gitweb: Change header search action to use parse_commits.
[gitweb.git] / merge-recursive.c
index 6a796f24c7f3cdba2c6c2dc1c93bdfcd0c5c2ea1..ca4f19e34d4216fed7c8110ba8f75585c69f92c7 100644 (file)
@@ -3,13 +3,6 @@
  * Fredrik Kuivinen.
  * The thieves were Alex Riesen and Johannes Schindelin, in June/July 2006
  */
-#include <stdarg.h>
-#include <string.h>
-#include <assert.h>
-#include <sys/wait.h>
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <time.h>
 #include "cache.h"
 #include "cache-tree.h"
 #include "commit.h"
@@ -19,8 +12,9 @@
 #include "diffcore.h"
 #include "run-command.h"
 #include "tag.h"
-
+#include "unpack-trees.h"
 #include "path-list.h"
+#include "xdiff-interface.h"
 
 /*
  * A virtual commit has
@@ -43,6 +37,8 @@ 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;
 }
 
@@ -54,7 +50,7 @@ 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;
 }
 
 /*
@@ -96,7 +92,7 @@ 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 {
@@ -114,6 +110,7 @@ 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;
@@ -122,12 +119,10 @@ 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;
@@ -135,11 +130,12 @@ 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();
 }
 
@@ -156,7 +152,7 @@ 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);
@@ -172,7 +168,7 @@ 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)
@@ -191,69 +187,89 @@ 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)
 {
        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)
 {
        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)
 {
-       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,
@@ -261,7 +277,7 @@ 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';
@@ -316,7 +332,7 @@ 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++) {
@@ -333,7 +349,7 @@ 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;
@@ -405,8 +421,9 @@ static struct path_list *get_renames(struct tree *tree,
        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)
@@ -433,7 +450,7 @@ 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, '/'))) {
@@ -446,24 +463,19 @@ 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)
+static int remove_file(int clean, const char *path, int no_wd)
 {
        int update_cache = index_only || clean;
-       int update_working_directory = !index_only;
+       int update_working_directory = !index_only && !no_wd;
 
        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 (update_working_directory)
-       {
+       if (update_working_directory) {
                unlink(path);
                if (errno != ENOENT || errno != EISDIR)
                        return -1;
@@ -477,9 +489,9 @@ 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)
@@ -495,8 +507,8 @@ 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;
@@ -519,11 +531,11 @@ 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;
@@ -554,7 +566,7 @@ 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);
@@ -568,10 +580,10 @@ 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);
 }
@@ -586,24 +598,21 @@ struct merge_file_info
                 merge:1;
 };
 
-static char *git_unpack_file(const unsigned char *sha1, char *path)
+static void fill_mm(const unsigned char *sha1, mmfile_t *mm)
 {
-       void *buf;
-       char type[20];
        unsigned long size;
-       int fd;
+       char type[20];
 
-       buf = read_sha1_file(sha1, type, &size);
-       if (!buf || strcmp(type, blob_type))
-               die("unable to read blob object %s", sha1_to_hex(sha1));
+       if (!hashcmp(sha1, null_sha1)) {
+               mm->ptr = xstrdup("");
+               mm->size = 0;
+               return;
+       }
 
-       strcpy(path, ".merge_file_XXXXXX");
-       fd = mkstemp(path);
-       if (fd < 0)
-               die("unable to create temp-file");
-       flush_buffer(fd, buf, size);
-       close(fd);
-       return path;
+       mm->ptr = read_sha1_file(sha1, type, &size);
+       if (!mm->ptr || strcmp(type, blob_type))
+               die("unable to read blob object %s", sha1_to_hex(sha1));
+       mm->size = size;
 }
 
 static struct merge_file_info merge_file(struct diff_filespec *o,
@@ -618,10 +627,10 @@ 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))
@@ -630,58 +639,50 @@ 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;
-                       char orig[PATH_MAX];
-                       char src1[PATH_MAX];
-                       char src2[PATH_MAX];
-                       const char *argv[] = {
-                               "merge", "-L", NULL, "-L", NULL, "-L", NULL,
-                               NULL, NULL, NULL,
-                               NULL
-                       };
-                       char *la, *lb, *lo;
-
-                       git_unpack_file(o->sha1, orig);
-                       git_unpack_file(a->sha1, src1);
-                       git_unpack_file(b->sha1, src2);
-
-                       argv[2] = la = strdup(mkpath("%s/%s", branch1, a->path));
-                       argv[6] = lb = strdup(mkpath("%s/%s", branch2, b->path));
-                       argv[4] = lo = strdup(mkpath("orig/%s", o->path));
-                       argv[7] = src1;
-                       argv[8] = orig;
-                       argv[9] = src2,
-
-                       code = run_command_v(10, argv);
-
-                       free(la);
-                       free(lb);
-                       free(lo);
-                       if (code && code < -256) {
-                               die("Failed to execute 'merge'. merge(1) is used as the "
-                                   "file-level merge tool. Is 'merge' in your path?");
-                       }
-                       fd = open(src1, O_RDONLY);
-                       if (fd < 0 || fstat(fd, &st) < 0 ||
-                                       index_fd(result.sha, fd, &st, 1,
-                                               "blob"))
-                               die("Unable to add %s to database", src1);
-
-                       unlink(orig);
-                       unlink(src1);
-                       unlink(src2);
-
-                       result.clean = WEXITSTATUS(code) == 0;
+                       mmfile_t orig, src1, src2;
+                       mmbuffer_t result_buf;
+                       xpparam_t xpp;
+                       char *name1, *name2;
+                       int merge_status;
+
+                       name1 = xstrdup(mkpath("%s:%s", branch1, a->path));
+                       name2 = xstrdup(mkpath("%s:%s", branch2, b->path));
+
+                       fill_mm(o->sha1, &orig);
+                       fill_mm(a->sha1, &src1);
+                       fill_mm(b->sha1, &src2);
+
+                       memset(&xpp, 0, sizeof(xpp));
+                       merge_status = xdl_merge(&orig,
+                                                &src1, name1,
+                                                &src2, name2,
+                                                &xpp, XDL_MERGE_ZEALOUS,
+                                                &result_buf);
+                       free(name1);
+                       free(name2);
+                       free(orig.ptr);
+                       free(src1.ptr);
+                       free(src2.ptr);
+
+                       if ((merge_status < 0) || !result_buf.ptr)
+                               die("Failed to execute internal merge");
+
+                       if (write_sha1_file(result_buf.ptr, result_buf.size,
+                                           blob_type, result.sha))
+                               die("Unable to add %s to database",
+                                   a->path);
+
+                       free(result_buf.ptr);
+                       result.clean = (merge_status == 0);
                } else {
                        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;
@@ -706,13 +707,13 @@ static void conflict_rename_rename(struct rename *ren1,
                dst_name1 = del[delp++] = unique_path(ren1_dst, branch1);
                output("%s is a directory in %s adding as %s instead",
                       ren1_dst, branch2, dst_name1);
-               remove_file(0, ren1_dst);
+               remove_file(0, ren1_dst, 0);
        }
        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, dst_name2);
-               remove_file(0, ren2_dst);
+               remove_file(0, ren2_dst, 0);
        }
        update_stages(dst_name1, NULL, ren1->pair->two, NULL, 1);
        update_stages(dst_name2, NULL, NULL, ren2->pair->two, 1);
@@ -725,7 +726,7 @@ static void conflict_rename_dir(struct rename *ren1,
 {
        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);
+       remove_file(0, ren1->pair->two->path, 0);
        update_file(0, ren1->pair->two->sha1, ren1->pair->two->mode, new_path);
        free(new_path);
 }
@@ -740,7 +741,7 @@ static void conflict_rename_rename_2(struct rename *ren1,
        output("Renaming %s to %s and %s to %s instead",
               ren1->pair->one->path, new_path1,
               ren2->pair->one->path, new_path2);
-       remove_file(0, ren1->pair->two->path);
+       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);
@@ -784,8 +785,10 @@ 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 */
@@ -836,7 +839,7 @@ static int process_renames(struct path_list *a_renames,
                                conflict_rename_rename(ren1, branch1, ren2, branch2);
                        } else {
                                struct merge_file_info mfi;
-                               remove_file(1, ren1_src);
+                               remove_file(1, ren1_src, 1);
                                mfi = merge_file(ren1->pair->one,
                                                 ren1->pair->two,
                                                 ren2->pair->two,
@@ -869,13 +872,11 @@ static int process_renames(struct path_list *a_renames,
                        struct diff_filespec src_other, dst_other;
                        int try_merge, stage = a_renames == renames1 ? 3: 2;
 
-                       remove_file(1, ren1_src);
+                       remove_file(1, ren1_src, index_only);
 
-                       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;
@@ -960,7 +961,7 @@ 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 */
@@ -989,7 +990,8 @@ static int process_entry(const char *path, struct stage_data *entry,
                         * unchanged in the other */
                        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 */
                        clean_merge = 0;
@@ -1036,51 +1038,30 @@ static int process_entry(const char *path, struct stage_data *entry,
                        output("CONFLICT (%s): There is a directory with name %s in %s. "
                               "Adding %s as %s",
                               conf, path, other_branch, path, new_path);
-                       remove_file(0, 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 (!o_sha && a_sha && b_sha) {
-               /* Case C: Added in both (check for same permissions). */
-               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, 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 *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, new_path1, new_path2);
-                       remove_file(0, path);
-                       update_file(0, a_sha, a_mode, new_path1);
-                       update_file(0, b_sha, b_mode, new_path2);
-               }
-
-       } else if (o_sha && a_sha && b_sha) {
+       } else if (a_sha && b_sha) {
+               /* Case C: Added in both (check for same permissions) and */
                /* case D: Modified in both, but differently. */
+               const char *reason = "content";
                struct merge_file_info mfi;
                struct diff_filespec o, a, b;
 
+               if (!o_sha) {
+                       reason = "add/add";
+                       o_sha = (unsigned char *)null_sha1;
+               }
                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,
@@ -1090,7 +1071,8 @@ static int process_entry(const char *path, struct stage_data *entry,
                        update_file(1, mfi.sha, mfi.mode, path);
                else {
                        clean_merge = 0;
-                       output("CONFLICT (content): Merge conflict in %s", path);
+                       output("CONFLICT (%s): Merge conflict in %s",
+                                       reason, path);
 
                        if (index_only)
                                update_file(0, mfi.sha, mfi.mode, path);
@@ -1121,7 +1103,7 @@ 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",
@@ -1171,18 +1153,28 @@ 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 *branch1,
-                         const char *branch2,
-                         int call_depth /* =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 *merged_common_ancestors;
@@ -1196,13 +1188,22 @@ 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;
+               write_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;
@@ -1262,6 +1263,18 @@ static struct commit *get_ref(const char *ref)
        return (struct commit *)object;
 }
 
+static const char *better_branch_name(const char *branch)
+{
+       static char githead_env[8 + 40 + 1];
+       char *name;
+
+       if (strlen(branch) != 40)
+               return branch;
+       sprintf(githead_env, "GITHEAD_%s", branch);
+       name = getenv(githead_env);
+       return name ? name : branch;
+}
+
 int main(int argc, char *argv[])
 {
        static const char *bases[2];
@@ -1270,12 +1283,13 @@ int main(int argc, char *argv[])
        const char *branch1, *branch2;
        struct commit *result, *h1, *h2;
 
-       original_index_file = getenv("GIT_INDEX_FILE");
+       git_config(git_default_config); /* core.filemode */
+       original_index_file = getenv(INDEX_ENVIRONMENT);
 
        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]);
@@ -1291,11 +1305,14 @@ int main(int argc, char *argv[])
 
        branch1 = argv[++i];
        branch2 = argv[++i];
-       printf("Merging %s with %s\n", branch1, branch2);
 
        h1 = get_ref(branch1);
        h2 = get_ref(branch2);
 
+       branch1 = better_branch_name(branch1);
+       branch2 = better_branch_name(branch2);
+       printf("Merging %s with %s\n", branch1, branch2);
+
        if (bases_count == 1) {
                struct commit *ancestor = get_ref(bases[0]);
                clean = merge(h1, h2, branch1, branch2, 0, ancestor, &result);