diff: allow turning on textconv explicitly for plumbing
[gitweb.git] / merge-recursive.c
index 6c6f595fbc7da09a41228e09cd2c5ef48b91f3f0..a0c804c8171d021780680f11901680d4c7e89e0b 100644 (file)
@@ -7,18 +7,18 @@
 #include "cache-tree.h"
 #include "commit.h"
 #include "blob.h"
+#include "builtin.h"
 #include "tree-walk.h"
 #include "diff.h"
 #include "diffcore.h"
-#include "run-command.h"
 #include "tag.h"
 #include "unpack-trees.h"
-#include "path-list.h"
+#include "string-list.h"
 #include "xdiff-interface.h"
-#include "interpolate.h"
+#include "ll-merge.h"
 #include "attr.h"
-
-static int subtree_merge;
+#include "merge-recursive.h"
+#include "dir.h"
 
 static struct tree *shift_tree_object(struct tree *one, struct tree *two)
 {
@@ -35,26 +35,14 @@ static struct tree *shift_tree_object(struct tree *one, struct tree *two)
 }
 
 /*
- * A virtual commit has
- * - (const char *)commit->util set to the name, and
- * - *(int *)commit->object.sha1 set to the virtual id.
+ * A virtual commit has (const char *)commit->util set to the name.
  */
 
-static unsigned commit_list_count(const struct commit_list *l)
-{
-       unsigned c = 0;
-       for (; l; l = l->next )
-               c++;
-       return c;
-}
-
-static struct commit *make_virtual_commit(struct tree *tree, const char *comment)
+struct commit *make_virtual_commit(struct tree *tree, const char *comment)
 {
        struct commit *commit = xcalloc(1, sizeof(struct commit));
-       static unsigned virtual_id = 1;
        commit->tree = tree;
        commit->util = (void*)comment;
-       *(int*)commit->object.sha1 = virtual_id++;
        /* avoid warnings */
        commit->object.parsed = 1;
        return commit;
@@ -85,66 +73,57 @@ struct stage_data
        unsigned processed: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 call_depth = 0;
-static int verbosity = 2;
-static int rename_limit = -1;
-static int buffer_output = 1;
-static struct strbuf obuf = STRBUF_INIT;
-
-static int show(int v)
+static int show(struct merge_options *o, int v)
 {
-       return (!call_depth && verbosity >= v) || verbosity >= 5;
+       return (!o->call_depth && o->verbosity >= v) || o->verbosity >= 5;
 }
 
-static void flush_output(void)
+static void flush_output(struct merge_options *o)
 {
-       if (obuf.len) {
-               fputs(obuf.buf, stdout);
-               strbuf_reset(&obuf);
+       if (o->obuf.len) {
+               fputs(o->obuf.buf, stdout);
+               strbuf_reset(&o->obuf);
        }
 }
 
-static void output(int v, const char *fmt, ...)
+static void output(struct merge_options *o, int v, const char *fmt, ...)
 {
        int len;
        va_list ap;
 
-       if (!show(v))
+       if (!show(o, v))
                return;
 
-       strbuf_grow(&obuf, call_depth * 2 + 2);
-       memset(obuf.buf + obuf.len, ' ', call_depth * 2);
-       strbuf_setlen(&obuf, obuf.len + call_depth * 2);
+       strbuf_grow(&o->obuf, o->call_depth * 2 + 2);
+       memset(o->obuf.buf + o->obuf.len, ' ', o->call_depth * 2);
+       strbuf_setlen(&o->obuf, o->obuf.len + o->call_depth * 2);
 
        va_start(ap, fmt);
-       len = vsnprintf(obuf.buf + obuf.len, strbuf_avail(&obuf), fmt, ap);
+       len = vsnprintf(o->obuf.buf + o->obuf.len, strbuf_avail(&o->obuf), fmt, ap);
        va_end(ap);
 
        if (len < 0)
                len = 0;
-       if (len >= strbuf_avail(&obuf)) {
-               strbuf_grow(&obuf, len + 2);
+       if (len >= strbuf_avail(&o->obuf)) {
+               strbuf_grow(&o->obuf, len + 2);
                va_start(ap, fmt);
-               len = vsnprintf(obuf.buf + obuf.len, strbuf_avail(&obuf), fmt, ap);
+               len = vsnprintf(o->obuf.buf + o->obuf.len, strbuf_avail(&o->obuf), fmt, ap);
                va_end(ap);
-               if (len >= strbuf_avail(&obuf)) {
+               if (len >= strbuf_avail(&o->obuf)) {
                        die("this should not happen, your snprintf is broken");
                }
        }
-       strbuf_setlen(&obuf, obuf.len + len);
-       strbuf_add(&obuf, "\n", 1);
-       if (!buffer_output)
-               flush_output();
+       strbuf_setlen(&o->obuf, o->obuf.len + len);
+       strbuf_add(&o->obuf, "\n", 1);
+       if (!o->buffer_output)
+               flush_output(o);
 }
 
-static void output_commit_title(struct commit *commit)
+static void output_commit_title(struct merge_options *o, struct commit *commit)
 {
        int i;
-       flush_output();
-       for (i = call_depth; i--;)
+       flush_output(o);
+       for (i = o->call_depth; i--;)
                fputs("  ", stdout);
        if (commit->util)
                printf("virtual %s\n", (char *)commit->util);
@@ -177,17 +156,6 @@ static int add_cacheinfo(unsigned int mode, const unsigned char *sha1,
        return add_cache_entry(ce, options);
 }
 
-/*
- * This is a global variable which is used in a number of places but
- * only written to in the 'merge' function.
- *
- * index_only == 1    => Don't leave any non-stage 0 entries in the cache and
- *                       don't update the working directory.
- *               0    => Leave unmerged entries in the cache and update
- *                       the working directory.
- */
-static int index_only = 0;
-
 static void init_tree_desc_from_tree(struct tree_desc *desc, struct tree *tree)
 {
        parse_tree(tree);
@@ -211,6 +179,8 @@ static int git_merge_trees(int index_only,
        opts.merge = 1;
        opts.head_idx = 2;
        opts.fn = threeway_merge;
+       opts.src_index = &the_index;
+       opts.dst_index = &the_index;
 
        init_tree_desc_from_tree(t+0, common);
        init_tree_desc_from_tree(t+1, head);
@@ -221,28 +191,17 @@ static int git_merge_trees(int index_only,
        return rc;
 }
 
-static int unmerged_index(void)
-{
-       int i;
-       for (i = 0; i < active_nr; i++) {
-               struct cache_entry *ce = active_cache[i];
-               if (ce_stage(ce))
-                       return 1;
-       }
-       return 0;
-}
-
-static struct tree *git_write_tree(void)
+struct tree *write_tree_from_memory(struct merge_options *o)
 {
        struct tree *result = NULL;
 
-       if (unmerged_index()) {
+       if (unmerged_cache()) {
                int i;
-               output(0, "There are unmerged index entries:");
+               output(o, 0, "There are unmerged index entries:");
                for (i = 0; i < active_nr; i++) {
                        struct cache_entry *ce = active_cache[i];
                        if (ce_stage(ce))
-                               output(0, "%d %.*s", ce_stage(ce), ce_namelen(ce), ce->name);
+                               output(o, 0, "%d %.*s", ce_stage(ce), ce_namelen(ce), ce->name);
                }
                return NULL;
        }
@@ -262,41 +221,43 @@ static struct tree *git_write_tree(void)
 
 static int save_files_dirs(const unsigned char *sha1,
                const char *base, int baselen, const char *path,
-               unsigned int mode, int stage)
+               unsigned int mode, int stage, void *context)
 {
        int len = strlen(path);
        char *newpath = xmalloc(baselen + len + 1);
+       struct merge_options *o = context;
+
        memcpy(newpath, base, baselen);
        memcpy(newpath + baselen, path, len);
        newpath[baselen + len] = '\0';
 
        if (S_ISDIR(mode))
-               path_list_insert(newpath, &current_directory_set);
+               string_list_insert(newpath, &o->current_directory_set);
        else
-               path_list_insert(newpath, &current_file_set);
+               string_list_insert(newpath, &o->current_file_set);
        free(newpath);
 
        return READ_TREE_RECURSIVE;
 }
 
-static int get_files_dirs(struct tree *tree)
+static int get_files_dirs(struct merge_options *o, struct tree *tree)
 {
        int n;
-       if (read_tree_recursive(tree, "", 0, 0, NULL, save_files_dirs) != 0)
+       if (read_tree_recursive(tree, "", 0, 0, NULL, save_files_dirs, o))
                return 0;
-       n = current_file_set.nr + current_directory_set.nr;
+       n = o->current_file_set.nr + o->current_directory_set.nr;
        return n;
 }
 
 /*
- * Returns a index_entry instance which doesn't have to correspond to
+ * Returns an index_entry instance which doesn't have to correspond to
  * a real cache entry in Git's index.
  */
 static struct stage_data *insert_stage_data(const char *path,
                struct tree *o, struct tree *a, struct tree *b,
-               struct path_list *entries)
+               struct string_list *entries)
 {
-       struct path_list_item *item;
+       struct string_list_item *item;
        struct stage_data *e = xcalloc(1, sizeof(struct stage_data));
        get_tree_entry(o->object.sha1, path,
                        e->stages[1].sha, &e->stages[1].mode);
@@ -304,7 +265,7 @@ static struct stage_data *insert_stage_data(const char *path,
                        e->stages[2].sha, &e->stages[2].mode);
        get_tree_entry(b->object.sha1, path,
                        e->stages[3].sha, &e->stages[3].mode);
-       item = path_list_insert(path, entries);
+       item = string_list_insert(path, entries);
        item->util = e;
        return e;
 }
@@ -313,27 +274,27 @@ static struct stage_data *insert_stage_data(const char *path,
  * 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)
+static struct string_list *get_unmerged(void)
 {
-       struct path_list *unmerged = xcalloc(1, sizeof(struct path_list));
+       struct string_list *unmerged = xcalloc(1, sizeof(struct string_list));
        int i;
 
-       unmerged->strdup_paths = 1;
+       unmerged->strdup_strings = 1;
 
        for (i = 0; i < active_nr; i++) {
-               struct path_list_item *item;
+               struct string_list_item *item;
                struct stage_data *e;
                struct cache_entry *ce = active_cache[i];
                if (!ce_stage(ce))
                        continue;
 
-               item = path_list_lookup(ce->name, unmerged);
+               item = string_list_lookup(ce->name, unmerged);
                if (!item) {
-                       item = path_list_insert(ce->name, unmerged);
+                       item = string_list_insert(ce->name, unmerged);
                        item->util = xcalloc(1, sizeof(struct stage_data));
                }
                e = item->util;
-               e->stages[ce_stage(ce)].mode = ntohl(ce->ce_mode);
+               e->stages[ce_stage(ce)].mode = ce->ce_mode;
                hashcpy(e->stages[ce_stage(ce)].sha, ce->sha1);
        }
 
@@ -354,28 +315,32 @@ struct rename
  * '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 *o_tree,
-                                       struct tree *a_tree,
-                                       struct tree *b_tree,
-                                       struct path_list *entries)
+static struct string_list *get_renames(struct merge_options *o,
+                                      struct tree *tree,
+                                      struct tree *o_tree,
+                                      struct tree *a_tree,
+                                      struct tree *b_tree,
+                                      struct string_list *entries)
 {
        int i;
-       struct path_list *renames;
+       struct string_list *renames;
        struct diff_options opts;
 
-       renames = xcalloc(1, sizeof(struct path_list));
+       renames = xcalloc(1, sizeof(struct string_list));
        diff_setup(&opts);
-       opts.recursive = 1;
+       DIFF_OPT_SET(&opts, RECURSIVE);
        opts.detect_rename = DIFF_DETECT_RENAME;
-       opts.rename_limit = rename_limit;
+       opts.rename_limit = o->merge_rename_limit >= 0 ? o->merge_rename_limit :
+                           o->diff_rename_limit >= 0 ? o->diff_rename_limit :
+                           500;
+       opts.warn_on_too_large_rename = 1;
        opts.output_format = DIFF_FORMAT_NO_OUTPUT;
        if (diff_setup_done(&opts) < 0)
                die("diff setup failed");
        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;
+               struct string_list_item *item;
                struct rename *re;
                struct diff_filepair *pair = diff_queued_diff.queue[i];
                if (pair->status != 'R') {
@@ -385,20 +350,20 @@ static struct path_list *get_renames(struct tree *tree,
                re = xmalloc(sizeof(*re));
                re->processed = 0;
                re->pair = pair;
-               item = path_list_lookup(re->pair->one->path, entries);
+               item = string_list_lookup(re->pair->one->path, entries);
                if (!item)
                        re->src_entry = insert_stage_data(re->pair->one->path,
                                        o_tree, a_tree, b_tree, entries);
                else
                        re->src_entry = item->util;
 
-               item = path_list_lookup(re->pair->two->path, entries);
+               item = string_list_lookup(re->pair->two->path, entries);
                if (!item)
                        re->dst_entry = insert_stage_data(re->pair->two->path,
                                        o_tree, a_tree, b_tree, entries);
                else
                        re->dst_entry = item->util;
-               item = path_list_insert(pair->one->path, renames);
+               item = string_list_insert(pair->one->path, renames);
                item->util = re;
        }
        opts.output_format = DIFF_FORMAT_NO_OUTPUT;
@@ -427,43 +392,24 @@ static int update_stages(const char *path, struct diff_filespec *o,
        return 0;
 }
 
-static int remove_path(const char *name)
+static int remove_file(struct merge_options *o, int clean,
+                      const char *path, int no_wd)
 {
-       int ret;
-       char *slash, *dirs;
-
-       ret = unlink(name);
-       if (ret)
-               return ret;
-       dirs = xstrdup(name);
-       while ((slash = strrchr(name, '/'))) {
-               *slash = '\0';
-               if (rmdir(name) != 0)
-                       break;
-       }
-       free(dirs);
-       return ret;
-}
-
-static int remove_file(int clean, const char *path, int no_wd)
-{
-       int update_cache = index_only || clean;
-       int update_working_directory = !index_only && !no_wd;
+       int update_cache = o->call_depth || clean;
+       int update_working_directory = !o->call_depth && !no_wd;
 
        if (update_cache) {
                if (remove_file_from_cache(path))
                        return -1;
        }
        if (update_working_directory) {
-               unlink(path);
-               if (errno != ENOENT || errno != EISDIR)
+               if (remove_path(path) && errno != ENOENT)
                        return -1;
-               remove_path(path);
        }
        return 0;
 }
 
-static char *unique_path(const char *path, const char *branch)
+static char *unique_path(struct merge_options *o, const char *path, const char *branch)
 {
        char *newpath = xmalloc(strlen(path) + 1 + strlen(branch) + 8 + 1);
        int suffix = 0;
@@ -475,24 +421,15 @@ static char *unique_path(const char *path, const char *branch)
        for (; *p; ++p)
                if ('/' == *p)
                        *p = '_';
-       while (path_list_has_path(&current_file_set, newpath) ||
-              path_list_has_path(&current_directory_set, newpath) ||
+       while (string_list_has_string(&o->current_file_set, newpath) ||
+              string_list_has_string(&o->current_directory_set, newpath) ||
               lstat(newpath, &st) == 0)
                sprintf(p, "_%d", suffix++);
 
-       path_list_insert(newpath, &current_file_set);
+       string_list_insert(newpath, &o->current_file_set);
        return newpath;
 }
 
-static int mkdir_p(const char *path, unsigned long mode)
-{
-       /* 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;
-}
-
 static void flush_buffer(int fd, const char *buf, unsigned long size)
 {
        while (size > 0) {
@@ -515,7 +452,7 @@ static int make_room_for_path(const char *path)
        int status;
        const char *msg = "failed to create path '%s'%s";
 
-       status = mkdir_p(path, 0777);
+       status = safe_create_leading_directories_const(path);
        if (status) {
                if (status == -3) {
                        /* something else exists */
@@ -535,13 +472,14 @@ static int make_room_for_path(const char *path)
        return error(msg, path, ": perhaps a D/F conflict?");
 }
 
-static void update_file_flags(const unsigned char *sha,
+static void update_file_flags(struct merge_options *o,
+                             const unsigned char *sha,
                              unsigned mode,
                              const char *path,
                              int update_cache,
                              int update_wd)
 {
-       if (index_only)
+       if (o->call_depth)
                update_wd = 0;
 
        if (update_wd) {
@@ -549,14 +487,27 @@ static void update_file_flags(const unsigned char *sha,
                void *buf;
                unsigned long size;
 
+               if (S_ISGITLINK(mode))
+                       die("cannot read object %s '%s': It is a submodule!",
+                           sha1_to_hex(sha), path);
+
                buf = read_sha1_file(sha, &type, &size);
                if (!buf)
                        die("cannot read object %s '%s'", sha1_to_hex(sha), path);
                if (type != OBJ_BLOB)
                        die("blob expected for %s '%s'", sha1_to_hex(sha), path);
+               if (S_ISREG(mode)) {
+                       struct strbuf strbuf = STRBUF_INIT;
+                       if (convert_to_working_tree(path, buf, size, &strbuf)) {
+                               free(buf);
+                               size = strbuf.len;
+                               buf = strbuf_detach(&strbuf, NULL);
+                       }
+               }
 
                if (make_room_for_path(path) < 0) {
                        update_wd = 0;
+                       free(buf);
                        goto update_index;
                }
                if (S_ISREG(mode) || (!has_symlinks && S_ISLNK(mode))) {
@@ -572,25 +523,28 @@ static void update_file_flags(const unsigned char *sha,
                        close(fd);
                } else if (S_ISLNK(mode)) {
                        char *lnk = xmemdupz(buf, size);
-                       mkdir_p(path, 0777);
+                       safe_create_leading_directories_const(path);
                        unlink(path);
-                       symlink(lnk, path);
+                       if (symlink(lnk, path))
+                               die("failed to symlink %s: %s", path, strerror(errno));
                        free(lnk);
                } else
                        die("do not know what to do with %06o %s '%s'",
                            mode, sha1_to_hex(sha), path);
+               free(buf);
        }
  update_index:
        if (update_cache)
                add_cacheinfo(mode, sha, path, 0, update_wd, ADD_CACHE_OK_TO_ADD);
 }
 
-static void update_file(int clean,
+static void update_file(struct merge_options *o,
+                       int clean,
                        const unsigned char *sha,
                        unsigned mode,
                        const char *path)
 {
-       update_file_flags(sha, mode, path, index_only || clean, !index_only);
+       update_file_flags(o, sha, mode, path, o->call_depth || clean, !o->call_depth);
 }
 
 /* Low level file merging, update and removal */
@@ -620,379 +574,28 @@ static void fill_mm(const unsigned char *sha1, mmfile_t *mm)
        mm->size = size;
 }
 
-/*
- * Customizable low-level merge drivers support.
- */
-
-struct ll_merge_driver;
-typedef int (*ll_merge_fn)(const struct ll_merge_driver *,
-                          const char *path,
-                          mmfile_t *orig,
-                          mmfile_t *src1, const char *name1,
-                          mmfile_t *src2, const char *name2,
-                          mmbuffer_t *result);
-
-struct ll_merge_driver {
-       const char *name;
-       const char *description;
-       ll_merge_fn fn;
-       const char *recursive;
-       struct ll_merge_driver *next;
-       char *cmdline;
-};
-
-/*
- * Built-in low-levels
- */
-static int ll_binary_merge(const struct ll_merge_driver *drv_unused,
-                          const char *path_unused,
-                          mmfile_t *orig,
-                          mmfile_t *src1, const char *name1,
-                          mmfile_t *src2, const char *name2,
-                          mmbuffer_t *result)
-{
-       /*
-        * The tentative merge result is "ours" for the final round,
-        * or common ancestor for an internal merge.  Still return
-        * "conflicted merge" status.
-        */
-       mmfile_t *stolen = index_only ? orig : src1;
-
-       result->ptr = stolen->ptr;
-       result->size = stolen->size;
-       stolen->ptr = NULL;
-       return 1;
-}
-
-static int ll_xdl_merge(const struct ll_merge_driver *drv_unused,
-                       const char *path_unused,
-                       mmfile_t *orig,
-                       mmfile_t *src1, const char *name1,
-                       mmfile_t *src2, const char *name2,
-                       mmbuffer_t *result)
-{
-       xpparam_t xpp;
-
-       if (buffer_is_binary(orig->ptr, orig->size) ||
-           buffer_is_binary(src1->ptr, src1->size) ||
-           buffer_is_binary(src2->ptr, src2->size)) {
-               warning("Cannot merge binary files: %s vs. %s\n",
-                       name1, name2);
-               return ll_binary_merge(drv_unused, path_unused,
-                                      orig, src1, name1,
-                                      src2, name2,
-                                      result);
-       }
-
-       memset(&xpp, 0, sizeof(xpp));
-       return xdl_merge(orig,
-                        src1, name1,
-                        src2, name2,
-                        &xpp, XDL_MERGE_ZEALOUS,
-                        result);
-}
-
-static int ll_union_merge(const struct ll_merge_driver *drv_unused,
-                         const char *path_unused,
-                         mmfile_t *orig,
-                         mmfile_t *src1, const char *name1,
-                         mmfile_t *src2, const char *name2,
-                         mmbuffer_t *result)
-{
-       char *src, *dst;
-       long size;
-       const int marker_size = 7;
-
-       int status = ll_xdl_merge(drv_unused, path_unused,
-                                 orig, src1, NULL, src2, NULL, result);
-       if (status <= 0)
-               return status;
-       size = result->size;
-       src = dst = result->ptr;
-       while (size) {
-               char ch;
-               if ((marker_size < size) &&
-                   (*src == '<' || *src == '=' || *src == '>')) {
-                       int i;
-                       ch = *src;
-                       for (i = 0; i < marker_size; i++)
-                               if (src[i] != ch)
-                                       goto not_a_marker;
-                       if (src[marker_size] != '\n')
-                               goto not_a_marker;
-                       src += marker_size + 1;
-                       size -= marker_size + 1;
-                       continue;
-               }
-       not_a_marker:
-               do {
-                       ch = *src++;
-                       *dst++ = ch;
-                       size--;
-               } while (ch != '\n' && size);
-       }
-       result->size = dst - result->ptr;
-       return 0;
-}
-
-#define LL_BINARY_MERGE 0
-#define LL_TEXT_MERGE 1
-#define LL_UNION_MERGE 2
-static struct ll_merge_driver ll_merge_drv[] = {
-       { "binary", "built-in binary merge", ll_binary_merge },
-       { "text", "built-in 3-way text merge", ll_xdl_merge },
-       { "union", "built-in union merge", ll_union_merge },
-};
-
-static void create_temp(mmfile_t *src, char *path)
-{
-       int fd;
-
-       strcpy(path, ".merge_file_XXXXXX");
-       fd = xmkstemp(path);
-       if (write_in_full(fd, src->ptr, src->size) != src->size)
-               die("unable to write temp-file");
-       close(fd);
-}
-
-/*
- * User defined low-level merge driver support.
- */
-static int ll_ext_merge(const struct ll_merge_driver *fn,
-                       const char *path,
-                       mmfile_t *orig,
-                       mmfile_t *src1, const char *name1,
-                       mmfile_t *src2, const char *name2,
-                       mmbuffer_t *result)
-{
-       char temp[3][50];
-       char cmdbuf[2048];
-       struct interp table[] = {
-               { "%O" },
-               { "%A" },
-               { "%B" },
-       };
-       struct child_process child;
-       const char *args[20];
-       int status, fd, i;
-       struct stat st;
-
-       if (fn->cmdline == NULL)
-               die("custom merge driver %s lacks command line.", fn->name);
-
-       result->ptr = NULL;
-       result->size = 0;
-       create_temp(orig, temp[0]);
-       create_temp(src1, temp[1]);
-       create_temp(src2, temp[2]);
-
-       interp_set_entry(table, 0, temp[0]);
-       interp_set_entry(table, 1, temp[1]);
-       interp_set_entry(table, 2, temp[2]);
-
-       output(1, "merging %s using %s", path,
-              fn->description ? fn->description : fn->name);
-
-       interpolate(cmdbuf, sizeof(cmdbuf), fn->cmdline, table, 3);
-
-       memset(&child, 0, sizeof(child));
-       child.argv = args;
-       args[0] = "sh";
-       args[1] = "-c";
-       args[2] = cmdbuf;
-       args[3] = NULL;
-
-       status = run_command(&child);
-       if (status < -ERR_RUN_COMMAND_FORK)
-               ; /* failure in run-command */
-       else
-               status = -status;
-       fd = open(temp[1], O_RDONLY);
-       if (fd < 0)
-               goto bad;
-       if (fstat(fd, &st))
-               goto close_bad;
-       result->size = st.st_size;
-       result->ptr = xmalloc(result->size + 1);
-       if (read_in_full(fd, result->ptr, result->size) != result->size) {
-               free(result->ptr);
-               result->ptr = NULL;
-               result->size = 0;
-       }
- close_bad:
-       close(fd);
- bad:
-       for (i = 0; i < 3; i++)
-               unlink(temp[i]);
-       return status;
-}
-
-/*
- * merge.default and merge.driver configuration items
- */
-static struct ll_merge_driver *ll_user_merge, **ll_user_merge_tail;
-static const char *default_ll_merge;
-
-static int read_merge_config(const char *var, const char *value)
-{
-       struct ll_merge_driver *fn;
-       const char *ep, *name;
-       int namelen;
-
-       if (!strcmp(var, "merge.default")) {
-               if (value)
-                       default_ll_merge = strdup(value);
-               return 0;
-       }
-
-       /*
-        * We are not interested in anything but "merge.<name>.variable";
-        * especially, we do not want to look at variables such as
-        * "merge.summary", "merge.tool", and "merge.verbosity".
-        */
-       if (prefixcmp(var, "merge.") || (ep = strrchr(var, '.')) == var + 5)
-               return 0;
-
-       /*
-        * Find existing one as we might be processing merge.<name>.var2
-        * after seeing merge.<name>.var1.
-        */
-       name = var + 6;
-       namelen = ep - name;
-       for (fn = ll_user_merge; fn; fn = fn->next)
-               if (!strncmp(fn->name, name, namelen) && !fn->name[namelen])
-                       break;
-       if (!fn) {
-               fn = xcalloc(1, sizeof(struct ll_merge_driver));
-               fn->name = xmemdupz(name, namelen);
-               fn->fn = ll_ext_merge;
-               *ll_user_merge_tail = fn;
-               ll_user_merge_tail = &(fn->next);
-       }
-
-       ep++;
-
-       if (!strcmp("name", ep)) {
-               if (!value)
-                       return error("%s: lacks value", var);
-               fn->description = strdup(value);
-               return 0;
-       }
-
-       if (!strcmp("driver", ep)) {
-               if (!value)
-                       return error("%s: lacks value", var);
-               /*
-                * merge.<name>.driver specifies the command line:
-                *
-                *      command-line
-                *
-                * The command-line will be interpolated with the following
-                * tokens and is given to the shell:
-                *
-                *    %O - temporary file name for the merge base.
-                *    %A - temporary file name for our version.
-                *    %B - temporary file name for the other branches' version.
-                *
-                * The external merge driver should write the results in the
-                * file named by %A, and signal that it has done with zero exit
-                * status.
-                */
-               fn->cmdline = strdup(value);
-               return 0;
-       }
-
-       if (!strcmp("recursive", ep)) {
-               if (!value)
-                       return error("%s: lacks value", var);
-               fn->recursive = strdup(value);
-               return 0;
-       }
-
-       return 0;
-}
-
-static void initialize_ll_merge(void)
-{
-       if (ll_user_merge_tail)
-               return;
-       ll_user_merge_tail = &ll_user_merge;
-       git_config(read_merge_config);
-}
-
-static const struct ll_merge_driver *find_ll_merge_driver(const char *merge_attr)
-{
-       struct ll_merge_driver *fn;
-       const char *name;
-       int i;
-
-       initialize_ll_merge();
-
-       if (ATTR_TRUE(merge_attr))
-               return &ll_merge_drv[LL_TEXT_MERGE];
-       else if (ATTR_FALSE(merge_attr))
-               return &ll_merge_drv[LL_BINARY_MERGE];
-       else if (ATTR_UNSET(merge_attr)) {
-               if (!default_ll_merge)
-                       return &ll_merge_drv[LL_TEXT_MERGE];
-               else
-                       name = default_ll_merge;
-       }
-       else
-               name = merge_attr;
-
-       for (fn = ll_user_merge; fn; fn = fn->next)
-               if (!strcmp(fn->name, name))
-                       return fn;
-
-       for (i = 0; i < ARRAY_SIZE(ll_merge_drv); i++)
-               if (!strcmp(ll_merge_drv[i].name, name))
-                       return &ll_merge_drv[i];
-
-       /* default to the 3-way */
-       return &ll_merge_drv[LL_TEXT_MERGE];
-}
-
-static const char *git_path_check_merge(const char *path)
-{
-       static struct git_attr_check attr_merge_check;
-
-       if (!attr_merge_check.attr)
-               attr_merge_check.attr = git_attr("merge", 5);
-
-       if (git_checkattr(path, 1, &attr_merge_check))
-               return NULL;
-       return attr_merge_check.value;
-}
-
-static int ll_merge(mmbuffer_t *result_buf,
-                   struct diff_filespec *o,
-                   struct diff_filespec *a,
-                   struct diff_filespec *b,
-                   const char *branch1,
-                   const char *branch2)
+static int merge_3way(struct merge_options *o,
+                     mmbuffer_t *result_buf,
+                     struct diff_filespec *one,
+                     struct diff_filespec *a,
+                     struct diff_filespec *b,
+                     const char *branch1,
+                     const char *branch2)
 {
        mmfile_t orig, src1, src2;
        char *name1, *name2;
        int merge_status;
-       const char *ll_driver_name;
-       const struct ll_merge_driver *driver;
 
        name1 = xstrdup(mkpath("%s:%s", branch1, a->path));
        name2 = xstrdup(mkpath("%s:%s", branch2, b->path));
 
-       fill_mm(o->sha1, &orig);
+       fill_mm(one->sha1, &orig);
        fill_mm(a->sha1, &src1);
        fill_mm(b->sha1, &src2);
 
-       ll_driver_name = git_path_check_merge(a->path);
-       driver = find_ll_merge_driver(ll_driver_name);
-
-       if (index_only && driver->recursive)
-               driver = find_ll_merge_driver(driver->recursive);
-       merge_status = driver->fn(driver, a->path,
-                                 &orig, &src1, name1, &src2, name2,
-                                 result_buf);
+       merge_status = ll_merge(result_buf, a->path, &orig,
+                               &src1, name1, &src2, name2,
+                               o->call_depth);
 
        free(name1);
        free(name2);
@@ -1002,9 +605,12 @@ static int ll_merge(mmbuffer_t *result_buf,
        return merge_status;
 }
 
-static struct merge_file_info merge_file(struct diff_filespec *o,
-               struct diff_filespec *a, struct diff_filespec *b,
-               const char *branch1, const char *branch2)
+static struct merge_file_info merge_file(struct merge_options *o,
+                                        struct diff_filespec *one,
+                                        struct diff_filespec *a,
+                                        struct diff_filespec *b,
+                                        const char *branch1,
+                                        const char *branch2)
 {
        struct merge_file_info result;
        result.merge = 0;
@@ -1020,21 +626,32 @@ static struct merge_file_info merge_file(struct diff_filespec *o,
                        hashcpy(result.sha, b->sha1);
                }
        } else {
-               if (!sha_eq(a->sha1, o->sha1) && !sha_eq(b->sha1, o->sha1))
+               if (!sha_eq(a->sha1, one->sha1) && !sha_eq(b->sha1, one->sha1))
                        result.merge = 1;
 
-               result.mode = a->mode == o->mode ? b->mode: a->mode;
+               /*
+                * Merge modes
+                */
+               if (a->mode == b->mode || a->mode == one->mode)
+                       result.mode = b->mode;
+               else {
+                       result.mode = a->mode;
+                       if (b->mode != one->mode) {
+                               result.clean = 0;
+                               result.merge = 1;
+                       }
+               }
 
-               if (sha_eq(a->sha1, o->sha1))
+               if (sha_eq(a->sha1, b->sha1) || sha_eq(a->sha1, one->sha1))
                        hashcpy(result.sha, b->sha1);
-               else if (sha_eq(b->sha1, o->sha1))
+               else if (sha_eq(b->sha1, one->sha1))
                        hashcpy(result.sha, a->sha1);
                else if (S_ISREG(a->mode)) {
                        mmbuffer_t result_buf;
                        int merge_status;
 
-                       merge_status = ll_merge(&result_buf, o, a, b,
-                                               branch1, branch2);
+                       merge_status = merge_3way(o, &result_buf, one, a, b,
+                                                 branch1, branch2);
 
                        if ((merge_status < 0) || !result_buf.ptr)
                                die("Failed to execute internal merge");
@@ -1046,21 +663,24 @@ static struct merge_file_info merge_file(struct diff_filespec *o,
 
                        free(result_buf.ptr);
                        result.clean = (merge_status == 0);
-               } else {
-                       if (!(S_ISLNK(a->mode) || S_ISLNK(b->mode)))
-                               die("cannot merge modes?");
-
+               } else if (S_ISGITLINK(a->mode)) {
+                       result.clean = 0;
+                       hashcpy(result.sha, a->sha1);
+               } else if (S_ISLNK(a->mode)) {
                        hashcpy(result.sha, a->sha1);
 
                        if (!sha_eq(a->sha1, b->sha1))
                                result.clean = 0;
+               } else {
+                       die("unsupported object type in the tree");
                }
        }
 
        return result;
 }
 
-static void conflict_rename_rename(struct rename *ren1,
+static void conflict_rename_rename(struct merge_options *o,
+                                  struct rename *ren1,
                                   const char *branch1,
                                   struct rename *ren2,
                                   const char *branch2)
@@ -1071,26 +691,26 @@ static void conflict_rename_rename(struct rename *ren1,
        const char *ren2_dst = ren2->pair->two->path;
        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(1, "%s is a directory in %s added as %s instead",
+       if (string_list_has_string(&o->current_directory_set, ren1_dst)) {
+               dst_name1 = del[delp++] = unique_path(o, ren1_dst, branch1);
+               output(o, 1, "%s is a directory in %s adding as %s instead",
                       ren1_dst, branch2, dst_name1);
-               remove_file(0, ren1_dst, 0);
+               remove_file(o, 0, ren1_dst, 0);
        }
-       if (path_list_has_path(&current_directory_set, ren2_dst)) {
-               dst_name2 = del[delp++] = unique_path(ren2_dst, branch2);
-               output(1, "%s is a directory in %s added as %s instead",
+       if (string_list_has_string(&o->current_directory_set, ren2_dst)) {
+               dst_name2 = del[delp++] = unique_path(o, ren2_dst, branch2);
+               output(o, 1, "%s is a directory in %s adding as %s instead",
                       ren2_dst, branch1, dst_name2);
-               remove_file(0, ren2_dst, 0);
+               remove_file(o, 0, ren2_dst, 0);
        }
-       if (index_only) {
+       if (o->call_depth) {
                remove_file_from_cache(dst_name1);
                remove_file_from_cache(dst_name2);
                /*
                 * Uncomment to leave the conflicting names in the resulting tree
                 *
-                * update_file(0, ren1->pair->two->sha1, ren1->pair->two->mode, dst_name1);
-                * update_file(0, ren2->pair->two->sha1, ren2->pair->two->mode, dst_name2);
+                * update_file(o, 0, ren1->pair->two->sha1, ren1->pair->two->mode, dst_name1);
+                * update_file(o, 0, ren2->pair->two->sha1, ren2->pair->two->mode, dst_name2);
                 */
        } else {
                update_stages(dst_name1, NULL, ren1->pair->two, NULL, 1);
@@ -1100,57 +720,58 @@ static void conflict_rename_rename(struct rename *ren1,
                free(del[delp]);
 }
 
-static void conflict_rename_dir(struct rename *ren1,
+static void conflict_rename_dir(struct merge_options *o,
+                               struct rename *ren1,
                                const char *branch1)
 {
-       char *new_path = unique_path(ren1->pair->two->path, branch1);
-       output(1, "Renamed %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);
+       char *new_path = unique_path(o, ren1->pair->two->path, branch1);
+       output(o, 1, "Renaming %s to %s instead", ren1->pair->one->path, new_path);
+       remove_file(o, 0, ren1->pair->two->path, 0);
+       update_file(o, 0, ren1->pair->two->sha1, ren1->pair->two->mode, new_path);
        free(new_path);
 }
 
-static void conflict_rename_rename_2(struct rename *ren1,
+static void conflict_rename_rename_2(struct merge_options *o,
+                                    struct rename *ren1,
                                     const char *branch1,
                                     struct rename *ren2,
                                     const char *branch2)
 {
-       char *new_path1 = unique_path(ren1->pair->two->path, branch1);
-       char *new_path2 = unique_path(ren2->pair->two->path, branch2);
-       output(1, "Renamed %s to %s and %s to %s instead",
+       char *new_path1 = unique_path(o, ren1->pair->two->path, branch1);
+       char *new_path2 = unique_path(o, ren2->pair->two->path, branch2);
+       output(o, 1, "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, 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);
+       remove_file(o, 0, ren1->pair->two->path, 0);
+       update_file(o, 0, ren1->pair->two->sha1, ren1->pair->two->mode, new_path1);
+       update_file(o, 0, ren2->pair->two->sha1, ren2->pair->two->mode, new_path2);
        free(new_path2);
        free(new_path1);
 }
 
-static int process_renames(struct path_list *a_renames,
-                          struct path_list *b_renames,
-                          const char *a_branch,
-                          const char *b_branch)
+static int process_renames(struct merge_options *o,
+                          struct string_list *a_renames,
+                          struct string_list *b_renames)
 {
        int clean_merge = 1, i, j;
-       struct path_list a_by_dst = {NULL, 0, 0, 0}, b_by_dst = {NULL, 0, 0, 0};
+       struct string_list a_by_dst = {NULL, 0, 0, 0}, b_by_dst = {NULL, 0, 0, 0};
        const struct rename *sre;
 
        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
+               string_list_insert(sre->pair->two->path, &a_by_dst)->util
                        = sre->dst_entry;
        }
        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
+               string_list_insert(sre->pair->two->path, &b_by_dst)->util
                        = sre->dst_entry;
        }
 
        for (i = 0, j = 0; i < a_renames->nr || j < b_renames->nr;) {
                int compare;
                char *src;
-               struct path_list *renames1, *renames2, *renames2Dst;
+               struct string_list *renames1, *renames2, *renames2Dst;
                struct rename *ren1 = NULL, *ren2 = NULL;
                const char *branch1, *branch2;
                const char *ren1_src, *ren1_dst;
@@ -1162,8 +783,8 @@ static int process_renames(struct path_list *a_renames,
                        compare = -1;
                        ren1 = a_renames->items[i++].util;
                } else {
-                       compare = strcmp(a_renames->items[i].path,
-                                       b_renames->items[j].path);
+                       compare = strcmp(a_renames->items[i].string,
+                                       b_renames->items[j].string);
                        if (compare <= 0)
                                ren1 = a_renames->items[i++].util;
                        if (compare >= 0)
@@ -1175,15 +796,15 @@ static int process_renames(struct path_list *a_renames,
                        renames1 = a_renames;
                        renames2 = b_renames;
                        renames2Dst = &b_by_dst;
-                       branch1 = a_branch;
-                       branch2 = b_branch;
+                       branch1 = o->branch1;
+                       branch2 = o->branch2;
                } else {
                        struct rename *tmp;
                        renames1 = b_renames;
                        renames2 = a_renames;
                        renames2Dst = &a_by_dst;
-                       branch1 = b_branch;
-                       branch2 = a_branch;
+                       branch1 = o->branch2;
+                       branch2 = o->branch1;
                        tmp = ren2;
                        ren2 = ren1;
                        ren1 = tmp;
@@ -1210,54 +831,55 @@ static int process_renames(struct path_list *a_renames,
                        ren2->processed = 1;
                        if (strcmp(ren1_dst, ren2_dst) != 0) {
                                clean_merge = 0;
-                               output(1, "CONFLICT (rename/rename): "
+                               output(o, 1, "CONFLICT (rename/rename): "
                                       "Rename \"%s\"->\"%s\" in branch \"%s\" "
                                       "rename \"%s\"->\"%s\" in \"%s\"%s",
                                       src, ren1_dst, branch1,
                                       src, ren2_dst, branch2,
-                                      index_only ? " (left unresolved)": "");
-                               if (index_only) {
+                                      o->call_depth ? " (left unresolved)": "");
+                               if (o->call_depth) {
                                        remove_file_from_cache(src);
-                                       update_file(0, ren1->pair->one->sha1,
+                                       update_file(o, 0, ren1->pair->one->sha1,
                                                    ren1->pair->one->mode, src);
                                }
-                               conflict_rename_rename(ren1, branch1, ren2, branch2);
+                               conflict_rename_rename(o, ren1, branch1, ren2, branch2);
                        } else {
                                struct merge_file_info mfi;
-                               remove_file(1, ren1_src, 1);
-                               mfi = merge_file(ren1->pair->one,
+                               remove_file(o, 1, ren1_src, 1);
+                               mfi = merge_file(o,
+                                                ren1->pair->one,
                                                 ren1->pair->two,
                                                 ren2->pair->two,
                                                 branch1,
                                                 branch2);
                                if (mfi.merge || !mfi.clean)
-                                       output(1, "Renamed %s->%s", src, ren1_dst);
+                                       output(o, 1, "Renaming %s->%s", src, ren1_dst);
 
                                if (mfi.merge)
-                                       output(2, "Auto-merged %s", ren1_dst);
+                                       output(o, 2, "Auto-merging %s", ren1_dst);
 
                                if (!mfi.clean) {
-                                       output(1, "CONFLICT (content): merge conflict in %s",
+                                       output(o, 1, "CONFLICT (content): merge conflict in %s",
                                               ren1_dst);
                                        clean_merge = 0;
 
-                                       if (!index_only)
+                                       if (!o->call_depth)
                                                update_stages(ren1_dst,
                                                              ren1->pair->one,
                                                              ren1->pair->two,
                                                              ren2->pair->two,
                                                              1 /* clear */);
                                }
-                               update_file(mfi.clean, mfi.sha, mfi.mode, ren1_dst);
+                               update_file(o, mfi.clean, mfi.sha, mfi.mode, ren1_dst);
                        }
                } else {
                        /* Renamed in 1, maybe changed in 2 */
-                       struct path_list_item *item;
+                       struct string_list_item *item;
                        /* we only use sha1 and mode of these */
                        struct diff_filespec src_other, dst_other;
                        int try_merge, stage = a_renames == renames1 ? 3: 2;
 
-                       remove_file(1, ren1_src, index_only || stage == 3);
+                       remove_file(o, 1, ren1_src, o->call_depth || stage == 3);
 
                        hashcpy(src_other.sha1, ren1->src_entry->stages[stage].sha);
                        src_other.mode = ren1->src_entry->stages[stage].mode;
@@ -1266,49 +888,50 @@ static int process_renames(struct path_list *a_renames,
 
                        try_merge = 0;
 
-                       if (path_list_has_path(&current_directory_set, ren1_dst)) {
+                       if (string_list_has_string(&o->current_directory_set, ren1_dst)) {
                                clean_merge = 0;
-                               output(1, "CONFLICT (rename/directory): Renamed %s->%s in %s "
+                               output(o, 1, "CONFLICT (rename/directory): Rename %s->%s in %s "
                                       " directory %s added in %s",
                                       ren1_src, ren1_dst, branch1,
                                       ren1_dst, branch2);
-                               conflict_rename_dir(ren1, branch1);
+                               conflict_rename_dir(o, ren1, branch1);
                        } else if (sha_eq(src_other.sha1, null_sha1)) {
                                clean_merge = 0;
-                               output(1, "CONFLICT (rename/delete): Renamed %s->%s in %s "
+                               output(o, 1, "CONFLICT (rename/delete): Rename %s->%s in %s "
                                       "and deleted in %s",
                                       ren1_src, ren1_dst, branch1,
                                       branch2);
-                               update_file(0, ren1->pair->two->sha1, ren1->pair->two->mode, ren1_dst);
+                               update_file(o, 0, ren1->pair->two->sha1, ren1->pair->two->mode, ren1_dst);
                        } else if (!sha_eq(dst_other.sha1, null_sha1)) {
                                const char *new_path;
                                clean_merge = 0;
                                try_merge = 1;
-                               output(1, "CONFLICT (rename/add): Renamed %s->%s in %s. "
+                               output(o, 1, "CONFLICT (rename/add): Rename %s->%s in %s. "
                                       "%s added in %s",
                                       ren1_src, ren1_dst, branch1,
                                       ren1_dst, branch2);
-                               new_path = unique_path(ren1_dst, branch2);
-                               output(1, "Added 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))) {
+                               new_path = unique_path(o, ren1_dst, branch2);
+                               output(o, 1, "Adding as %s instead", new_path);
+                               update_file(o, 0, dst_other.sha1, dst_other.mode, new_path);
+                       } else if ((item = string_list_lookup(ren1_dst, renames2Dst))) {
                                ren2 = item->util;
                                clean_merge = 0;
                                ren2->processed = 1;
-                               output(1, "CONFLICT (rename/rename): Renamed %s->%s in %s. "
-                                      "Renamed %s->%s in %s",
+                               output(o, 1, "CONFLICT (rename/rename): "
+                                      "Rename %s->%s in %s. "
+                                      "Rename %s->%s in %s",
                                       ren1_src, ren1_dst, branch1,
                                       ren2->pair->one->path, ren2->pair->two->path, branch2);
-                               conflict_rename_rename_2(ren1, branch1, ren2, branch2);
+                               conflict_rename_rename_2(o, ren1, branch1, ren2, branch2);
                        } else
                                try_merge = 1;
 
                        if (try_merge) {
-                               struct diff_filespec *o, *a, *b;
+                               struct diff_filespec *one, *a, *b;
                                struct merge_file_info mfi;
                                src_other.path = (char *)ren1_src;
 
-                               o = ren1->pair->one;
+                               one = ren1->pair->one;
                                if (a_renames == renames1) {
                                        a = ren1->pair->two;
                                        b = &src_other;
@@ -1316,8 +939,8 @@ static int process_renames(struct path_list *a_renames,
                                        b = ren1->pair->two;
                                        a = &src_other;
                                }
-                               mfi = merge_file(o, a, b,
-                                               a_branch, b_branch);
+                               mfi = merge_file(o, one, a, b,
+                                               o->branch1, o->branch2);
 
                                if (mfi.clean &&
                                    sha_eq(mfi.sha, ren1->pair->two->sha1) &&
@@ -1327,28 +950,28 @@ static int process_renames(struct path_list *a_renames,
                                         * t6022 test. If you change
                                         * it update the test too.
                                         */
-                                       output(3, "Skipped %s (merged same as existing)", ren1_dst);
+                                       output(o, 3, "Skipped %s (merged same as existing)", ren1_dst);
                                else {
                                        if (mfi.merge || !mfi.clean)
-                                               output(1, "Renamed %s => %s", ren1_src, ren1_dst);
+                                               output(o, 1, "Renaming %s => %s", ren1_src, ren1_dst);
                                        if (mfi.merge)
-                                               output(2, "Auto-merged %s", ren1_dst);
+                                               output(o, 2, "Auto-merging %s", ren1_dst);
                                        if (!mfi.clean) {
-                                               output(1, "CONFLICT (rename/modify): Merge conflict in %s",
+                                               output(o, 1, "CONFLICT (rename/modify): Merge conflict in %s",
                                                       ren1_dst);
                                                clean_merge = 0;
 
-                                               if (!index_only)
+                                               if (!o->call_depth)
                                                        update_stages(ren1_dst,
-                                                                     o, a, b, 1);
+                                                                     one, a, b, 1);
                                        }
-                                       update_file(mfi.clean, mfi.sha, mfi.mode, ren1_dst);
+                                       update_file(o, mfi.clean, mfi.sha, mfi.mode, ren1_dst);
                                }
                        }
                }
        }
-       path_list_clear(&a_by_dst, 0);
-       path_list_clear(&b_by_dst, 0);
+       string_list_clear(&a_by_dst, 0);
+       string_list_clear(&b_by_dst, 0);
 
        return clean_merge;
 }
@@ -1359,9 +982,8 @@ static unsigned char *stage_sha(const unsigned char *sha, unsigned mode)
 }
 
 /* Per entry merge function */
-static int process_entry(const char *path, struct stage_data *entry,
-                        const char *branch1,
-                        const char *branch2)
+static int process_entry(struct merge_options *o,
+                        const char *path, struct stage_data *entry)
 {
        /*
        printf("processing entry, clean cache: %s\n", index_only ? "yes": "no");
@@ -1383,24 +1005,24 @@ static int process_entry(const char *path, struct stage_data *entry,
                        /* Deleted in both or deleted in one and
                         * unchanged in the other */
                        if (a_sha)
-                               output(2, "Removed %s", path);
+                               output(o, 2, "Removing %s", path);
                        /* do not touch working file if it did not exist */
-                       remove_file(1, path, !a_sha);
+                       remove_file(o, 1, path, !a_sha);
                } else {
                        /* Deleted in one and changed in the other */
                        clean_merge = 0;
                        if (!a_sha) {
-                               output(1, "CONFLICT (delete/modify): %s deleted in %s "
+                               output(o, 1, "CONFLICT (delete/modify): %s deleted in %s "
                                       "and modified in %s. Version %s of %s left in tree.",
-                                      path, branch1,
-                                      branch2, branch2, path);
-                               update_file(0, b_sha, b_mode, path);
+                                      path, o->branch1,
+                                      o->branch2, o->branch2, path);
+                               update_file(o, 0, b_sha, b_mode, path);
                        } else {
-                               output(1, "CONFLICT (delete/modify): %s deleted in %s "
+                               output(o, 1, "CONFLICT (delete/modify): %s deleted in %s "
                                       "and modified in %s. Version %s of %s left in tree.",
-                                      path, branch2,
-                                      branch1, branch1, path);
-                               update_file(0, a_sha, a_mode, path);
+                                      path, o->branch2,
+                                      o->branch1, o->branch1, path);
+                               update_file(o, 0, a_sha, a_mode, path);
                        }
                }
 
@@ -1414,64 +1036,67 @@ static int process_entry(const char *path, struct stage_data *entry,
                const char *conf;
 
                if (a_sha) {
-                       add_branch = branch1;
-                       other_branch = branch2;
+                       add_branch = o->branch1;
+                       other_branch = o->branch2;
                        mode = a_mode;
                        sha = a_sha;
                        conf = "file/directory";
                } else {
-                       add_branch = branch2;
-                       other_branch = branch1;
+                       add_branch = o->branch2;
+                       other_branch = o->branch1;
                        mode = b_mode;
                        sha = b_sha;
                        conf = "directory/file";
                }
-               if (path_list_has_path(&current_directory_set, path)) {
-                       const char *new_path = unique_path(path, add_branch);
+               if (string_list_has_string(&o->current_directory_set, path)) {
+                       const char *new_path = unique_path(o, path, add_branch);
                        clean_merge = 0;
-                       output(1, "CONFLICT (%s): There is a directory with name %s in %s. "
-                              "Added %s as %s",
+                       output(o, 1, "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, 0);
-                       update_file(0, sha, mode, new_path);
+                       remove_file(o, 0, path, 0);
+                       update_file(o, 0, sha, mode, new_path);
                } else {
-                       output(2, "Added %s", path);
-                       update_file(1, sha, mode, path);
+                       output(o, 2, "Adding %s", path);
+                       update_file(o, 1, sha, mode, path);
                }
        } 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;
+               struct diff_filespec one, a, b;
 
                if (!o_sha) {
                        reason = "add/add";
                        o_sha = (unsigned char *)null_sha1;
                }
-               output(2, "Auto-merged %s", path);
-               o.path = a.path = b.path = (char *)path;
-               hashcpy(o.sha1, o_sha);
-               o.mode = o_mode;
+               output(o, 2, "Auto-merging %s", path);
+               one.path = a.path = b.path = (char *)path;
+               hashcpy(one.sha1, o_sha);
+               one.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,
-                                branch1, branch2);
+               mfi = merge_file(o, &one, &a, &b,
+                                o->branch1, o->branch2);
 
+               clean_merge = mfi.clean;
                if (mfi.clean)
-                       update_file(1, mfi.sha, mfi.mode, path);
+                       update_file(o, 1, mfi.sha, mfi.mode, path);
+               else if (S_ISGITLINK(mfi.mode))
+                       output(o, 1, "CONFLICT (submodule): Merge conflict in %s "
+                              "- needs %s", path, sha1_to_hex(b.sha1));
                else {
-                       clean_merge = 0;
-                       output(1, "CONFLICT (%s): Merge conflict in %s",
+                       output(o, 1, "CONFLICT (%s): Merge conflict in %s",
                                        reason, path);
 
-                       if (index_only)
-                               update_file(0, mfi.sha, mfi.mode, path);
+                       if (o->call_depth)
+                               update_file(o, 0, mfi.sha, mfi.mode, path);
                        else
-                               update_file_flags(mfi.sha, mfi.mode, path,
+                               update_file_flags(o, mfi.sha, mfi.mode, path,
                                              0 /* update_cache */, 1 /* update_working_directory */);
                }
        } else if (!o_sha && !a_sha && !b_sha) {
@@ -1479,71 +1104,69 @@ static int process_entry(const char *path, struct stage_data *entry,
                 * this entry was deleted altogether. a_mode == 0 means
                 * we had that path and want to actively remove it.
                 */
-               remove_file(1, path, !a_mode);
+               remove_file(o, 1, path, !a_mode);
        } else
                die("Fatal merge failure, shouldn't happen.");
 
        return clean_merge;
 }
 
-static int merge_trees(struct tree *head,
-                      struct tree *merge,
-                      struct tree *common,
-                      const char *branch1,
-                      const char *branch2,
-                      struct tree **result)
+int merge_trees(struct merge_options *o,
+               struct tree *head,
+               struct tree *merge,
+               struct tree *common,
+               struct tree **result)
 {
        int code, clean;
 
-       if (subtree_merge) {
+       if (o->subtree_merge) {
                merge = shift_tree_object(head, merge);
                common = shift_tree_object(head, common);
        }
 
        if (sha_eq(common->object.sha1, merge->object.sha1)) {
-               output(0, "Already uptodate!");
+               output(o, 0, "Already uptodate!");
                *result = head;
                return 1;
        }
 
-       code = git_merge_trees(index_only, common, head, merge);
+       code = git_merge_trees(o->call_depth, common, head, merge);
 
        if (code != 0)
                die("merging of trees %s and %s failed",
                    sha1_to_hex(head->object.sha1),
                    sha1_to_hex(merge->object.sha1));
 
-       if (unmerged_index()) {
-               struct path_list *entries, *re_head, *re_merge;
+       if (unmerged_cache()) {
+               struct string_list *entries, *re_head, *re_merge;
                int i;
-               path_list_clear(&current_file_set, 1);
-               path_list_clear(&current_directory_set, 1);
-               get_files_dirs(head);
-               get_files_dirs(merge);
+               string_list_clear(&o->current_file_set, 1);
+               string_list_clear(&o->current_directory_set, 1);
+               get_files_dirs(o, head);
+               get_files_dirs(o, merge);
 
                entries = get_unmerged();
-               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,
-                               branch1, branch2);
+               re_head  = get_renames(o, head, common, head, merge, entries);
+               re_merge = get_renames(o, merge, common, head, merge, entries);
+               clean = process_renames(o, re_head, re_merge);
                for (i = 0; i < entries->nr; i++) {
-                       const char *path = entries->items[i].path;
+                       const char *path = entries->items[i].string;
                        struct stage_data *e = entries->items[i].util;
                        if (!e->processed
-                               && !process_entry(path, e, branch1, branch2))
+                               && !process_entry(o, path, e))
                                clean = 0;
                }
 
-               path_list_clear(re_merge, 0);
-               path_list_clear(re_head, 0);
-               path_list_clear(entries, 1);
+               string_list_clear(re_merge, 0);
+               string_list_clear(re_head, 0);
+               string_list_clear(entries, 1);
 
        }
        else
                clean = 1;
 
-       if (index_only)
-               *result = git_write_tree();
+       if (o->call_depth)
+               *result = write_tree_from_memory(o);
 
        return clean;
 }
@@ -1563,22 +1186,21 @@ static struct commit_list *reverse_commit_list(struct commit_list *list)
  * Merge the commits h1 and h2, return the resulting virtual
  * commit object and a flag indicating the cleanness of the merge.
  */
-static int merge(struct commit *h1,
-                struct commit *h2,
-                const char *branch1,
-                const char *branch2,
-                struct commit_list *ca,
-                struct commit **result)
+int merge_recursive(struct merge_options *o,
+                   struct commit *h1,
+                   struct commit *h2,
+                   struct commit_list *ca,
+                   struct commit **result)
 {
        struct commit_list *iter;
        struct commit *merged_common_ancestors;
        struct tree *mrtree = mrtree;
        int clean;
 
-       if (show(4)) {
-               output(4, "Merging:");
-               output_commit_title(h1);
-               output_commit_title(h2);
+       if (show(o, 4)) {
+               output(o, 4, "Merging:");
+               output_commit_title(o, h1);
+               output_commit_title(o, h2);
        }
 
        if (!ca) {
@@ -1586,10 +1208,10 @@ static int merge(struct commit *h1,
                ca = reverse_commit_list(ca);
        }
 
-       if (show(5)) {
-               output(5, "found %u common ancestor(s):", commit_list_count(ca));
+       if (show(o, 5)) {
+               output(o, 5, "found %u common ancestor(s):", commit_list_count(ca));
                for (iter = ca; iter; iter = iter->next)
-                       output_commit_title(iter->item);
+                       output_commit_title(o, iter->item);
        }
 
        merged_common_ancestors = pop_commit(&ca);
@@ -1604,7 +1226,8 @@ static int merge(struct commit *h1,
        }
 
        for (iter = ca; iter; iter = iter->next) {
-               call_depth++;
+               const char *saved_b1, *saved_b2;
+               o->call_depth++;
                /*
                 * When the merge fails, the result contains files
                 * with conflict markers. The cleanness flag is
@@ -1613,139 +1236,121 @@ static int merge(struct commit *h1,
                 * "conflicts" were already resolved.
                 */
                discard_cache();
-               merge(merged_common_ancestors, iter->item,
-                     "Temporary merge branch 1",
-                     "Temporary merge branch 2",
-                     NULL,
-                     &merged_common_ancestors);
-               call_depth--;
+               saved_b1 = o->branch1;
+               saved_b2 = o->branch2;
+               o->branch1 = "Temporary merge branch 1";
+               o->branch2 = "Temporary merge branch 2";
+               merge_recursive(o, merged_common_ancestors, iter->item,
+                               NULL, &merged_common_ancestors);
+               o->branch1 = saved_b1;
+               o->branch2 = saved_b2;
+               o->call_depth--;
 
                if (!merged_common_ancestors)
                        die("merge returned no commit");
        }
 
        discard_cache();
-       if (!call_depth) {
+       if (!o->call_depth)
                read_cache();
-               index_only = 0;
-       } else
-               index_only = 1;
 
-       clean = merge_trees(h1->tree, h2->tree, merged_common_ancestors->tree,
-                           branch1, branch2, &mrtree);
+       clean = merge_trees(o, h1->tree, h2->tree, merged_common_ancestors->tree,
+                           &mrtree);
 
-       if (index_only) {
+       if (o->call_depth) {
                *result = make_virtual_commit(mrtree, "merged tree");
                commit_list_insert(h1, &(*result)->parents);
                commit_list_insert(h2, &(*result)->parents->next);
        }
-       flush_output();
+       flush_output(o);
        return clean;
 }
 
-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;
-}
-
-static struct commit *get_ref(const char *ref)
+static struct commit *get_ref(const unsigned char *sha1, const char *name)
 {
-       unsigned char sha1[20];
        struct object *object;
 
-       if (get_sha1(ref, sha1))
-               die("Could not resolve ref '%s'", ref);
-       object = deref_tag(parse_object(sha1), ref, strlen(ref));
+       object = deref_tag(parse_object(sha1), name, strlen(name));
+       if (!object)
+               return NULL;
        if (object->type == OBJ_TREE)
-               return make_virtual_commit((struct tree*)object,
-                       better_branch_name(ref));
+               return make_virtual_commit((struct tree*)object, name);
        if (object->type != OBJ_COMMIT)
                return NULL;
        if (parse_commit((struct commit *)object))
-               die("Could not parse commit '%s'", sha1_to_hex(object->sha1));
+               return NULL;
        return (struct commit *)object;
 }
 
-static int merge_config(const char *var, const char *value)
+int merge_recursive_generic(struct merge_options *o,
+                           const unsigned char *head,
+                           const unsigned char *merge,
+                           int num_base_list,
+                           const unsigned char **base_list,
+                           struct commit **result)
 {
+       int clean, index_fd;
+       struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
+       struct commit *head_commit = get_ref(head, o->branch1);
+       struct commit *next_commit = get_ref(merge, o->branch2);
+       struct commit_list *ca = NULL;
+
+       if (base_list) {
+               int i;
+               for (i = 0; i < num_base_list; ++i) {
+                       struct commit *base;
+                       if (!(base = get_ref(base_list[i], sha1_to_hex(base_list[i]))))
+                               return error("Could not parse object '%s'",
+                                       sha1_to_hex(base_list[i]));
+                       commit_list_insert(base, &ca);
+               }
+       }
+
+       index_fd = hold_locked_index(lock, 1);
+       clean = merge_recursive(o, head_commit, next_commit, ca,
+                       result);
+       if (active_cache_changed &&
+                       (write_cache(index_fd, active_cache, active_nr) ||
+                        commit_locked_index(lock)))
+               return error("Unable to write index.");
+
+       return clean ? 0 : 1;
+}
+
+static int merge_recursive_config(const char *var, const char *value, void *cb)
+{
+       struct merge_options *o = cb;
        if (!strcasecmp(var, "merge.verbosity")) {
-               verbosity = git_config_int(var, value);
+               o->verbosity = git_config_int(var, value);
                return 0;
        }
        if (!strcasecmp(var, "diff.renamelimit")) {
-               rename_limit = git_config_int(var, value);
+               o->diff_rename_limit = git_config_int(var, value);
+               return 0;
+       }
+       if (!strcasecmp(var, "merge.renamelimit")) {
+               o->merge_rename_limit = git_config_int(var, value);
                return 0;
        }
-       return git_default_config(var, value);
+       return git_xmerge_config(var, value, cb);
 }
 
-int main(int argc, char *argv[])
+void init_merge_options(struct merge_options *o)
 {
-       static const char *bases[20];
-       static unsigned bases_count = 0;
-       int i, clean;
-       const char *branch1, *branch2;
-       struct commit *result, *h1, *h2;
-       struct commit_list *ca = NULL;
-       struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
-       int index_fd;
-
-       if (argv[0]) {
-               int namelen = strlen(argv[0]);
-               if (8 < namelen &&
-                   !strcmp(argv[0] + namelen - 8, "-subtree"))
-                       subtree_merge = 1;
-       }
-
-       git_config(merge_config);
+       memset(o, 0, sizeof(struct merge_options));
+       o->verbosity = 2;
+       o->buffer_output = 1;
+       o->diff_rename_limit = -1;
+       o->merge_rename_limit = -1;
+       git_config(merge_recursive_config, o);
        if (getenv("GIT_MERGE_VERBOSITY"))
-               verbosity = strtol(getenv("GIT_MERGE_VERBOSITY"), NULL, 10);
-
-       if (argc < 4)
-               die("Usage: %s <base>... -- <head> <remote> ...\n", argv[0]);
-
-       for (i = 1; i < argc; ++i) {
-               if (!strcmp(argv[i], "--"))
-                       break;
-               if (bases_count < sizeof(bases)/sizeof(*bases))
-                       bases[bases_count++] = argv[i];
-       }
-       if (argc - i != 3) /* "--" "<head>" "<remote>" */
-               die("Not handling anything other than two heads merge.");
-       if (verbosity >= 5)
-               buffer_output = 0;
-
-       branch1 = argv[++i];
-       branch2 = argv[++i];
-
-       h1 = get_ref(branch1);
-       h2 = get_ref(branch2);
-
-       branch1 = better_branch_name(branch1);
-       branch2 = better_branch_name(branch2);
-
-       if (show(3))
-               printf("Merging %s with %s\n", branch1, branch2);
-
-       index_fd = hold_locked_index(lock, 1);
-
-       for (i = 0; i < bases_count; i++) {
-               struct commit *ancestor = get_ref(bases[i]);
-               ca = commit_list_insert(ancestor, &ca);
-       }
-       clean = merge(h1, h2, branch1, branch2, ca, &result);
-
-       if (active_cache_changed &&
-           (write_cache(index_fd, active_cache, active_nr) ||
-            close(index_fd) || commit_locked_index(lock)))
-                       die ("unable to write %s", get_index_file());
-
-       return clean ? 0: 1;
+               o->verbosity =
+                       strtol(getenv("GIT_MERGE_VERBOSITY"), NULL, 10);
+       if (o->verbosity >= 5)
+               o->buffer_output = 0;
+       strbuf_init(&o->obuf, 0);
+       memset(&o->current_file_set, 0, sizeof(struct string_list));
+       o->current_file_set.strdup_strings = 1;
+       memset(&o->current_directory_set, 0, sizeof(struct string_list));
+       o->current_directory_set.strdup_strings = 1;
 }