Merge branch 'jc/cherry-pick' (early part)

* 'jc/cherry-pick' (early part):
  expose a helper function peel_to_type().
  merge-recursive: split low-level merge functions out.

Conflicts:

	Makefile
	builtin-merge-recursive.c
	sha1_name.c

diff --cc Makefile
index 7fbb81578264e47c83857e864e58b32c4f81a5fa,64f67afb8d107a9a1141f2c4fced9bf680fc4251..514738046f94abc9ab16bfebc3b0d3e0118b5a5f
--- 1/Makefile
--- 2/Makefile
+++ b/Makefile
@@@ -308,8 -301,7 +308,8 @@@ LIB_H = 
        run-command.h strbuf.h tag.h tree.h git-compat-util.h revision.h \
        tree-walk.h log-tree.h dir.h path-list.h unpack-trees.h builtin.h \
        utf8.h reflog-walk.h patch-ids.h attr.h decorate.h progress.h \
-       mailmap.h remote.h parse-options.h transport.h diffcore.h hash.h fsck.h \
 -      mailmap.h remote.h parse-options.h transport.h diffcore.h hash.h ll-merge.h
++      mailmap.h remote.h parse-options.h transport.h diffcore.h hash.h ll-merge.h fsck.h \
 +      pack-revindex.h
  
  DIFF_OBJS = \
        diff.o diff-lib.o diffcore-break.o diffcore-order.o \
@@@ -332,8 -324,7 +332,8 @@@ LIB_OBJS = 
        alloc.o merge-file.o path-list.o help.o unpack-trees.o $(DIFF_OBJS) \
        color.o wt-status.o archive-zip.o archive-tar.o shallow.o utf8.o \
        convert.o attr.o decorate.o progress.o mailmap.o symlinks.o remote.o \
 -      transport.o bundle.o walker.o parse-options.o ws.o archive.o ll-merge.o
 +      transport.o bundle.o walker.o parse-options.o ws.o archive.o branch.o \
-       alias.o fsck.o pack-revindex.o
++      ll-merge.o alias.o fsck.o pack-revindex.o
  
  BUILTIN_OBJS = \
        builtin-add.o \

diff --cc builtin-merge-recursive.c
index 6fe4102c0cfb29031f7fdce68ca4d1937e2fefd7,0000000000000000000000000000000000000000..5a0a7b529765fa229318af86a68e58a92e287154
mode 100644,000000..100644
--- 1/builtin-merge-recursive.c
--- /dev/null
+++ b/builtin-merge-recursive.c
@@@ -1,1754 -1,0 +1,1401 @@@
- #include "run-command.h"
 +/*
 + * Recursive Merge algorithm stolen from git-merge-recursive.py by
 + * Fredrik Kuivinen.
 + * The thieves were Alex Riesen and Johannes Schindelin, in June/July 2006
 + */
 +#include "cache.h"
 +#include "cache-tree.h"
 +#include "commit.h"
 +#include "blob.h"
 +#include "builtin.h"
 +#include "tree-walk.h"
 +#include "diff.h"
 +#include "diffcore.h"
- /*
-  * 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)
-                       return config_error_nonbool(var);
-               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 config_error_nonbool(var);
-               fn->description = strdup(value);
-               return 0;
-       }
- 
-       if (!strcmp("driver", ep)) {
-               if (!value)
-                       return config_error_nonbool(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 config_error_nonbool(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)
 +#include "tag.h"
 +#include "unpack-trees.h"
 +#include "path-list.h"
 +#include "xdiff-interface.h"
++#include "ll-merge.h"
 +#include "interpolate.h"
 +#include "attr.h"
 +#include "merge-recursive.h"
 +
 +static int subtree_merge;
 +
 +static struct tree *shift_tree_object(struct tree *one, struct tree *two)
 +{
 +      unsigned char shifted[20];
 +
 +      /*
 +       * NEEDSWORK: this limits the recursion depth to hardcoded
 +       * value '2' to avoid excessive overhead.
 +       */
 +      shift_tree(one->object.sha1, two->object.sha1, shifted, 2);
 +      if (!hashcmp(two->object.sha1, shifted))
 +              return two;
 +      return lookup_tree(shifted);
 +}
 +
 +/*
 + * A virtual commit has
 + * - (const char *)commit->util set to the name, and
 + * - *(int *)commit->object.sha1 set to the virtual id.
 + */
 +
 +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 *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;
 +}
 +
 +/*
 + * Since we use get_tree_entry(), which does not put the read object into
 + * the object pool, we cannot rely on a == b.
 + */
 +static int sha_eq(const unsigned char *a, const unsigned char *b)
 +{
 +      if (!a && !b)
 +              return 2;
 +      return a && b && hashcmp(a, b) == 0;
 +}
 +
 +/*
 + * Since we want to write the index eventually, we cannot reuse the index
 + * for these (temporary) data.
 + */
 +struct stage_data
 +{
 +      struct
 +      {
 +              unsigned mode;
 +              unsigned char sha[20];
 +      } stages[4];
 +      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)
 +{
 +      return (!call_depth && verbosity >= v) || verbosity >= 5;
 +}
 +
 +static void flush_output(void)
 +{
 +      if (obuf.len) {
 +              fputs(obuf.buf, stdout);
 +              strbuf_reset(&obuf);
 +      }
 +}
 +
 +static void output(int v, const char *fmt, ...)
 +{
 +      int len;
 +      va_list ap;
 +
 +      if (!show(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);
 +
 +      va_start(ap, fmt);
 +      len = vsnprintf(obuf.buf + obuf.len, strbuf_avail(&obuf), fmt, ap);
 +      va_end(ap);
 +
 +      if (len < 0)
 +              len = 0;
 +      if (len >= strbuf_avail(&obuf)) {
 +              strbuf_grow(&obuf, len + 2);
 +              va_start(ap, fmt);
 +              len = vsnprintf(obuf.buf + obuf.len, strbuf_avail(&obuf), fmt, ap);
 +              va_end(ap);
 +              if (len >= strbuf_avail(&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();
 +}
 +
 +static void output_commit_title(struct commit *commit)
 +{
 +      int i;
 +      flush_output();
 +      for (i = call_depth; i--;)
 +              fputs("  ", stdout);
 +      if (commit->util)
 +              printf("virtual %s\n", (char *)commit->util);
 +      else {
 +              printf("%s ", find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
 +              if (parse_commit(commit) != 0)
 +                      printf("(bad commit)\n");
 +              else {
 +                      const char *s;
 +                      int len;
 +                      for (s = commit->buffer; *s; s++)
 +                              if (*s == '\n' && s[1] == '\n') {
 +                                      s += 2;
 +                                      break;
 +                              }
 +                      for (len = 0; s[len] && '\n' != s[len]; len++)
 +                              ; /* do nothing */
 +                      printf("%.*s\n", len, s);
 +              }
 +      }
 +}
 +
 +static int add_cacheinfo(unsigned int mode, const unsigned char *sha1,
 +              const char *path, int stage, int refresh, int options)
 +{
 +      struct cache_entry *ce;
 +      ce = make_cache_entry(mode, sha1 ? sha1 : null_sha1, path, stage, refresh);
 +      if (!ce)
 +              return error("addinfo_cache failed for path '%s'", path);
 +      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);
 +      init_tree_desc(desc, tree->buffer, tree->size);
 +}
 +
 +static int git_merge_trees(int index_only,
 +                         struct tree *common,
 +                         struct tree *head,
 +                         struct tree *merge)
 +{
 +      int rc;
 +      struct tree_desc t[3];
 +      struct unpack_trees_options opts;
 +
 +      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;
 +
 +      init_tree_desc_from_tree(t+0, common);
 +      init_tree_desc_from_tree(t+1, head);
 +      init_tree_desc_from_tree(t+2, merge);
 +
 +      rc = unpack_trees(3, t, &opts);
 +      cache_tree_free(&active_cache_tree);
 +      return rc;
 +}
 +
 +struct tree *write_tree_from_memory(void)
 +{
 +      struct tree *result = NULL;
 +
 +      if (unmerged_cache()) {
 +              int i;
 +              output(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);
 +              }
 +              return NULL;
 +      }
 +
 +      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);
 +
 +      return result;
 +}
 +
 +static int save_files_dirs(const unsigned char *sha1,
 +              const char *base, int baselen, const char *path,
 +              unsigned int mode, int stage)
 +{
 +      int len = strlen(path);
 +      char *newpath = xmalloc(baselen + len + 1);
 +      memcpy(newpath, base, baselen);
 +      memcpy(newpath + baselen, path, len);
 +      newpath[baselen + len] = '\0';
 +
 +      if (S_ISDIR(mode))
 +              path_list_insert(newpath, &current_directory_set);
 +      else
 +              path_list_insert(newpath, &current_file_set);
 +      free(newpath);
 +
 +      return READ_TREE_RECURSIVE;
 +}
 +
 +static int get_files_dirs(struct tree *tree)
 +{
 +      int n;
 +      if (read_tree_recursive(tree, "", 0, 0, NULL, save_files_dirs) != 0)
 +              return 0;
 +      n = current_file_set.nr + current_directory_set.nr;
 +      return n;
 +}
 +
 +/*
 + * 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 path_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);
 +      get_tree_entry(a->object.sha1, 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->util = e;
 +      return e;
 +}
 +
 +/*
 + * 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)
 +{
 +      struct path_list *unmerged = xcalloc(1, sizeof(struct path_list));
 +      int i;
 +
 +      unmerged->strdup_paths = 1;
 +
 +      for (i = 0; i < active_nr; i++) {
 +              struct path_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);
 +              if (!item) {
 +                      item = path_list_insert(ce->name, unmerged);
 +                      item->util = xcalloc(1, sizeof(struct stage_data));
 +              }
 +              e = item->util;
 +              e->stages[ce_stage(ce)].mode = ce->ce_mode;
 +              hashcpy(e->stages[ce_stage(ce)].sha, ce->sha1);
 +      }
 +
 +      return unmerged;
 +}
 +
 +struct rename
 +{
 +      struct diff_filepair *pair;
 +      struct stage_data *src_entry;
 +      struct stage_data *dst_entry;
 +      unsigned processed:1;
 +};
 +
 +/*
 + * Get information of all renames which occurred between 'o_tree' and
 + * 'tree'. We need the three trees in the merge ('o_tree', 'a_tree' and
 + * 'b_tree') to be able to associate the correct cache entries with
 + * the rename information. 'tree' is always equal to either a_tree or b_tree.
 + */
 +static struct path_list *get_renames(struct tree *tree,
 +                                      struct tree *o_tree,
 +                                      struct tree *a_tree,
 +                                      struct tree *b_tree,
 +                                      struct path_list *entries)
 +{
 +      int i;
 +      struct path_list *renames;
 +      struct diff_options opts;
 +
 +      renames = xcalloc(1, sizeof(struct path_list));
 +      diff_setup(&opts);
 +      DIFF_OPT_SET(&opts, RECURSIVE);
 +      opts.detect_rename = DIFF_DETECT_RENAME;
 +      opts.rename_limit = rename_limit;
 +      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 rename *re;
 +              struct diff_filepair *pair = diff_queued_diff.queue[i];
 +              if (pair->status != 'R') {
 +                      diff_free_filepair(pair);
 +                      continue;
 +              }
 +              re = xmalloc(sizeof(*re));
 +              re->processed = 0;
 +              re->pair = pair;
 +              item = path_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);
 +              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->util = re;
 +      }
 +      opts.output_format = DIFF_FORMAT_NO_OUTPUT;
 +      diff_queued_diff.nr = 0;
 +      diff_flush(&opts);
 +      return renames;
 +}
 +
 +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)
 +              if (remove_file_from_cache(path))
 +                      return -1;
 +      if (o)
 +              if (add_cacheinfo(o->mode, o->sha1, path, 1, 0, options))
 +                      return -1;
 +      if (a)
 +              if (add_cacheinfo(a->mode, a->sha1, path, 2, 0, options))
 +                      return -1;
 +      if (b)
 +              if (add_cacheinfo(b->mode, b->sha1, path, 3, 0, options))
 +                      return -1;
 +      return 0;
 +}
 +
 +static int remove_path(const char *name)
 +{
 +      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;
 +
 +      if (update_cache) {
 +              if (remove_file_from_cache(path))
 +                      return -1;
 +      }
 +      if (update_working_directory) {
 +              unlink(path);
 +              if (errno != ENOENT || errno != EISDIR)
 +                      return -1;
 +              remove_path(path);
 +      }
 +      return 0;
 +}
 +
 +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(path);
 +      strcpy(newpath, path);
 +      *(p++) = '~';
 +      strcpy(p, branch);
 +      for (; *p; ++p)
 +              if ('/' == *p)
 +                      *p = '_';
 +      while (path_list_has_path(&current_file_set, newpath) ||
 +             path_list_has_path(&current_directory_set, newpath) ||
 +             lstat(newpath, &st) == 0)
 +              sprintf(p, "_%d", suffix++);
 +
 +      path_list_insert(newpath, &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) {
 +              long ret = write_in_full(fd, buf, size);
 +              if (ret < 0) {
 +                      /* Ignore epipe */
 +                      if (errno == EPIPE)
 +                              break;
 +                      die("merge-recursive: %s", strerror(errno));
 +              } else if (!ret) {
 +                      die("merge-recursive: disk full?");
 +              }
 +              size -= ret;
 +              buf += ret;
 +      }
 +}
 +
 +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);
 +      if (status) {
 +              if (status == -3) {
 +                      /* something else exists */
 +                      error(msg, path, ": perhaps a D/F conflict?");
 +                      return -1;
 +              }
 +              die(msg, path, "");
 +      }
 +
 +      /* Successful unlink is good.. */
 +      if (!unlink(path))
 +              return 0;
 +      /* .. and so is no existing file */
 +      if (errno == ENOENT)
 +              return 0;
 +      /* .. but not some other error (who really cares what?) */
 +      return error(msg, path, ": perhaps a D/F conflict?");
 +}
 +
 +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;
 +
 +      if (update_wd) {
 +              enum object_type type;
 +              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 (make_room_for_path(path) < 0) {
 +                      update_wd = 0;
 +                      goto update_index;
 +              }
 +              if (S_ISREG(mode) || (!has_symlinks && S_ISLNK(mode))) {
 +                      int fd;
 +                      if (mode & 0100)
 +                              mode = 0777;
 +                      else
 +                              mode = 0666;
 +                      fd = open(path, O_WRONLY | O_TRUNC | O_CREAT, mode);
 +                      if (fd < 0)
 +                              die("failed to open %s: %s", path, strerror(errno));
 +                      flush_buffer(fd, buf, size);
 +                      close(fd);
 +              } else if (S_ISLNK(mode)) {
 +                      char *lnk = xmemdupz(buf, size);
 +                      mkdir_p(path, 0777);
 +                      unlink(path);
 +                      symlink(lnk, path);
 +                      free(lnk);
 +              } else
 +                      die("do not know what to do with %06o %s '%s'",
 +                          mode, sha1_to_hex(sha), path);
 +      }
 + update_index:
 +      if (update_cache)
 +              add_cacheinfo(mode, sha, path, 0, update_wd, ADD_CACHE_OK_TO_ADD);
 +}
 +
 +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);
 +}
 +
 +/* Low level file merging, update and removal */
 +
 +struct merge_file_info
 +{
 +      unsigned char sha[20];
 +      unsigned mode;
 +      unsigned clean:1,
 +               merge:1;
 +};
 +
 +static void fill_mm(const unsigned char *sha1, mmfile_t *mm)
 +{
 +      unsigned long size;
 +      enum object_type type;
 +
 +      if (!hashcmp(sha1, null_sha1)) {
 +              mm->ptr = xstrdup("");
 +              mm->size = 0;
 +              return;
 +      }
 +
 +      mm->ptr = read_sha1_file(sha1, &type, &size);
 +      if (!mm->ptr || type != OBJ_BLOB)
 +              die("unable to read blob object %s", sha1_to_hex(sha1));
 +      mm->size = size;
 +}
 +
-       const char *ll_driver_name;
-       const struct ll_merge_driver *driver;
++static int merge_3way(mmbuffer_t *result_buf,
++                    struct diff_filespec *o,
++                    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;
-       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);
 +
 +      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);
 +
-                       merge_status = ll_merge(&result_buf, o, a, b,
-                                               branch1, branch2);
++      merge_status = ll_merge(result_buf, a->path, &orig,
++                              &src1, name1, &src2, name2,
++                              index_only);
 +
 +      free(name1);
 +      free(name2);
 +      free(orig.ptr);
 +      free(src1.ptr);
 +      free(src2.ptr);
 +      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)
 +{
 +      struct merge_file_info result;
 +      result.merge = 0;
 +      result.clean = 1;
 +
 +      if ((S_IFMT & a->mode) != (S_IFMT & b->mode)) {
 +              result.clean = 0;
 +              if (S_ISREG(a->mode)) {
 +                      result.mode = a->mode;
 +                      hashcpy(result.sha, a->sha1);
 +              } else {
 +                      result.mode = b->mode;
 +                      hashcpy(result.sha, b->sha1);
 +              }
 +      } else {
 +              if (!sha_eq(a->sha1, o->sha1) && !sha_eq(b->sha1, o->sha1))
 +                      result.merge = 1;
 +
 +              result.mode = a->mode == o->mode ? b->mode: a->mode;
 +
 +              if (sha_eq(a->sha1, o->sha1))
 +                      hashcpy(result.sha, b->sha1);
 +              else if (sha_eq(b->sha1, o->sha1))
 +                      hashcpy(result.sha, a->sha1);
 +              else if (S_ISREG(a->mode)) {
 +                      mmbuffer_t result_buf;
 +                      int merge_status;
 +
++                      merge_status = merge_3way(&result_buf, o, a, b,
++                                                branch1, branch2);
 +
 +                      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_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,
 +                                 const char *branch1,
 +                                 struct rename *ren2,
 +                                 const char *branch2)
 +{
 +      char *del[2];
 +      int delp = 0;
 +      const char *ren1_dst = ren1->pair->two->path;
 +      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",
 +                     ren1_dst, branch2, dst_name1);
 +              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(1, "%s is a directory in %s added as %s instead",
 +                     ren2_dst, branch1, dst_name2);
 +              remove_file(0, ren2_dst, 0);
 +      }
 +      if (index_only) {
 +              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);
 +               */
 +      } else {
 +              update_stages(dst_name1, NULL, ren1->pair->two, NULL, 1);
 +              update_stages(dst_name2, NULL, NULL, ren2->pair->two, 1);
 +      }
 +      while (delp--)
 +              free(del[delp]);
 +}
 +
 +static void conflict_rename_dir(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);
 +      free(new_path);
 +}
 +
 +static void conflict_rename_rename_2(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",
 +             ren1->pair->one->path, new_path1,
 +             ren2->pair->one->path, new_path2);
 +      remove_file(0, ren1->pair->two->path, 0);
 +      update_file(0, ren1->pair->two->sha1, ren1->pair->two->mode, new_path1);
 +      update_file(0, ren2->pair->two->sha1, ren2->pair->two->mode, new_path2);
 +      free(new_path2);
 +      free(new_path1);
 +}
 +
 +static int process_renames(struct path_list *a_renames,
 +                         struct path_list *b_renames,
 +                         const char *a_branch,
 +                         const char *b_branch)
 +{
 +      int clean_merge = 1, i, j;
 +      struct path_list a_by_dst = {NULL, 0, 0, 0}, b_by_dst = {NULL, 0, 0, 0};
 +      const struct rename *sre;
 +
 +      for (i = 0; i < a_renames->nr; i++) {
 +              sre = a_renames->items[i].util;
 +              path_list_insert(sre->pair->two->path, &a_by_dst)->util
 +                      = sre->dst_entry;
 +      }
 +      for (i = 0; i < b_renames->nr; i++) {
 +              sre = b_renames->items[i].util;
 +              path_list_insert(sre->pair->two->path, &b_by_dst)->util
 +                      = sre->dst_entry;
 +      }
 +
 +      for (i = 0, j = 0; i < a_renames->nr || j < b_renames->nr;) {
 +              int compare;
 +              char *src;
 +              struct path_list *renames1, *renames2, *renames2Dst;
 +              struct rename *ren1 = NULL, *ren2 = NULL;
 +              const char *branch1, *branch2;
 +              const char *ren1_src, *ren1_dst;
 +
 +              if (i >= a_renames->nr) {
 +                      compare = 1;
 +                      ren2 = b_renames->items[j++].util;
 +              } else if (j >= b_renames->nr) {
 +                      compare = -1;
 +                      ren1 = a_renames->items[i++].util;
 +              } else {
 +                      compare = strcmp(a_renames->items[i].path,
 +                                      b_renames->items[j].path);
 +                      if (compare <= 0)
 +                              ren1 = a_renames->items[i++].util;
 +                      if (compare >= 0)
 +                              ren2 = b_renames->items[j++].util;
 +              }
 +
 +              /* TODO: refactor, so that 1/2 are not needed */
 +              if (ren1) {
 +                      renames1 = a_renames;
 +                      renames2 = b_renames;
 +                      renames2Dst = &b_by_dst;
 +                      branch1 = a_branch;
 +                      branch2 = b_branch;
 +              } else {
 +                      struct rename *tmp;
 +                      renames1 = b_renames;
 +                      renames2 = a_renames;
 +                      renames2Dst = &a_by_dst;
 +                      branch1 = b_branch;
 +                      branch2 = a_branch;
 +                      tmp = ren2;
 +                      ren2 = ren1;
 +                      ren1 = tmp;
 +              }
 +              src = ren1->pair->one->path;
 +
 +              ren1->dst_entry->processed = 1;
 +              ren1->src_entry->processed = 1;
 +
 +              if (ren1->processed)
 +                      continue;
 +              ren1->processed = 1;
 +
 +              ren1_src = ren1->pair->one->path;
 +              ren1_dst = ren1->pair->two->path;
 +
 +              if (ren2) {
 +                      const char *ren2_src = ren2->pair->one->path;
 +                      const char *ren2_dst = ren2->pair->two->path;
 +                      /* Renamed in 1 and renamed in 2 */
 +                      if (strcmp(ren1_src, ren2_src) != 0)
 +                              die("ren1.src != ren2.src");
 +                      ren2->dst_entry->processed = 1;
 +                      ren2->processed = 1;
 +                      if (strcmp(ren1_dst, ren2_dst) != 0) {
 +                              clean_merge = 0;
 +                              output(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) {
 +                                      remove_file_from_cache(src);
 +                                      update_file(0, ren1->pair->one->sha1,
 +                                                  ren1->pair->one->mode, src);
 +                              }
 +                              conflict_rename_rename(ren1, branch1, ren2, branch2);
 +                      } else {
 +                              struct merge_file_info mfi;
 +                              remove_file(1, ren1_src, 1);
 +                              mfi = merge_file(ren1->pair->one,
 +                                               ren1->pair->two,
 +                                               ren2->pair->two,
 +                                               branch1,
 +                                               branch2);
 +                              if (mfi.merge || !mfi.clean)
 +                                      output(1, "Renamed %s->%s", src, ren1_dst);
 +
 +                              if (mfi.merge)
 +                                      output(2, "Auto-merged %s", ren1_dst);
 +
 +                              if (!mfi.clean) {
 +                                      output(1, "CONFLICT (content): merge conflict in %s",
 +                                             ren1_dst);
 +                                      clean_merge = 0;
 +
 +                                      if (!index_only)
 +                                              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);
 +                      }
 +              } else {
 +                      /* Renamed in 1, maybe changed in 2 */
 +                      struct path_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);
 +
 +                      hashcpy(src_other.sha1, ren1->src_entry->stages[stage].sha);
 +                      src_other.mode = ren1->src_entry->stages[stage].mode;
 +                      hashcpy(dst_other.sha1, ren1->dst_entry->stages[stage].sha);
 +                      dst_other.mode = ren1->dst_entry->stages[stage].mode;
 +
 +                      try_merge = 0;
 +
 +                      if (path_list_has_path(&current_directory_set, ren1_dst)) {
 +                              clean_merge = 0;
 +                              output(1, "CONFLICT (rename/directory): Renamed %s->%s in %s "
 +                                     " directory %s added in %s",
 +                                     ren1_src, ren1_dst, branch1,
 +                                     ren1_dst, branch2);
 +                              conflict_rename_dir(ren1, branch1);
 +                      } else if (sha_eq(src_other.sha1, null_sha1)) {
 +                              clean_merge = 0;
 +                              output(1, "CONFLICT (rename/delete): Renamed %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);
 +                      } 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. "
 +                                     "%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))) {
 +                              ren2 = item->util;
 +                              clean_merge = 0;
 +                              ren2->processed = 1;
 +                              output(1, "CONFLICT (rename/rename): Renamed %s->%s in %s. "
 +                                     "Renamed %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);
 +                      } else
 +                              try_merge = 1;
 +
 +                      if (try_merge) {
 +                              struct diff_filespec *o, *a, *b;
 +                              struct merge_file_info mfi;
 +                              src_other.path = (char *)ren1_src;
 +
 +                              o = ren1->pair->one;
 +                              if (a_renames == renames1) {
 +                                      a = ren1->pair->two;
 +                                      b = &src_other;
 +                              } else {
 +                                      b = ren1->pair->two;
 +                                      a = &src_other;
 +                              }
 +                              mfi = merge_file(o, a, b,
 +                                              a_branch, b_branch);
 +
 +                              if (mfi.clean &&
 +                                  sha_eq(mfi.sha, ren1->pair->two->sha1) &&
 +                                  mfi.mode == ren1->pair->two->mode)
 +                                      /*
 +                                       * This messaged is part of
 +                                       * t6022 test. If you change
 +                                       * it update the test too.
 +                                       */
 +                                      output(3, "Skipped %s (merged same as existing)", ren1_dst);
 +                              else {
 +                                      if (mfi.merge || !mfi.clean)
 +                                              output(1, "Renamed %s => %s", ren1_src, ren1_dst);
 +                                      if (mfi.merge)
 +                                              output(2, "Auto-merged %s", ren1_dst);
 +                                      if (!mfi.clean) {
 +                                              output(1, "CONFLICT (rename/modify): Merge conflict in %s",
 +                                                     ren1_dst);
 +                                              clean_merge = 0;
 +
 +                                              if (!index_only)
 +                                                      update_stages(ren1_dst,
 +                                                                    o, a, b, 1);
 +                                      }
 +                                      update_file(mfi.clean, mfi.sha, mfi.mode, ren1_dst);
 +                              }
 +                      }
 +              }
 +      }
 +      path_list_clear(&a_by_dst, 0);
 +      path_list_clear(&b_by_dst, 0);
 +
 +      return clean_merge;
 +}
 +
 +static unsigned char *stage_sha(const unsigned char *sha, unsigned mode)
 +{
 +      return (is_null_sha1(sha) || mode == 0) ? NULL: (unsigned char *)sha;
 +}
 +
 +/* Per entry merge function */
 +static int process_entry(const char *path, struct stage_data *entry,
 +                       const char *branch1,
 +                       const char *branch2)
 +{
 +      /*
 +      printf("processing entry, clean cache: %s\n", index_only ? "yes": "no");
 +      print_index_entry("\tpath: ", entry);
 +      */
 +      int clean_merge = 1;
 +      unsigned o_mode = entry->stages[1].mode;
 +      unsigned a_mode = entry->stages[2].mode;
 +      unsigned b_mode = entry->stages[3].mode;
 +      unsigned char *o_sha = stage_sha(entry->stages[1].sha, o_mode);
 +      unsigned char *a_sha = stage_sha(entry->stages[2].sha, a_mode);
 +      unsigned char *b_sha = stage_sha(entry->stages[3].sha, b_mode);
 +
 +      if (o_sha && (!a_sha || !b_sha)) {
 +              /* Case A: Deleted in one */
 +              if ((!a_sha && !b_sha) ||
 +                  (sha_eq(a_sha, o_sha) && !b_sha) ||
 +                  (!a_sha && sha_eq(b_sha, o_sha))) {
 +                      /* Deleted in both or deleted in one and
 +                       * unchanged in the other */
 +                      if (a_sha)
 +                              output(2, "Removed %s", 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;
 +                      if (!a_sha) {
 +                              output(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);
 +                      } else {
 +                              output(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);
 +                      }
 +              }
 +
 +      } else if ((!o_sha && a_sha && !b_sha) ||
 +                 (!o_sha && !a_sha && b_sha)) {
 +              /* Case B: Added in one. */
 +              const char *add_branch;
 +              const char *other_branch;
 +              unsigned mode;
 +              const unsigned char *sha;
 +              const char *conf;
 +
 +              if (a_sha) {
 +                      add_branch = branch1;
 +                      other_branch = branch2;
 +                      mode = a_mode;
 +                      sha = a_sha;
 +                      conf = "file/directory";
 +              } else {
 +                      add_branch = branch2;
 +                      other_branch = 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);
 +                      clean_merge = 0;
 +                      output(1, "CONFLICT (%s): There is a directory with name %s in %s. "
 +                             "Added %s as %s",
 +                             conf, path, other_branch, path, new_path);
 +                      remove_file(0, path, 0);
 +                      update_file(0, sha, mode, new_path);
 +              } else {
 +                      output(2, "Added %s", path);
 +                      update_file(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;
 +
 +              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;
 +              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);
 +
 +              clean_merge = mfi.clean;
 +              if (mfi.clean)
 +                      update_file(1, mfi.sha, mfi.mode, path);
 +              else if (S_ISGITLINK(mfi.mode))
 +                      output(1, "CONFLICT (submodule): Merge conflict in %s "
 +                             "- needs %s", path, sha1_to_hex(b.sha1));
 +              else {
 +                      output(1, "CONFLICT (%s): Merge conflict in %s",
 +                                      reason, path);
 +
 +                      if (index_only)
 +                              update_file(0, mfi.sha, mfi.mode, path);
 +                      else
 +                              update_file_flags(mfi.sha, mfi.mode, path,
 +                                            0 /* update_cache */, 1 /* update_working_directory */);
 +              }
 +      } else if (!o_sha && !a_sha && !b_sha) {
 +              /*
 +               * 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);
 +      } else
 +              die("Fatal merge failure, shouldn't happen.");
 +
 +      return clean_merge;
 +}
 +
 +int merge_trees(struct tree *head,
 +              struct tree *merge,
 +              struct tree *common,
 +              const char *branch1,
 +              const char *branch2,
 +              struct tree **result)
 +{
 +      int code, clean;
 +
 +      if (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!");
 +              *result = head;
 +              return 1;
 +      }
 +
 +      code = git_merge_trees(index_only, 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_cache()) {
 +              struct path_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);
 +
 +              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);
 +              for (i = 0; i < entries->nr; i++) {
 +                      const char *path = entries->items[i].path;
 +                      struct stage_data *e = entries->items[i].util;
 +                      if (!e->processed
 +                              && !process_entry(path, e, branch1, branch2))
 +                              clean = 0;
 +              }
 +
 +              path_list_clear(re_merge, 0);
 +              path_list_clear(re_head, 0);
 +              path_list_clear(entries, 1);
 +
 +      }
 +      else
 +              clean = 1;
 +
 +      if (index_only)
 +              *result = write_tree_from_memory();
 +
 +      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 cleanness of the merge.
 + */
 +int merge_recursive(struct commit *h1,
 +                  struct commit *h2,
 +                  const char *branch1,
 +                  const char *branch2,
 +                  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 (!ca) {
 +              ca = get_merge_bases(h1, h2, 1);
 +              ca = reverse_commit_list(ca);
 +      }
 +
 +      if (show(5)) {
 +              output(5, "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;
 +              pretend_sha1_file(NULL, 0, OBJ_TREE, tree->object.sha1);
 +              merged_common_ancestors = make_virtual_commit(tree, "ancestor");
 +      }
 +
 +      for (iter = ca; iter; iter = iter->next) {
 +              call_depth++;
 +              /*
 +               * When the merge fails, the result contains files
 +               * with conflict markers. The cleanness flag is
 +               * ignored, it was never actually used, as result of
 +               * merge_trees has always overwritten it: the committed
 +               * "conflicts" were already resolved.
 +               */
 +              discard_cache();
 +              merge_recursive(merged_common_ancestors, iter->item,
 +                              "Temporary merge branch 1",
 +                              "Temporary merge branch 2",
 +                              NULL,
 +                              &merged_common_ancestors);
 +              call_depth--;
 +
 +              if (!merged_common_ancestors)
 +                      die("merge returned no commit");
 +      }
 +
 +      discard_cache();
 +      if (!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);
 +
 +      if (index_only) {
 +              *result = make_virtual_commit(mrtree, "merged tree");
 +              commit_list_insert(h1, &(*result)->parents);
 +              commit_list_insert(h2, &(*result)->parents->next);
 +      }
 +      flush_output();
 +      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)
 +{
 +      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));
 +      if (!object)
 +              return NULL;
 +      if (object->type == OBJ_TREE)
 +              return make_virtual_commit((struct tree*)object,
 +                      better_branch_name(ref));
 +      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 (struct commit *)object;
 +}
 +
 +static int merge_config(const char *var, const char *value)
 +{
 +      if (!strcasecmp(var, "merge.verbosity")) {
 +              verbosity = git_config_int(var, value);
 +              return 0;
 +      }
 +      if (!strcasecmp(var, "diff.renamelimit")) {
 +              rename_limit = git_config_int(var, value);
 +              return 0;
 +      }
 +      return git_default_config(var, value);
 +}
 +
 +int cmd_merge_recursive(int argc, const char **argv, const char *prefix)
 +{
 +      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);
 +      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_recursive(h1, h2, branch1, branch2, ca, &result);
 +
 +      if (active_cache_changed &&
 +          (write_cache(index_fd, active_cache, active_nr) ||
 +           commit_locked_index(lock)))
 +                      die ("unable to write %s", get_index_file());
 +
 +      return clean ? 0: 1;
 +}

diff --cc cache.h
Simple merge

diff --cc sha1_name.c
Simple merge