Build-in merge-recursive

This makes write_tree_from_memory(), which writes the active cache as
a tree and returns the struct tree for it, available to other code. It
also makes available merge_trees(), which does the internal merge of
two trees with a known base, and merge_recursive(), which does the
recursive internal merge of two commits with a list of common
ancestors.

The first two of these will be used by checkout -m, and the third is
presumably useful in general, although the implementation of checkout
-m which entirely matches the behavior of the shell version does not
use it (since it ignores the difference of ancestry between the old
branch and the new branch).

Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>

1 files changed, 1762 insertions, 0 deletions

diff --git a/builtin-merge-recursive.c b/builtin-merge-recursive.c
new file mode 100644
index 000000000..45d460153
--- /dev/null
+++ b/builtin-merge-recursive.c
@@ -0,0 +1,1762 @@
+/*
+ * 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"
+#include "run-command.h"
+#include "tag.h"
+#include "unpack-trees.h"
+#include "path-list.h"
+#include "xdiff-interface.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;
+}
+
+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;
+}
+
+struct tree *write_tree_from_memory(void)
+{
+	struct tree *result = NULL;
+
+	if (unmerged_index()) {
+		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;
+}
+
+/*
+ * 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)
+{
+	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(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);
+
+	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 = ll_merge(&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_index()) {
+		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->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;
+}