = call_depth + 1;
                /*
                 * When the merge fails, the result contains files
                 * with conflict markers. The cleanness flag is
@@ -1298,19 +1251,19 @@ int merge(struct commit *h1,
                 * merge_trees has always overwritten it: the commited
                 * "conflicts" were already resolved.
                 */
-               merge(mergedCA, iter->item,
+               merge(merged_common_ancestors, iter->item,
                      "Temporary merge branch 1",
                      "Temporary merge branch 2",
-                     callDepth + 1,
+                     call_depth + 1,
                      NULL,
-                     &mergedCA);
-               output_indent = callDepth;
+                     &merged_common_ancestors);
+               output_indent = call_depth;
 
-               if (!mergedCA)
+               if (!merged_common_ancestors)
                        die("merge returned no commit");
        }
 
-       if (callDepth == 0) {
+       if (call_depth == 0) {
                setup_index(0 /* $GIT_DIR/index */);
                index_only = 0;
        } else {
@@ -1319,8 +1272,8 @@ int merge(struct commit *h1,
                index_only = 1;
        }
 
-       clean = merge_trees(h1->tree, h2->tree, mergedCA->tree,
-                           branch1Name, branch2Name, &mrtree);
+       clean = merge_trees(h1->tree, h2->tree, merged_common_ancestors->tree,
+                           branch1, branch2, &mrtree);
 
        if (!ancestor && (clean || index_only)) {
                *result = make_virtual_commit(mrtree, "merged tree");
@@ -1355,12 +1308,13 @@ int main(int argc, char *argv[])
        const char *branch1, *branch2;
        struct commit *result, *h1, *h2;
 
+       git_config(git_default_config); /* core.filemode */
        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]);