text: /*
   * 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 "advice.h"
  #include "lockfile.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 "tag.h"
  #include "unpack-trees.h"
  #include "string-list.h"
  #include "xdiff-interface.h"
  #include "ll-merge.h"
  #include "attr.h"
  #include "merge-recursive.h"
  #include "dir.h"
  #include "submodule.h"
  
  static struct tree *shift_tree_object(struct tree *one, struct tree *two,
  				      const char *subtree_shift)
  {
  	unsigned char shifted[20];
  
  	if (!*subtree_shift) {
  		shift_tree(one->object.sha1, two->object.sha1, shifted, 0);
  	} else {
  		shift_tree_by(one->object.sha1, two->object.sha1, shifted,
  			      subtree_shift);
  	}
  	if (!hashcmp(two->object.sha1, shifted))
  		return two;
  	return lookup_tree(shifted);
  }
  
  static struct commit *make_virtual_commit(struct tree *tree, const char *comment)
  {
  	struct commit *commit = alloc_commit_node();
  	struct merge_remote_desc *desc = xmalloc(sizeof(*desc));
  
  	desc->name = comment;
  	desc->obj = (struct object *)commit;
  	commit->tree = tree;
  	commit->util = desc;
  	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;
  }
  
  enum rename_type {
  	RENAME_NORMAL = 0,
  	RENAME_DELETE,
  	RENAME_ONE_FILE_TO_ONE,
  	RENAME_ONE_FILE_TO_TWO,
  	RENAME_TWO_FILES_TO_ONE
  };
  
  struct rename_conflict_info {
  	enum rename_type rename_type;
  	struct diff_filepair *pair1;
  	struct diff_filepair *pair2;
  	const char *branch1;
  	const char *branch2;
  	struct stage_data *dst_entry1;
  	struct stage_data *dst_entry2;
  	struct diff_filespec ren1_other;
  	struct diff_filespec ren2_other;
  };
  
  /*
   * 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];
  	struct rename_conflict_info *rename_conflict_info;
  	unsigned processed:1;
  };
  
  static inline void setup_rename_conflict_info(enum rename_type rename_type,
  					      struct diff_filepair *pair1,
  					      struct diff_filepair *pair2,
  					      const char *branch1,
  					      const char *branch2,
  					      struct stage_data *dst_entry1,
  					      struct stage_data *dst_entry2,
  					      struct merge_options *o,
  					      struct stage_data *src_entry1,
  					      struct stage_data *src_entry2)
  {
  	struct rename_conflict_info *ci = xcalloc(1, sizeof(struct rename_conflict_info));
  	ci->rename_type = rename_type;
  	ci->pair1 = pair1;
  	ci->branch1 = branch1;
  	ci->branch2 = branch2;
  
  	ci->dst_entry1 = dst_entry1;
  	dst_entry1->rename_conflict_info = ci;
  	dst_entry1->processed = 0;
  
  	assert(!pair2 == !dst_entry2);
  	if (dst_entry2) {
  		ci->dst_entry2 = dst_entry2;
  		ci->pair2 = pair2;
  		dst_entry2->rename_conflict_info = ci;
  	}
  
  	if (rename_type == RENAME_TWO_FILES_TO_ONE) {
  		/*
  		 * For each rename, there could have been
  		 * modifications on the side of history where that
  		 * file was not renamed.
  		 */
  		int ostage1 = o->branch1 == branch1 ? 3 : 2;
  		int ostage2 = ostage1 ^ 1;
  
  		ci->ren1_other.path = pair1->one->path;
  		hashcpy(ci->ren1_other.sha1, src_entry1->stages[ostage1].sha);
  		ci->ren1_other.mode = src_entry1->stages[ostage1].mode;
  
  		ci->ren2_other.path = pair2->one->path;
  		hashcpy(ci->ren2_other.sha1, src_entry2->stages[ostage2].sha);
  		ci->ren2_other.mode = src_entry2->stages[ostage2].mode;
  	}
  }
  
  static int show(struct merge_options *o, int v)
  {
  	return (!o->call_depth && o->verbosity >= v) || o->verbosity >= 5;
  }
  
  static void flush_output(struct merge_options *o)
  {
  	if (o->obuf.len) {
  		fputs(o->obuf.buf, stdout);
  		strbuf_reset(&o->obuf);
  	}
  }
  
  __attribute__((format (printf, 3, 4)))
  static void output(struct merge_options *o, int v, const char *fmt, ...)
  {
  	va_list ap;
  
  	if (!show(o, v))
  		return;
  
  	strbuf_addchars(&o->obuf, ' ', o->call_depth * 2);
  
  	va_start(ap, fmt);
  	strbuf_vaddf(&o->obuf, fmt, ap);
  	va_end(ap);
  
  	strbuf_addch(&o->obuf, '\n');
  	if (!o->buffer_output)
  		flush_output(o);
  }
  
  static void output_commit_title(struct merge_options *o, struct commit *commit)
  {
  	int i;
  	flush_output(o);
  	for (i = o->call_depth; i--;)
  		fputs("  ", stdout);
  	if (commit->util)
  		printf("virtual %s\n", merge_remote_util(commit)->name);
  	else {
  		printf("%s ", find_unique_abbrev(commit->object.sha1, DEFAULT_ABBREV));
  		if (parse_commit(commit) != 0)
  			printf(_("(bad commit)\n"));
  		else {
  			const char *title;
  			const char *msg = get_commit_buffer(commit, NULL);
  			int len = find_commit_subject(msg, &title);
  			if (len)
  				printf("%.*s\n", len, title);
  			unuse_commit_buffer(commit, msg);
  		}
  	}
  }
  
  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 ? (CE_MATCH_REFRESH |
  					  CE_MATCH_IGNORE_MISSING) : 0 ));
  	if (!ce)
  		return error(_("addinfo_cache failed for path '%s'"), path);
  	return add_cache_entry(ce, options);
  }
  
  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;
  	opts.src_index = &the_index;
  	opts.dst_index = &the_index;
  	setup_unpack_trees_porcelain(&opts, "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(struct merge_options *o)
  {
  	struct tree *result = NULL;
  
  	if (unmerged_cache()) {
  		int i;
  		fprintf(stderr, "BUG: There are unmerged index entries:\n");
  		for (i = 0; i < active_nr; i++) {
  			const struct cache_entry *ce = active_cache[i];
  			if (ce_stage(ce))
  				fprintf(stderr, "BUG: %d %.*s\n", ce_stage(ce),
  					(int)ce_namelen(ce), ce->name);
  		}
  		die("Bug in merge-recursive.c");
  	}
  
  	if (!active_cache_tree)
  		active_cache_tree = cache_tree();
  
  	if (!cache_tree_fully_valid(active_cache_tree) &&
  	    cache_tree_update(&the_index, 0) < 0)
  		die(_("error building trees"));
  
  	result = lookup_tree(active_cache_tree->sha1);
  
  	return result;
  }
  
  static int save_files_dirs(const unsigned char *sha1,
  		struct strbuf *base, const char *path,
  		unsigned int mode, int stage, void *context)
  {
  	int baselen = base->len;
  	struct merge_options *o = context;
  
  	strbuf_addstr(base, path);
  
  	if (S_ISDIR(mode))
  		string_list_insert(&o->current_directory_set, base->buf);
  	else
  		string_list_insert(&o->current_file_set, base->buf);
  
  	strbuf_setlen(base, baselen);
  	return (S_ISDIR(mode) ? READ_TREE_RECURSIVE : 0);
  }
  
  static int get_files_dirs(struct merge_options *o, struct tree *tree)
  {
  	int n;
  	struct pathspec match_all;
  	memset(&match_all, 0, sizeof(match_all));
  	if (read_tree_recursive(tree, "", 0, 0, &match_all, save_files_dirs, o))
  		return 0;
  	n = o->current_file_set.nr + o->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 string_list *entries)
  {
  	struct string_list_item *item;
  	struct stage_data *e = xcalloc(1, sizeof(struct stage_data));
  	get_tree_entry(o->object.sha1, path,
  			e->stages[1].sha, &e->stages[1].mode);
  	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 = string_list_insert(entries, path);
  	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 string_list *get_unmerged(void)
  {
  	struct string_list *unmerged = xcalloc(1, sizeof(struct string_list));
  	int i;
  
  	unmerged->strdup_strings = 1;
  
  	for (i = 0; i < active_nr; i++) {
  		struct string_list_item *item;
  		struct stage_data *e;
  		const struct cache_entry *ce = active_cache[i];
  		if (!ce_stage(ce))
  			continue;
  
  		item = string_list_lookup(unmerged, ce->name);
  		if (!item) {
  			item = string_list_insert(unmerged, ce->name);
  			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;
  }
  
  static int string_list_df_name_compare(const void *a, const void *b)
  {
  	const struct string_list_item *one = a;
  	const struct string_list_item *two = b;
  	int onelen = strlen(one->string);
  	int twolen = strlen(two->string);
  	/*
  	 * Here we only care that entries for D/F conflicts are
  	 * adjacent, in particular with the file of the D/F conflict
  	 * appearing before files below the corresponding directory.
  	 * The order of the rest of the list is irrelevant for us.
  	 *
  	 * To achieve this, we sort with df_name_compare and provide
  	 * the mode S_IFDIR so that D/F conflicts will sort correctly.
  	 * We use the mode S_IFDIR for everything else for simplicity,
  	 * since in other cases any changes in their order due to
  	 * sorting cause no problems for us.
  	 */
  	int cmp = df_name_compare(one->string, onelen, S_IFDIR,
  				  two->string, twolen, S_IFDIR);
  	/*
  	 * Now that 'foo' and 'foo/bar' compare equal, we have to make sure
  	 * that 'foo' comes before 'foo/bar'.
  	 */
  	if (cmp)
  		return cmp;
  	return onelen - twolen;
  }
  
  static void record_df_conflict_files(struct merge_options *o,
  				     struct string_list *entries)
  {
  	/* If there is a D/F conflict and the file for such a conflict
  	 * currently exist in the working tree, we want to allow it to be
  	 * removed to make room for the corresponding directory if needed.
  	 * The files underneath the directories of such D/F conflicts will
  	 * be processed before the corresponding file involved in the D/F
  	 * conflict.  If the D/F directory ends up being removed by the
  	 * merge, then we won't have to touch the D/F file.  If the D/F
  	 * directory needs to be written to the working copy, then the D/F
  	 * file will simply be removed (in make_room_for_path()) to make
  	 * room for the necessary paths.  Note that if both the directory
  	 * and the file need to be present, then the D/F file will be
  	 * reinstated with a new unique name at the time it is processed.
  	 */
  	struct string_list df_sorted_entries;
  	const char *last_file = NULL;
  	int last_len = 0;
  	int i;
  
  	/*
  	 * If we're merging merge-bases, we don't want to bother with
  	 * any working directory changes.
  	 */
  	if (o->call_depth)
  		return;
  
  	/* Ensure D/F conflicts are adjacent in the entries list. */
  	memset(&df_sorted_entries, 0, sizeof(struct string_list));
  	for (i = 0; i < entries->nr; i++) {
  		struct string_list_item *next = &entries->items[i];
  		string_list_append(&df_sorted_entries, next->string)->util =
  				   next->util;
  	}
  	qsort(df_sorted_entries.items, entries->nr, sizeof(*entries->items),
  	      string_list_df_name_compare);
  
  	string_list_clear(&o->df_conflict_file_set, 1);
  	for (i = 0; i < df_sorted_entries.nr; i++) {
  		const char *path = df_sorted_entries.items[i].string;
  		int len = strlen(path);
  		struct stage_data *e = df_sorted_entries.items[i].util;
  
  		/*
  		 * Check if last_file & path correspond to a D/F conflict;
  		 * i.e. whether path is last_file+'/'+<something>.
  		 * If so, record that it's okay to remove last_file to make
  		 * room for path and friends if needed.
  		 */
  		if (last_file &&
  		    len > last_len &&
  		    memcmp(path, last_file, last_len) == 0 &&
  		    path[last_len] == '/') {
  			string_list_insert(&o->df_conflict_file_set, last_file);
  		}
  
  		/*
  		 * Determine whether path could exist as a file in the
  		 * working directory as a possible D/F conflict.  This
  		 * will only occur when it exists in stage 2 as a
  		 * file.
  		 */
  		if (S_ISREG(e->stages[2].mode) || S_ISLNK(e->stages[2].mode)) {
  			last_file = path;
  			last_len = len;
  		} else {
  			last_file = NULL;
  		}
  	}
  	string_list_clear(&df_sorted_entries, 0);
  }
  
  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 string_list *get_renames(struct merge_options *o,
  				       struct tree *tree,
  				       struct tree *o_tree,
  				       struct tree *a_tree,
  				       struct tree *b_tree,
  				       struct string_list *entries)
  {
  	int i;
  	struct string_list *renames;
  	struct diff_options opts;
  
  	renames = xcalloc(1, sizeof(struct string_list));
  	diff_setup(&opts);
  	DIFF_OPT_SET(&opts, RECURSIVE);
  	DIFF_OPT_CLR(&opts, RENAME_EMPTY);
  	opts.detect_rename = DIFF_DETECT_RENAME;
  	opts.rename_limit = o->merge_rename_limit >= 0 ? o->merge_rename_limit :
  			    o->diff_rename_limit >= 0 ? o->diff_rename_limit :
  			    1000;
  	opts.rename_score = o->rename_score;
  	opts.show_rename_progress = o->show_rename_progress;
  	opts.output_format = DIFF_FORMAT_NO_OUTPUT;
  	diff_setup_done(&opts);
  	diff_tree_sha1(o_tree->object.sha1, tree->object.sha1, "", &opts);
  	diffcore_std(&opts);
  	if (opts.needed_rename_limit > o->needed_rename_limit)
  		o->needed_rename_limit = opts.needed_rename_limit;
  	for (i = 0; i < diff_queued_diff.nr; ++i) {
  		struct string_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 = string_list_lookup(entries, re->pair->one->path);
  		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 = string_list_lookup(entries, re->pair->two->path);
  		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 = string_list_insert(renames, pair->one->path);
  		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, const struct diff_filespec *o,
  			 const struct diff_filespec *a,
  			 const struct diff_filespec *b)
  {
  
  	/*
  	 * NOTE: It is usually a bad idea to call update_stages on a path
  	 * before calling update_file on that same path, since it can
  	 * sometimes lead to spurious "refusing to lose untracked file..."
  	 * messages from update_file (via make_room_for path via
  	 * would_lose_untracked).  Instead, reverse the order of the calls
  	 * (executing update_file first and then update_stages).
  	 */
  	int clear = 1;
  	int options = ADD_CACHE_OK_TO_ADD | ADD_CACHE_SKIP_DFCHECK;
  	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 void update_entry(struct stage_data *entry,
  			 struct diff_filespec *o,
  			 struct diff_filespec *a,
  			 struct diff_filespec *b)
  {
  	entry->processed = 0;
  	entry->stages[1].mode = o->mode;
  	entry->stages[2].mode = a->mode;
  	entry->stages[3].mode = b->mode;
  	hashcpy(entry->stages[1].sha, o->sha1);
  	hashcpy(entry->stages[2].sha, a->sha1);
  	hashcpy(entry->stages[3].sha, b->sha1);
  }
  
  static int remove_file(struct merge_options *o, int clean,
  		       const char *path, int no_wd)
  {
  	int update_cache = o->call_depth || clean;
  	int update_working_directory = !o->call_depth && !no_wd;
  
  	if (update_cache) {
  		if (remove_file_from_cache(path))
  			return -1;
  	}
  	if (update_working_directory) {
  		if (ignore_case) {
  			struct cache_entry *ce;
  			ce = cache_file_exists(path, strlen(path), ignore_case);
  			if (ce && ce_stage(ce) == 0)
  				return 0;
  		}
  		if (remove_path(path))
  			return -1;
  	}
  	return 0;
  }
  
  /* add a string to a strbuf, but converting "/" to "_" */
  static void add_flattened_path(struct strbuf *out, const char *s)
  {
  	size_t i = out->len;
  	strbuf_addstr(out, s);
  	for (; i < out->len; i++)
  		if (out->buf[i] == '/')
  			out->buf[i] = '_';
  }
  
  static char *unique_path(struct merge_options *o, const char *path, const char *branch)
  {
  	struct strbuf newpath = STRBUF_INIT;
  	int suffix = 0;
  	size_t base_len;
  
  	strbuf_addf(&newpath, "%s~", path);
  	add_flattened_path(&newpath, branch);
  
  	base_len = newpath.len;
  	while (string_list_has_string(&o->current_file_set, newpath.buf) ||
  	       string_list_has_string(&o->current_directory_set, newpath.buf) ||
  	       file_exists(newpath.buf)) {
  		strbuf_setlen(&newpath, base_len);
  		strbuf_addf(&newpath, "_%d", suffix++);
  	}
  
  	string_list_insert(&o->current_file_set, newpath.buf);
  	return strbuf_detach(&newpath, NULL);
  }
  
  static int dir_in_way(const char *path, int check_working_copy)
  {
  	int pos, pathlen = strlen(path);
  	char *dirpath = xmalloc(pathlen + 2);
  	struct stat st;
  
  	strcpy(dirpath, path);
  	dirpath[pathlen] = '/';
  	dirpath[pathlen+1] = '\0';
  
  	pos = cache_name_pos(dirpath, pathlen+1);
  
  	if (pos < 0)
  		pos = -1 - pos;
  	if (pos < active_nr &&
  	    !strncmp(dirpath, active_cache[pos]->name, pathlen+1)) {
  		free(dirpath);
  		return 1;
  	}
  
  	free(dirpath);
  	return check_working_copy && !lstat(path, &st) && S_ISDIR(st.st_mode);
  }
  
  static int was_tracked(const char *path)
  {
  	int pos = cache_name_pos(path, strlen(path));
  
  	if (pos < 0)
  		pos = -1 - pos;
  	while (pos < active_nr &&
  	       !strcmp(path, active_cache[pos]->name)) {
  		/*
  		 * If stage #0, it is definitely tracked.
  		 * If it has stage #2 then it was tracked
  		 * before this merge started.  All other
  		 * cases the path was not tracked.
  		 */
  		switch (ce_stage(active_cache[pos])) {
  		case 0:
  		case 2:
  			return 1;
  		}
  		pos++;
  	}
  	return 0;
  }
  
  static int would_lose_untracked(const char *path)
  {
  	return !was_tracked(path) && file_exists(path);
  }
  
  static int make_room_for_path(struct merge_options *o, const char *path)
  {
  	int status, i;
  	const char *msg = _("failed to create path '%s'%s");
  
  	/* Unlink any D/F conflict files that are in the way */
  	for (i = 0; i < o->df_conflict_file_set.nr; i++) {
  		const char *df_path = o->df_conflict_file_set.items[i].string;
  		size_t pathlen = strlen(path);
  		size_t df_pathlen = strlen(df_path);
  		if (df_pathlen < pathlen &&
  		    path[df_pathlen] == '/' &&
  		    strncmp(path, df_path, df_pathlen) == 0) {
  			output(o, 3,
  			       _("Removing %s to make room for subdirectory\n"),
  			       df_path);
  			unlink(df_path);
  			unsorted_string_list_delete_item(&o->df_conflict_file_set,
  							 i, 0);
  			break;
  		}
  	}
  
  	/* Make sure leading directories are created */
  	status = safe_create_leading_directories_const(path);
  	if (status) {
  		if (status == SCLD_EXISTS) {
  			/* something else exists */
  			error(msg, path, _(": perhaps a D/F conflict?"));
  			return -1;
  		}
  		die(msg, path, "");
  	}
  
  	/*
  	 * Do not unlink a file in the work tree if we are not
  	 * tracking it.
  	 */
  	if (would_lose_untracked(path))
  		return error(_("refusing to lose untracked file at '%s'"),
  			     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(struct merge_options *o,
  			      const unsigned char *sha,
  			      unsigned mode,
  			      const char *path,
  			      int update_cache,
  			      int update_wd)
  {
  	if (o->call_depth)
  		update_wd = 0;
  
  	if (update_wd) {
  		enum object_type type;
  		void *buf;
  		unsigned long size;
  
  		if (S_ISGITLINK(mode)) {
  			/*
  			 * We may later decide to recursively descend into
  			 * the submodule directory and update its index
  			 * and/or work tree, but we do not do that now.
  			 */
  			update_wd = 0;
  			goto update_index;
  		}
  
  		buf = read_sha1_file(sha, &type, &size);
  		if (!buf)
  			die(_("cannot read object %s '%s'"), sha1_to_hex(sha), path);
  		if (type != OBJ_BLOB)
  			die(_("blob expected for %s '%s'"), sha1_to_hex(sha), path);
  		if (S_ISREG(mode)) {
  			struct strbuf strbuf = STRBUF_INIT;
  			if (convert_to_working_tree(path, buf, size, &strbuf)) {
  				free(buf);
  				size = strbuf.len;
  				buf = strbuf_detach(&strbuf, NULL);
  			}
  		}
  
  		if (make_room_for_path(o, path) < 0) {
  			update_wd = 0;
  			free(buf);
  			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_errno(_("failed to open '%s'"), path);
  			write_in_full(fd, buf, size);
  			close(fd);
  		} else if (S_ISLNK(mode)) {
  			char *lnk = xmemdupz(buf, size);
  			safe_create_leading_directories_const(path);
  			unlink(path);
  			if (symlink(lnk, path))
  				die_errno(_("failed to symlink '%s'"), path);
  			free(lnk);
  		} else
  			die(_("do not know what to do with %06o %s '%s'"),
  			    mode, sha1_to_hex(sha), path);
  		free(buf);
  	}
   update_index:
  	if (update_cache)
  		add_cacheinfo(mode, sha, path, 0, update_wd, ADD_CACHE_OK_TO_ADD);
  }
  
  static void update_file(struct merge_options *o,
  			int clean,
  			const unsigned char *sha,
  			unsigned mode,
  			const char *path)
  {
  	update_file_flags(o, sha, mode, path, o->call_depth || clean, !o->call_depth);
  }
  
  /* Low level file merging, update and removal */
  
  struct merge_file_info {
  	unsigned char sha[20];
  	unsigned mode;
  	unsigned clean:1,
  		 merge:1;
  };
  
  static int merge_3way(struct merge_options *o,
  		      mmbuffer_t *result_buf,
  		      const struct diff_filespec *one,
  		      const struct diff_filespec *a,
  		      const struct diff_filespec *b,
  		      const char *branch1,
  		      const char *branch2)
  {
  	mmfile_t orig, src1, src2;
  	struct ll_merge_options ll_opts = {0};
  	char *base_name, *name1, *name2;
  	int merge_status;
  
  	ll_opts.renormalize = o->renormalize;
  	ll_opts.xdl_opts = o->xdl_opts;
  
  	if (o->call_depth) {
  		ll_opts.virtual_ancestor = 1;
  		ll_opts.variant = 0;
  	} else {
  		switch (o->recursive_variant) {
  		case MERGE_RECURSIVE_OURS:
  			ll_opts.variant = XDL_MERGE_FAVOR_OURS;
  			break;
  		case MERGE_RECURSIVE_THEIRS:
  			ll_opts.variant = XDL_MERGE_FAVOR_THEIRS;
  			break;
  		default:
  			ll_opts.variant = 0;
  			break;
  		}
  	}
  
  	if (strcmp(a->path, b->path) ||
  	    (o->ancestor != NULL && strcmp(a->path, one->path) != 0)) {
  		base_name = o->ancestor == NULL ? NULL :
  			mkpathdup("%s:%s", o->ancestor, one->path);
  		name1 = mkpathdup("%s:%s", branch1, a->path);
  		name2 = mkpathdup("%s:%s", branch2, b->path);
  	} else {
  		base_name = o->ancestor == NULL ? NULL :
  			mkpathdup("%s", o->ancestor);
  		name1 = mkpathdup("%s", branch1);
  		name2 = mkpathdup("%s", branch2);
  	}
  
  	read_mmblob(&orig, one->sha1);
  	read_mmblob(&src1, a->sha1);
  	read_mmblob(&src2, b->sha1);
  
  	merge_status = ll_merge(result_buf, a->path, &orig, base_name,
  				&src1, name1, &src2, name2, &ll_opts);
  
  	free(base_name);
  	free(name1);
  	free(name2);
  	free(orig.ptr);
  	free(src1.ptr);
  	free(src2.ptr);
  	return merge_status;
  }
  
  static struct merge_file_info merge_file_1(struct merge_options *o,
  					   const struct diff_filespec *one,
  					   const struct diff_filespec *a,
  					   const 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, one->sha1) && !sha_eq(b->sha1, one->sha1))
  			result.merge = 1;
  
  		/*
  		 * Merge modes
  		 */
  		if (a->mode == b->mode || a->mode == one->mode)
  			result.mode = b->mode;
  		else {
  			result.mode = a->mode;
  			if (b->mode != one->mode) {
  				result.clean = 0;
  				result.merge = 1;
  			}
  		}
  
  		if (sha_eq(a->sha1, b->sha1) || sha_eq(a->sha1, one->sha1))
  			hashcpy(result.sha, b->sha1);
  		else if (sha_eq(b->sha1, one->sha1))
  			hashcpy(result.sha, a->sha1);
  		else if (S_ISREG(a->mode)) {
  			mmbuffer_t result_buf;
  			int merge_status;
  
  			merge_status = merge_3way(o, &result_buf, one, 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 = merge_submodule(result.sha,
  						       one->path, one->sha1,
  						       a->sha1, b->sha1,
  						       !o->call_depth);
  		} 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 struct merge_file_info
  merge_file_special_markers(struct merge_options *o,
  			   const struct diff_filespec *one,
  			   const struct diff_filespec *a,
  			   const struct diff_filespec *b,
  			   const char *branch1,
  			   const char *filename1,
  			   const char *branch2,
  			   const char *filename2)
  {
  	char *side1 = NULL;
  	char *side2 = NULL;
  	struct merge_file_info mfi;
  
  	if (filename1)
  		side1 = xstrfmt("%s:%s", branch1, filename1);
  	if (filename2)
  		side2 = xstrfmt("%s:%s", branch2, filename2);
  
  	mfi = merge_file_1(o, one, a, b,
  			   side1 ? side1 : branch1, side2 ? side2 : branch2);
  	free(side1);
  	free(side2);
  	return mfi;
  }
  
  static struct merge_file_info merge_file_one(struct merge_options *o,
  					 const char *path,
  					 const unsigned char *o_sha, int o_mode,
  					 const unsigned char *a_sha, int a_mode,
  					 const unsigned char *b_sha, int b_mode,
  					 const char *branch1,
  					 const char *branch2)
  {
  	struct diff_filespec one, a, b;
  
  	one.path = a.path = b.path = (char *)path;
  	hashcpy(one.sha1, o_sha);
  	one.mode = o_mode;
  	hashcpy(a.sha1, a_sha);
  	a.mode = a_mode;
  	hashcpy(b.sha1, b_sha);
  	b.mode = b_mode;
  	return merge_file_1(o, &one, &a, &b, branch1, branch2);
  }
  
  static void handle_change_delete(struct merge_options *o,
  				 const char *path,
  				 const unsigned char *o_sha, int o_mode,
  				 const unsigned char *a_sha, int a_mode,
  				 const unsigned char *b_sha, int b_mode,
  				 const char *change, const char *change_past)
  {
  	char *renamed = NULL;
  	if (dir_in_way(path, !o->call_depth)) {
  		renamed = unique_path(o, path, a_sha ? o->branch1 : o->branch2);
  	}
  
  	if (o->call_depth) {
  		/*
  		 * We cannot arbitrarily accept either a_sha or b_sha as
  		 * correct; since there is no true "middle point" between
  		 * them, simply reuse the base version for virtual merge base.
  		 */
  		remove_file_from_cache(path);
  		update_file(o, 0, o_sha, o_mode, renamed ? renamed : path);
  	} else if (!a_sha) {
  		if (!renamed) {
  			output(o, 1, _("CONFLICT (%s/delete): %s deleted in %s "
  			       "and %s in %s. Version %s of %s left in tree."),
  			       change, path, o->branch1, change_past,
  			       o->branch2, o->branch2, path);
  			update_file(o, 0, b_sha, b_mode, path);
  		} else {
  			output(o, 1, _("CONFLICT (%s/delete): %s deleted in %s "
  			       "and %s in %s. Version %s of %s left in tree at %s."),
  			       change, path, o->branch1, change_past,
  			       o->branch2, o->branch2, path, renamed);
  			update_file(o, 0, b_sha, b_mode, renamed);
  		}
  	} else {
  		if (!renamed) {
  			output(o, 1, _("CONFLICT (%s/delete): %s deleted in %s "
  			       "and %s in %s. Version %s of %s left in tree."),
  			       change, path, o->branch2, change_past,
  			       o->branch1, o->branch1, path);
  		} else {
  			output(o, 1, _("CONFLICT (%s/delete): %s deleted in %s "
  			       "and %s in %s. Version %s of %s left in tree at %s."),
  			       change, path, o->branch2, change_past,
  			       o->branch1, o->branch1, path, renamed);
  			update_file(o, 0, a_sha, a_mode, renamed);
  		}
  		/*
  		 * No need to call update_file() on path when !renamed, since
  		 * that would needlessly touch path.  We could call
  		 * update_file_flags() with update_cache=0 and update_wd=0,
  		 * but that's a no-op.
  		 */
  	}
  	free(renamed);
  }
  
  static void conflict_rename_delete(struct merge_options *o,
  				   struct diff_filepair *pair,
  				   const char *rename_branch,
  				   const char *other_branch)
  {
  	const struct diff_filespec *orig = pair->one;
  	const struct diff_filespec *dest = pair->two;
  	const unsigned char *a_sha = NULL;
  	const unsigned char *b_sha = NULL;
  	int a_mode = 0;
  	int b_mode = 0;
  
  	if (rename_branch == o->branch1) {
  		a_sha = dest->sha1;
  		a_mode = dest->mode;
  	} else {
  		b_sha = dest->sha1;
  		b_mode = dest->mode;
  	}
  
  	handle_change_delete(o,
  			     o->call_depth ? orig->path : dest->path,
  			     orig->sha1, orig->mode,
  			     a_sha, a_mode,
  			     b_sha, b_mode,
  			     _("rename"), _("renamed"));
  
  	if (o->call_depth) {
  		remove_file_from_cache(dest->path);
  	} else {
  		update_stages(dest->path, NULL,
  			      rename_branch == o->branch1 ? dest : NULL,
  			      rename_branch == o->branch1 ? NULL : dest);
  	}
  
  }
  
  static struct diff_filespec *filespec_from_entry(struct diff_filespec *target,
  						 struct stage_data *entry,
  						 int stage)
  {
  	unsigned char *sha = entry->stages[stage].sha;
  	unsigned mode = entry->stages[stage].mode;
  	if (mode == 0 || is_null_sha1(sha))
  		return NULL;
  	hashcpy(target->sha1, sha);
  	target->mode = mode;
  	return target;
  }
  
  static void handle_file(struct merge_options *o,
  			struct diff_filespec *rename,
  			int stage,
  			struct rename_conflict_info *ci)
  {
  	char *dst_name = rename->path;
  	struct stage_data *dst_entry;
  	const char *cur_branch, *other_branch;
  	struct diff_filespec other;
  	struct diff_filespec *add;
  
  	if (stage == 2) {
  		dst_entry = ci->dst_entry1;
  		cur_branch = ci->branch1;
  		other_branch = ci->branch2;
  	} else {
  		dst_entry = ci->dst_entry2;
  		cur_branch = ci->branch2;
  		other_branch = ci->branch1;
  	}
  
  	add = filespec_from_entry(&other, dst_entry, stage ^ 1);
  	if (add) {
  		char *add_name = unique_path(o, rename->path, other_branch);
  		update_file(o, 0, add->sha1, add->mode, add_name);
  
  		remove_file(o, 0, rename->path, 0);
  		dst_name = unique_path(o, rename->path, cur_branch);
  	} else {
  		if (dir_in_way(rename->path, !o->call_depth)) {
  			dst_name = unique_path(o, rename->path, cur_branch);
  			output(o, 1, _("%s is a directory in %s adding as %s instead"),
  			       rename->path, other_branch, dst_name);
  		}
  	}
  	update_file(o, 0, rename->sha1, rename->mode, dst_name);
  	if (stage == 2)
  		update_stages(rename->path, NULL, rename, add);
  	else
  		update_stages(rename->path, NULL, add, rename);
  
  	if (dst_name != rename->path)
  		free(dst_name);
  }
  
  static void conflict_rename_rename_1to2(struct merge_options *o,
  					struct rename_conflict_info *ci)
  {
  	/* One file was renamed in both branches, but to different names. */
  	struct diff_filespec *one = ci->pair1->one;
  	struct diff_filespec *a = ci->pair1->two;
  	struct diff_filespec *b = ci->pair2->two;
  
  	output(o, 1, _("CONFLICT (rename/rename): "
  	       "Rename \"%s\"->\"%s\" in branch \"%s\" "
  	       "rename \"%s\"->\"%s\" in \"%s\"%s"),
  	       one->path, a->path, ci->branch1,
  	       one->path, b->path, ci->branch2,
  	       o->call_depth ? _(" (left unresolved)") : "");
  	if (o->call_depth) {
  		struct merge_file_info mfi;
  		struct diff_filespec other;
  		struct diff_filespec *add;
  		mfi = merge_file_one(o, one->path,
  				 one->sha1, one->mode,
  				 a->sha1, a->mode,
  				 b->sha1, b->mode,
  				 ci->branch1, ci->branch2);
  		/*
  		 * FIXME: For rename/add-source conflicts (if we could detect
  		 * such), this is wrong.  We should instead find a unique
  		 * pathname and then either rename the add-source file to that
  		 * unique path, or use that unique path instead of src here.
  		 */
  		update_file(o, 0, mfi.sha, mfi.mode, one->path);
  
  		/*
  		 * Above, we put the merged content at the merge-base's
  		 * path.  Now we usually need to delete both a->path and
  		 * b->path.  However, the rename on each side of the merge
  		 * could also be involved in a rename/add conflict.  In
  		 * such cases, we should keep the added file around,
  		 * resolving the conflict at that path in its favor.
  		 */
  		add = filespec_from_entry(&other, ci->dst_entry1, 2 ^ 1);
  		if (add)
  			update_file(o, 0, add->sha1, add->mode, a->path);
  		else
  			remove_file_from_cache(a->path);
  		add = filespec_from_entry(&other, ci->dst_entry2, 3 ^ 1);
  		if (add)
  			update_file(o, 0, add->sha1, add->mode, b->path);
  		else
  			remove_file_from_cache(b->path);
  	} else {
  		handle_file(o, a, 2, ci);
  		handle_file(o, b, 3, ci);
  	}
  }
  
  static void conflict_rename_rename_2to1(struct merge_options *o,
  					struct rename_conflict_info *ci)
  {
  	/* Two files, a & b, were renamed to the same thing, c. */
  	struct diff_filespec *a = ci->pair1->one;
  	struct diff_filespec *b = ci->pair2->one;
  	struct diff_filespec *c1 = ci->pair1->two;
  	struct diff_filespec *c2 = ci->pair2->two;
  	char *path = c1->path; /* == c2->path */
  	struct merge_file_info mfi_c1;
  	struct merge_file_info mfi_c2;
  
  	output(o, 1, _("CONFLICT (rename/rename): "
  	       "Rename %s->%s in %s. "
  	       "Rename %s->%s in %s"),
  	       a->path, c1->path, ci->branch1,
  	       b->path, c2->path, ci->branch2);
  
  	remove_file(o, 1, a->path, would_lose_untracked(a->path));
  	remove_file(o, 1, b->path, would_lose_untracked(b->path));
  
  	mfi_c1 = merge_file_special_markers(o, a, c1, &ci->ren1_other,
  					    o->branch1, c1->path,
  					    o->branch2, ci->ren1_other.path);
  	mfi_c2 = merge_file_special_markers(o, b, &ci->ren2_other, c2,
  					    o->branch1, ci->ren2_other.path,
  					    o->branch2, c2->path);
  
  	if (o->call_depth) {
  		/*
  		 * If mfi_c1.clean && mfi_c2.clean, then it might make
  		 * sense to do a two-way merge of those results.  But, I
  		 * think in all cases, it makes sense to have the virtual
  		 * merge base just undo the renames; they can be detected
  		 * again later for the non-recursive merge.
  		 */
  		remove_file(o, 0, path, 0);
  		update_file(o, 0, mfi_c1.sha, mfi_c1.mode, a->path);
  		update_file(o, 0, mfi_c2.sha, mfi_c2.mode, b->path);
  	} else {
  		char *new_path1 = unique_path(o, path, ci->branch1);
  		char *new_path2 = unique_path(o, path, ci->branch2);
  		output(o, 1, _("Renaming %s to %s and %s to %s instead"),
  		       a->path, new_path1, b->path, new_path2);
  		remove_file(o, 0, path, 0);
  		update_file(o, 0, mfi_c1.sha, mfi_c1.mode, new_path1);
  		update_file(o, 0, mfi_c2.sha, mfi_c2.mode, new_path2);
  		free(new_path2);
  		free(new_path1);
  	}
  }
  
  static int process_renames(struct merge_options *o,
  			   struct string_list *a_renames,
  			   struct string_list *b_renames)
  {
  	int clean_merge = 1, i, j;
  	struct string_list a_by_dst = STRING_LIST_INIT_NODUP;
  	struct string_list b_by_dst = STRING_LIST_INIT_NODUP;
  	const struct rename *sre;
  
  	for (i = 0; i < a_renames->nr; i++) {
  		sre = a_renames->items[i].util;
  		string_list_insert(&a_by_dst, sre->pair->two->path)->util
  			= (void *)sre;
  	}
  	for (i = 0; i < b_renames->nr; i++) {
  		sre = b_renames->items[i].util;
  		string_list_insert(&b_by_dst, sre->pair->two->path)->util
  			= (void *)sre;
  	}
  
  	for (i = 0, j = 0; i < a_renames->nr || j < b_renames->nr;) {
  		struct string_list *renames1, *renames2Dst;
  		struct rename *ren1 = NULL, *ren2 = NULL;
  		const char *branch1, *branch2;
  		const char *ren1_src, *ren1_dst;
  		struct string_list_item *lookup;
  
  		if (i >= a_renames->nr) {
  			ren2 = b_renames->items[j++].util;
  		} else if (j >= b_renames->nr) {
  			ren1 = a_renames->items[i++].util;
  		} else {
  			int compare = strcmp(a_renames->items[i].string,
  					     b_renames->items[j].string);
  			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;
  			renames2Dst = &b_by_dst;
  			branch1 = o->branch1;
  			branch2 = o->branch2;
  		} else {
  			struct rename *tmp;
  			renames1 = b_renames;
  			renames2Dst = &a_by_dst;
  			branch1 = o->branch2;
  			branch2 = o->branch1;
  			tmp = ren2;
  			ren2 = ren1;
  			ren1 = tmp;
  		}
  
  		if (ren1->processed)
  			continue;
  		ren1->processed = 1;
  		ren1->dst_entry->processed = 1;
  		/* BUG: We should only mark src_entry as processed if we
  		 * are not dealing with a rename + add-source case.
  		 */
  		ren1->src_entry->processed = 1;
  
  		ren1_src = ren1->pair->one->path;
  		ren1_dst = ren1->pair->two->path;
  
  		if (ren2) {
  			/* One file renamed on both sides */
  			const char *ren2_src = ren2->pair->one->path;
  			const char *ren2_dst = ren2->pair->two->path;
  			enum rename_type rename_type;
  			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) {
  				rename_type = RENAME_ONE_FILE_TO_TWO;
  				clean_merge = 0;
  			} else {
  				rename_type = RENAME_ONE_FILE_TO_ONE;
  				/* BUG: We should only remove ren1_src in
  				 * the base stage (think of rename +
  				 * add-source cases).
  				 */
  				remove_file(o, 1, ren1_src, 1);
  				update_entry(ren1->dst_entry,
  					     ren1->pair->one,
  					     ren1->pair->two,
  					     ren2->pair->two);
  			}
  			setup_rename_conflict_info(rename_type,
  						   ren1->pair,
  						   ren2->pair,
  						   branch1,
  						   branch2,
  						   ren1->dst_entry,
  						   ren2->dst_entry,
  						   o,
  						   NULL,
  						   NULL);
  		} else if ((lookup = string_list_lookup(renames2Dst, ren1_dst))) {
  			/* Two different files renamed to the same thing */
  			char *ren2_dst;
  			ren2 = lookup->util;
  			ren2_dst = ren2->pair->two->path;
  			if (strcmp(ren1_dst, ren2_dst) != 0)
  				die("ren1_dst != ren2_dst");
  
  			clean_merge = 0;
  			ren2->processed = 1;
  			/*
  			 * BUG: We should only mark src_entry as processed
  			 * if we are not dealing with a rename + add-source
  			 * case.
  			 */
  			ren2->src_entry->processed = 1;
  
  			setup_rename_conflict_info(RENAME_TWO_FILES_TO_ONE,
  						   ren1->pair,
  						   ren2->pair,
  						   branch1,
  						   branch2,
  						   ren1->dst_entry,
  						   ren2->dst_entry,
  						   o,
  						   ren1->src_entry,
  						   ren2->src_entry);
  
  		} else {
  			/* Renamed in 1, maybe changed in 2 */
  			/* we only use sha1 and mode of these */
  			struct diff_filespec src_other, dst_other;
  			int try_merge;
  
  			/*
  			 * unpack_trees loads entries from common-commit
  			 * into stage 1, from head-commit into stage 2, and
  			 * from merge-commit into stage 3.  We keep track
  			 * of which side corresponds to the rename.
  			 */
  			int renamed_stage = a_renames == renames1 ? 2 : 3;
  			int other_stage =   a_renames == renames1 ? 3 : 2;
  
  			/* BUG: We should only remove ren1_src in the base
  			 * stage and in other_stage (think of rename +
  			 * add-source case).
  			 */
  			remove_file(o, 1, ren1_src,
  				    renamed_stage == 2 || !was_tracked(ren1_src));
  
  			hashcpy(src_other.sha1, ren1->src_entry->stages[other_stage].sha);
  			src_other.mode = ren1->src_entry->stages[other_stage].mode;
  			hashcpy(dst_other.sha1, ren1->dst_entry->stages[other_stage].sha);
  			dst_other.mode = ren1->dst_entry->stages[other_stage].mode;
  			try_merge = 0;
  
  			if (sha_eq(src_other.sha1, null_sha1)) {
  				setup_rename_conflict_info(RENAME_DELETE,
  							   ren1->pair,
  							   NULL,
  							   branch1,
  							   branch2,
  							   ren1->dst_entry,
  							   NULL,
  							   o,
  							   NULL,
  							   NULL);
  			} else if ((dst_other.mode == ren1->pair->two->mode) &&
  				   sha_eq(dst_other.sha1, ren1->pair->two->sha1)) {
  				/*
  				 * Added file on the other side identical to
  				 * the file being renamed: clean merge.
  				 * Also, there is no need to overwrite the
  				 * file already in the working copy, so call
  				 * update_file_flags() instead of
  				 * update_file().
  				 */
  				update_file_flags(o,
  						  ren1->pair->two->sha1,
  						  ren1->pair->two->mode,
  						  ren1_dst,
  						  1, /* update_cache */
  						  0  /* update_wd    */);
  			} else if (!sha_eq(dst_other.sha1, null_sha1)) {
  				clean_merge = 0;
  				try_merge = 1;
  				output(o, 1, _("CONFLICT (rename/add): Rename %s->%s in %s. "
  				       "%s added in %s"),
  				       ren1_src, ren1_dst, branch1,
  				       ren1_dst, branch2);
  				if (o->call_depth) {
  					struct merge_file_info mfi;
  					mfi = merge_file_one(o, ren1_dst, null_sha1, 0,
  							 ren1->pair->two->sha1, ren1->pair->two->mode,
  							 dst_other.sha1, dst_other.mode,
  							 branch1, branch2);
  					output(o, 1, _("Adding merged %s"), ren1_dst);
  					update_file(o, 0, mfi.sha, mfi.mode, ren1_dst);
  					try_merge = 0;
  				} else {
  					char *new_path = unique_path(o, ren1_dst, branch2);
  					output(o, 1, _("Adding as %s instead"), new_path);
  					update_file(o, 0, dst_other.sha1, dst_other.mode, new_path);
  					free(new_path);
  				}
  			} else
  				try_merge = 1;
  
  			if (try_merge) {
  				struct diff_filespec *one, *a, *b;
  				src_other.path = (char *)ren1_src;
  
  				one = ren1->pair->one;
  				if (a_renames == renames1) {
  					a = ren1->pair->two;
  					b = &src_other;
  				} else {
  					b = ren1->pair->two;
  					a = &src_other;
  				}
  				update_entry(ren1->dst_entry, one, a, b);
  				setup_rename_conflict_info(RENAME_NORMAL,
  							   ren1->pair,
  							   NULL,
  							   branch1,
  							   NULL,
  							   ren1->dst_entry,
  							   NULL,
  							   o,
  							   NULL,
  							   NULL);
  			}
  		}
  	}
  	string_list_clear(&a_by_dst, 0);
  	string_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;
  }
  
  static int read_sha1_strbuf(const unsigned char *sha1, struct strbuf *dst)
  {
  	void *buf;
  	enum object_type type;
  	unsigned long size;
  	buf = read_sha1_file(sha1, &type, &size);
  	if (!buf)
  		return error(_("cannot read object %s"), sha1_to_hex(sha1));
  	if (type != OBJ_BLOB) {
  		free(buf);
  		return error(_("object %s is not a blob"), sha1_to_hex(sha1));
  	}
  	strbuf_attach(dst, buf, size, size + 1);
  	return 0;
  }
  
  static int blob_unchanged(const unsigned char *o_sha,
  			  const unsigned char *a_sha,
  			  int renormalize, const char *path)
  {
  	struct strbuf o = STRBUF_INIT;
  	struct strbuf a = STRBUF_INIT;
  	int ret = 0; /* assume changed for safety */
  
  	if (sha_eq(o_sha, a_sha))
  		return 1;
  	if (!renormalize)
  		return 0;
  
  	assert(o_sha && a_sha);
  	if (read_sha1_strbuf(o_sha, &o) || read_sha1_strbuf(a_sha, &a))
  		goto error_return;
  	/*
  	 * Note: binary | is used so that both renormalizations are
  	 * performed.  Comparison can be skipped if both files are
  	 * unchanged since their sha1s have already been compared.
  	 */
  	if (renormalize_buffer(path, o.buf, o.len, &o) |
  	    renormalize_buffer(path, a.buf, a.len, &a))
  		ret = (o.len == a.len && !memcmp(o.buf, a.buf, o.len));
  
  error_return:
  	strbuf_release(&o);
  	strbuf_release(&a);
  	return ret;
  }
  
  static void handle_modify_delete(struct merge_options *o,
  				 const char *path,
  				 unsigned char *o_sha, int o_mode,
  				 unsigned char *a_sha, int a_mode,
  				 unsigned char *b_sha, int b_mode)
  {
  	handle_change_delete(o,
  			     path,
  			     o_sha, o_mode,
  			     a_sha, a_mode,
  			     b_sha, b_mode,
  			     _("modify"), _("modified"));
  }
  
  static int merge_content(struct merge_options *o,
  			 const char *path,
  			 unsigned char *o_sha, int o_mode,
  			 unsigned char *a_sha, int a_mode,
  			 unsigned char *b_sha, int b_mode,
  			 struct rename_conflict_info *rename_conflict_info)
  {
  	const char *reason = _("content");
  	const char *path1 = NULL, *path2 = NULL;
  	struct merge_file_info mfi;
  	struct diff_filespec one, a, b;
  	unsigned df_conflict_remains = 0;
  
  	if (!o_sha) {
  		reason = _("add/add");
  		o_sha = (unsigned char *)null_sha1;
  	}
  	one.path = a.path = b.path = (char *)path;
  	hashcpy(one.sha1, o_sha);
  	one.mode = o_mode;
  	hashcpy(a.sha1, a_sha);
  	a.mode = a_mode;
  	hashcpy(b.sha1, b_sha);
  	b.mode = b_mode;
  
  	if (rename_conflict_info) {
  		struct diff_filepair *pair1 = rename_conflict_info->pair1;
  
  		path1 = (o->branch1 == rename_conflict_info->branch1) ?
  			pair1->two->path : pair1->one->path;
  		/* If rename_conflict_info->pair2 != NULL, we are in
  		 * RENAME_ONE_FILE_TO_ONE case.  Otherwise, we have a
  		 * normal rename.
  		 */
  		path2 = (rename_conflict_info->pair2 ||
  			 o->branch2 == rename_conflict_info->branch1) ?
  			pair1->two->path : pair1->one->path;
  
  		if (dir_in_way(path, !o->call_depth))
  			df_conflict_remains = 1;
  	}
  	mfi = merge_file_special_markers(o, &one, &a, &b,
  					 o->branch1, path1,
  					 o->branch2, path2);
  
  	if (mfi.clean && !df_conflict_remains &&
  	    sha_eq(mfi.sha, a_sha) && mfi.mode == a_mode) {
  		int path_renamed_outside_HEAD;
  		output(o, 3, _("Skipped %s (merged same as existing)"), path);
  		/*
  		 * The content merge resulted in the same file contents we
  		 * already had.  We can return early if those file contents
  		 * are recorded at the correct path (which may not be true
  		 * if the merge involves a rename).
  		 */
  		path_renamed_outside_HEAD = !path2 || !strcmp(path, path2);
  		if (!path_renamed_outside_HEAD) {
  			add_cacheinfo(mfi.mode, mfi.sha, path,
  				      0, (!o->call_depth), 0);
  			return mfi.clean;
  		}
  	} else
  		output(o, 2, _("Auto-merging %s"), path);
  
  	if (!mfi.clean) {
  		if (S_ISGITLINK(mfi.mode))
  			reason = _("submodule");
  		output(o, 1, _("CONFLICT (%s): Merge conflict in %s"),
  				reason, path);
  		if (rename_conflict_info && !df_conflict_remains)
  			update_stages(path, &one, &a, &b);
  	}
  
  	if (df_conflict_remains) {
  		char *new_path;
  		if (o->call_depth) {
  			remove_file_from_cache(path);
  		} else {
  			if (!mfi.clean)
  				update_stages(path, &one, &a, &b);
  			else {
  				int file_from_stage2 = was_tracked(path);
  				struct diff_filespec merged;
  				hashcpy(merged.sha1, mfi.sha);
  				merged.mode = mfi.mode;
  
  				update_stages(path, NULL,
  					      file_from_stage2 ? &merged : NULL,
  					      file_from_stage2 ? NULL : &merged);
  			}
  
  		}
  		new_path = unique_path(o, path, rename_conflict_info->branch1);
  		output(o, 1, _("Adding as %s instead"), new_path);
  		update_file(o, 0, mfi.sha, mfi.mode, new_path);
  		free(new_path);
  		mfi.clean = 0;
  	} else {
  		update_file(o, mfi.clean, mfi.sha, mfi.mode, path);
  	}
  	return mfi.clean;
  
  }
  
  /* Per entry merge function */
  static int process_entry(struct merge_options *o,
  			 const char *path, struct stage_data *entry)
  {
  	int clean_merge = 1;
  	int normalize = o->renormalize;
  	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);
  
  	entry->processed = 1;
  	if (entry->rename_conflict_info) {
  		struct rename_conflict_info *conflict_info = entry->rename_conflict_info;
  		switch (conflict_info->rename_type) {
  		case RENAME_NORMAL:
  		case RENAME_ONE_FILE_TO_ONE:
  			clean_merge = merge_content(o, path,
  						    o_sha, o_mode, a_sha, a_mode, b_sha, b_mode,
  						    conflict_info);
  			break;
  		case RENAME_DELETE:
  			clean_merge = 0;
  			conflict_rename_delete(o, conflict_info->pair1,
  					       conflict_info->branch1,
  					       conflict_info->branch2);
  			break;
  		case RENAME_ONE_FILE_TO_TWO:
  			clean_merge = 0;
  			conflict_rename_rename_1to2(o, conflict_info);
  			break;
  		case RENAME_TWO_FILES_TO_ONE:
  			clean_merge = 0;
  			conflict_rename_rename_2to1(o, conflict_info);
  			break;
  		default:
  			entry->processed = 0;
  			break;
  		}
  	} else if (o_sha && (!a_sha || !b_sha)) {
  		/* Case A: Deleted in one */
  		if ((!a_sha && !b_sha) ||
  		    (!b_sha && blob_unchanged(o_sha, a_sha, normalize, path)) ||
  		    (!a_sha && blob_unchanged(o_sha, b_sha, normalize, path))) {
  			/* Deleted in both or deleted in one and
  			 * unchanged in the other */
  			if (a_sha)
  				output(o, 2, _("Removing %s"), path);
  			/* do not touch working file if it did not exist */
  			remove_file(o, 1, path, !a_sha);
  		} else {
  			/* Modify/delete; deleted side may have put a directory in the way */
  			clean_merge = 0;
  			handle_modify_delete(o, path, o_sha, o_mode,
  					     a_sha, a_mode, b_sha, b_mode);
  		}
  	} else if ((!o_sha && a_sha && !b_sha) ||
  		   (!o_sha && !a_sha && b_sha)) {
  		/* Case B: Added in one. */
  		/* [nothing|directory] -> ([nothing|directory], file) */
  
  		const char *add_branch;
  		const char *other_branch;
  		unsigned mode;
  		const unsigned char *sha;
  		const char *conf;
  
  		if (a_sha) {
  			add_branch = o->branch1;
  			other_branch = o->branch2;
  			mode = a_mode;
  			sha = a_sha;
  			conf = _("file/directory");
  		} else {
  			add_branch = o->branch2;
  			other_branch = o->branch1;
  			mode = b_mode;
  			sha = b_sha;
  			conf = _("directory/file");
  		}
  		if (dir_in_way(path, !o->call_depth)) {
  			char *new_path = unique_path(o, path, add_branch);
  			clean_merge = 0;
  			output(o, 1, _("CONFLICT (%s): There is a directory with name %s in %s. "
  			       "Adding %s as %s"),
  			       conf, path, other_branch, path, new_path);
  			if (o->call_depth)
  				remove_file_from_cache(path);
  			update_file(o, 0, sha, mode, new_path);
  			if (o->call_depth)
  				remove_file_from_cache(path);
  			free(new_path);
  		} else {
  			output(o, 2, _("Adding %s"), path);
  			/* do not overwrite file if already present */
  			update_file_flags(o, sha, mode, path, 1, !a_sha);
  		}
  	} else if (a_sha && b_sha) {
  		/* Case C: Added in both (check for same permissions) and */
  		/* case D: Modified in both, but differently. */
  		clean_merge = merge_content(o, path,
  					    o_sha, o_mode, a_sha, a_mode, b_sha, b_mode,
  					    NULL);
  	} 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(o, 1, path, !a_mode);
  	} else
  		die(_("Fatal merge failure, shouldn't happen."));
  
  	return clean_merge;
  }
  
  int merge_trees(struct merge_options *o,
  		struct tree *head,
  		struct tree *merge,
  		struct tree *common,
  		struct tree **result)
  {
  	int code, clean;
  
  	if (o->subtree_shift) {
  		merge = shift_tree_object(head, merge, o->subtree_shift);
  		common = shift_tree_object(head, common, o->subtree_shift);
  	}
  
  	if (sha_eq(common->object.sha1, merge->object.sha1)) {
  		output(o, 0, _("Already up-to-date!"));
  		*result = head;
  		return 1;
  	}
  
  	code = git_merge_trees(o->call_depth, common, head, merge);
  
  	if (code != 0) {
  		if (show(o, 4) || o->call_depth)
  			die(_("merging of trees %s and %s failed"),
  			    sha1_to_hex(head->object.sha1),
  			    sha1_to_hex(merge->object.sha1));
  		else
  			exit(128);
  	}
  
  	if (unmerged_cache()) {
  		struct string_list *entries, *re_head, *re_merge;
  		int i;
  		string_list_clear(&o->current_file_set, 1);
  		string_list_clear(&o->current_directory_set, 1);
  		get_files_dirs(o, head);
  		get_files_dirs(o, merge);
  
  		entries = get_unmerged();
  		record_df_conflict_files(o, entries);
  		re_head  = get_renames(o, head, common, head, merge, entries);
  		re_merge = get_renames(o, merge, common, head, merge, entries);
  		clean = process_renames(o, re_head, re_merge);
  		for (i = entries->nr-1; 0 <= i; i--) {
  			const char *path = entries->items[i].string;
  			struct stage_data *e = entries->items[i].util;
  			if (!e->processed
  				&& !process_entry(o, path, e))
  				clean = 0;
  		}
  		for (i = 0; i < entries->nr; i++) {
  			struct stage_data *e = entries->items[i].util;
  			if (!e->processed)
  				die(_("Unprocessed path??? %s"),
  				    entries->items[i].string);
  		}
  
  		string_list_clear(re_merge, 0);
  		string_list_clear(re_head, 0);
  		string_list_clear(entries, 1);
  
  		free(re_merge);
  		free(re_head);
  		free(entries);
  	}
  	else
  		clean = 1;
  
  	if (o->call_depth)
  		*result = write_tree_from_memory(o);
  
  	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 merge_options *o,
  		    struct commit *h1,
  		    struct commit *h2,
  		    struct commit_list *ca,
  		    struct commit **result)
  {
  	struct commit_list *iter;
  	struct commit *merged_common_ancestors;
  	struct tree *mrtree = mrtree;
  	int clean;
  
  	if (show(o, 4)) {
  		output(o, 4, _("Merging:"));
  		output_commit_title(o, h1);
  		output_commit_title(o, h2);
  	}
  
  	if (!ca) {
  		ca = get_merge_bases(h1, h2);
  		ca = reverse_commit_list(ca);
  	}
  
  	if (show(o, 5)) {
  		unsigned cnt = commit_list_count(ca);
  
  		output(o, 5, Q_("found %u common ancestor:",
  				"found %u common ancestors:", cnt), cnt);
  		for (iter = ca; iter; iter = iter->next)
  			output_commit_title(o, iter->item);
  	}
  
  	merged_common_ancestors = pop_commit(&ca);
  	if (merged_common_ancestors == NULL) {
  		/* if there is no common ancestor, use an empty tree */
  		struct tree *tree;
  
  		tree = lookup_tree(EMPTY_TREE_SHA1_BIN);
  		merged_common_ancestors = make_virtual_commit(tree, "ancestor");
  	}
  
  	for (iter = ca; iter; iter = iter->next) {
  		const char *saved_b1, *saved_b2;
  		o->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();
  		saved_b1 = o->branch1;
  		saved_b2 = o->branch2;
  		o->branch1 = "Temporary merge branch 1";
  		o->branch2 = "Temporary merge branch 2";
  		merge_recursive(o, merged_common_ancestors, iter->item,
  				NULL, &merged_common_ancestors);
  		o->branch1 = saved_b1;
  		o->branch2 = saved_b2;
  		o->call_depth--;
  
  		if (!merged_common_ancestors)
  			die(_("merge returned no commit"));
  	}
  
  	discard_cache();
  	if (!o->call_depth)
  		read_cache();
  
  	o->ancestor = "merged common ancestors";
  	clean = merge_trees(o, h1->tree, h2->tree, merged_common_ancestors->tree,
  			    &mrtree);
  
  	if (o->call_depth) {
  		*result = make_virtual_commit(mrtree, "merged tree");
  		commit_list_insert(h1, &(*result)->parents);
  		commit_list_insert(h2, &(*result)->parents->next);
  	}
  	flush_output(o);
  	if (show(o, 2))
  		diff_warn_rename_limit("merge.renamelimit",
  				       o->needed_rename_limit, 0);
  	return clean;
  }
  
  static struct commit *get_ref(const unsigned char *sha1, const char *name)
  {
  	struct object *object;
  
  	object = deref_tag(parse_object(sha1), name, strlen(name));
  	if (!object)
  		return NULL;
  	if (object->type == OBJ_TREE)
  		return make_virtual_commit((struct tree*)object, name);
  	if (object->type != OBJ_COMMIT)
  		return NULL;
  	if (parse_commit((struct commit *)object))
  		return NULL;
  	return (struct commit *)object;
  }
  
  int merge_recursive_generic(struct merge_options *o,
  			    const unsigned char *head,
  			    const unsigned char *merge,
  			    int num_base_list,
  			    const unsigned char **base_list,
  			    struct commit **result)
  {
  	int clean;
  	struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
  	struct commit *head_commit = get_ref(head, o->branch1);
  	struct commit *next_commit = get_ref(merge, o->branch2);
  	struct commit_list *ca = NULL;
  
  	if (base_list) {
  		int i;
  		for (i = 0; i < num_base_list; ++i) {
  			struct commit *base;
  			if (!(base = get_ref(base_list[i], sha1_to_hex(base_list[i]))))
  				return error(_("Could not parse object '%s'"),
  					sha1_to_hex(base_list[i]));
  			commit_list_insert(base, &ca);
  		}
  	}
  
  	hold_locked_index(lock, 1);
  	clean = merge_recursive(o, head_commit, next_commit, ca,
  			result);
  	if (active_cache_changed &&
  	    write_locked_index(&the_index, lock, COMMIT_LOCK))
  		return error(_("Unable to write index."));
  
  	return clean ? 0 : 1;
  }
  
  static void merge_recursive_config(struct merge_options *o)
  {
  	git_config_get_int("merge.verbosity", &o->verbosity);
  	git_config_get_int("diff.renamelimit", &o->diff_rename_limit);
  	git_config_get_int("merge.renamelimit", &o->merge_rename_limit);
  	git_config(git_xmerge_config, NULL);
  }
  
  void init_merge_options(struct merge_options *o)
  {
  	memset(o, 0, sizeof(struct merge_options));
  	o->verbosity = 2;
  	o->buffer_output = 1;
  	o->diff_rename_limit = -1;
  	o->merge_rename_limit = -1;
  	o->renormalize = 0;
  	merge_recursive_config(o);
  	if (getenv("GIT_MERGE_VERBOSITY"))
  		o->verbosity =
  			strtol(getenv("GIT_MERGE_VERBOSITY"), NULL, 10);
  	if (o->verbosity >= 5)
  		o->buffer_output = 0;
  	strbuf_init(&o->obuf, 0);
  	string_list_init(&o->current_file_set, 1);
  	string_list_init(&o->current_directory_set, 1);
  	string_list_init(&o->df_conflict_file_set, 1);
  }
  
  int parse_merge_opt(struct merge_options *o, const char *s)
  {
  	const char *arg;
  
  	if (!s || !*s)
  		return -1;
  	if (!strcmp(s, "ours"))
  		o->recursive_variant = MERGE_RECURSIVE_OURS;
  	else if (!strcmp(s, "theirs"))
  		o->recursive_variant = MERGE_RECURSIVE_THEIRS;
  	else if (!strcmp(s, "subtree"))
  		o->subtree_shift = "";
  	else if (skip_prefix(s, "subtree=", &arg))
  		o->subtree_shift = arg;
  	else if (!strcmp(s, "patience"))
  		o->xdl_opts = DIFF_WITH_ALG(o, PATIENCE_DIFF);
  	else if (!strcmp(s, "histogram"))
  		o->xdl_opts = DIFF_WITH_ALG(o, HISTOGRAM_DIFF);
  	else if (skip_prefix(s, "diff-algorithm=", &arg)) {
  		long value = parse_algorithm_value(arg);
  		if (value < 0)
  			return -1;
  		/* clear out previous settings */
  		DIFF_XDL_CLR(o, NEED_MINIMAL);
  		o->xdl_opts &= ~XDF_DIFF_ALGORITHM_MASK;
  		o->xdl_opts |= value;
  	}
  	else if (!strcmp(s, "ignore-space-change"))
  		o->xdl_opts |= XDF_IGNORE_WHITESPACE_CHANGE;
  	else if (!strcmp(s, "ignore-all-space"))
  		o->xdl_opts |= XDF_IGNORE_WHITESPACE;
  	else if (!strcmp(s, "ignore-space-at-eol"))
  		o->xdl_opts |= XDF_IGNORE_WHITESPACE_AT_EOL;
  	else if (!strcmp(s, "renormalize"))
  		o->renormalize = 1;
  	else if (!strcmp(s, "no-renormalize"))
  		o->renormalize = 0;
  	else if (skip_prefix(s, "rename-threshold=", &arg)) {
  		if ((o->rename_score = parse_rename_score(&arg)) == -1 || *arg != 0)
  			return -1;
  	}
  	else
  		return -1;
  	return 0;
  }
  