merge(3p/git): Merge git upstream at v2.26.2 r/808

1 files changed, 544 insertions, 412 deletions

diff --git a/third_party/git/merge-recursive.c b/third_party/git/merge-recursive.c
index 6b812d67e3ec..7a4e6f20fa8c 100644
--- a/third_party/git/merge-recursive.c
+++ b/third_party/git/merge-recursive.c
@@ -4,30 +4,40 @@
  * The thieves were Alex Riesen and Johannes Schindelin, in June/July 2006
  */
 #include "cache.h"
-#include "config.h"
+#include "merge-recursive.h"
+
 #include "advice.h"
-#include "lockfile.h"
-#include "cache-tree.h"
-#include "object-store.h"
-#include "repository.h"
-#include "commit.h"
+#include "alloc.h"
+#include "attr.h"
 #include "blob.h"
 #include "builtin.h"
-#include "tree-walk.h"
+#include "cache-tree.h"
+#include "commit.h"
+#include "commit-reach.h"
+#include "config.h"
 #include "diff.h"
 #include "diffcore.h"
+#include "dir.h"
+#include "ll-merge.h"
+#include "lockfile.h"
+#include "object-store.h"
+#include "repository.h"
+#include "revision.h"
+#include "string-list.h"
+#include "submodule.h"
 #include "tag.h"
-#include "alloc.h"
+#include "tree-walk.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"
-#include "revision.h"
-#include "commit-reach.h"
+
+struct merge_options_internal {
+	int call_depth;
+	int needed_rename_limit;
+	struct hashmap current_file_dir_set;
+	struct string_list df_conflict_file_set;
+	struct unpack_trees_options unpack_opts;
+	struct index_state orig_index;
+};
 
 struct path_hashmap_entry {
 	struct hashmap_entry e;
@@ -35,14 +45,16 @@ struct path_hashmap_entry {
 };
 
 static int path_hashmap_cmp(const void *cmp_data,
-			    const void *entry,
-			    const void *entry_or_key,
+			    const struct hashmap_entry *eptr,
+			    const struct hashmap_entry *entry_or_key,
 			    const void *keydata)
 {
-	const struct path_hashmap_entry *a = entry;
-	const struct path_hashmap_entry *b = entry_or_key;
+	const struct path_hashmap_entry *a, *b;
 	const char *key = keydata;
 
+	a = container_of(eptr, const struct path_hashmap_entry, e);
+	b = container_of(entry_or_key, const struct path_hashmap_entry, e);
+
 	if (ignore_case)
 		return strcasecmp(a->path, key ? key : b->path);
 	else
@@ -54,6 +66,24 @@ static unsigned int path_hash(const char *path)
 	return ignore_case ? strihash(path) : strhash(path);
 }
 
+/*
+ * For dir_rename_entry, directory names are stored as a full path from the
+ * toplevel of the repository and do not include a trailing '/'.  Also:
+ *
+ *   dir:                original name of directory being renamed
+ *   non_unique_new_dir: if true, could not determine new_dir
+ *   new_dir:            final name of directory being renamed
+ *   possible_new_dirs:  temporary used to help determine new_dir; see comments
+ *                       in get_directory_renames() for details
+ */
+struct dir_rename_entry {
+	struct hashmap_entry ent;
+	char *dir;
+	unsigned non_unique_new_dir:1;
+	struct strbuf new_dir;
+	struct string_list possible_new_dirs;
+};
+
 static struct dir_rename_entry *dir_rename_find_entry(struct hashmap *hashmap,
 						      char *dir)
 {
@@ -61,18 +91,20 @@ static struct dir_rename_entry *dir_rename_find_entry(struct hashmap *hashmap,
 
 	if (dir == NULL)
 		return NULL;
-	hashmap_entry_init(&key, strhash(dir));
+	hashmap_entry_init(&key.ent, strhash(dir));
 	key.dir = dir;
-	return hashmap_get(hashmap, &key, NULL);
+	return hashmap_get_entry(hashmap, &key, ent, NULL);
 }
 
 static int dir_rename_cmp(const void *unused_cmp_data,
-			  const void *entry,
-			  const void *entry_or_key,
+			  const struct hashmap_entry *eptr,
+			  const struct hashmap_entry *entry_or_key,
 			  const void *unused_keydata)
 {
-	const struct dir_rename_entry *e1 = entry;
-	const struct dir_rename_entry *e2 = entry_or_key;
+	const struct dir_rename_entry *e1, *e2;
+
+	e1 = container_of(eptr, const struct dir_rename_entry, ent);
+	e2 = container_of(entry_or_key, const struct dir_rename_entry, ent);
 
 	return strcmp(e1->dir, e2->dir);
 }
@@ -85,34 +117,46 @@ static void dir_rename_init(struct hashmap *map)
 static void dir_rename_entry_init(struct dir_rename_entry *entry,
 				  char *directory)
 {
-	hashmap_entry_init(entry, strhash(directory));
+	hashmap_entry_init(&entry->ent, strhash(directory));
 	entry->dir = directory;
 	entry->non_unique_new_dir = 0;
 	strbuf_init(&entry->new_dir, 0);
 	string_list_init(&entry->possible_new_dirs, 0);
 }
 
+struct collision_entry {
+	struct hashmap_entry ent;
+	char *target_file;
+	struct string_list source_files;
+	unsigned reported_already:1;
+};
+
 static struct collision_entry *collision_find_entry(struct hashmap *hashmap,
 						    char *target_file)
 {
 	struct collision_entry key;
 
-	hashmap_entry_init(&key, strhash(target_file));
+	hashmap_entry_init(&key.ent, strhash(target_file));
 	key.target_file = target_file;
-	return hashmap_get(hashmap, &key, NULL);
+	return hashmap_get_entry(hashmap, &key, ent, NULL);
 }
 
-static int collision_cmp(void *unused_cmp_data,
-			 const struct collision_entry *e1,
-			 const struct collision_entry *e2,
+static int collision_cmp(const void *unused_cmp_data,
+			 const struct hashmap_entry *eptr,
+			 const struct hashmap_entry *entry_or_key,
 			 const void *unused_keydata)
 {
+	const struct collision_entry *e1, *e2;
+
+	e1 = container_of(eptr, const struct collision_entry, ent);
+	e2 = container_of(entry_or_key, const struct collision_entry, ent);
+
 	return strcmp(e1->target_file, e2->target_file);
 }
 
 static void collision_init(struct hashmap *map)
 {
-	hashmap_init(map, (hashmap_cmp_fn) collision_cmp, NULL, 0);
+	hashmap_init(map, collision_cmp, NULL, 0);
 }
 
 static void flush_output(struct merge_options *opt)
@@ -180,17 +224,6 @@ static struct commit *make_virtual_commit(struct repository *repo,
 	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 oid_eq(const struct object_id *a, const struct object_id *b)
-{
-	if (!a && !b)
-		return 2;
-	return a && b && oideq(a, b);
-}
-
 enum rename_type {
 	RENAME_NORMAL = 0,
 	RENAME_VIA_DIR,
@@ -284,7 +317,8 @@ static inline void setup_rename_conflict_info(enum rename_type rename_type,
 
 static int show(struct merge_options *opt, int v)
 {
-	return (!opt->call_depth && opt->verbosity >= v) || opt->verbosity >= 5;
+	return (!opt->priv->call_depth && opt->verbosity >= v) ||
+		opt->verbosity >= 5;
 }
 
 __attribute__((format (printf, 3, 4)))
@@ -295,7 +329,7 @@ static void output(struct merge_options *opt, int v, const char *fmt, ...)
 	if (!show(opt, v))
 		return;
 
-	strbuf_addchars(&opt->obuf, ' ', opt->call_depth * 2);
+	strbuf_addchars(&opt->obuf, ' ', opt->priv->call_depth * 2);
 
 	va_start(ap, fmt);
 	strbuf_vaddf(&opt->obuf, fmt, ap);
@@ -310,7 +344,7 @@ static void output_commit_title(struct merge_options *opt, struct commit *commit
 {
 	struct merge_remote_desc *desc;
 
-	strbuf_addchars(&opt->obuf, ' ', opt->call_depth * 2);
+	strbuf_addchars(&opt->obuf, ' ', opt->priv->call_depth * 2);
 	desc = merge_remote_util(commit);
 	if (desc)
 		strbuf_addf(&opt->obuf, "virtual %s\n", desc->name);
@@ -358,6 +392,11 @@ static int add_cacheinfo(struct merge_options *opt,
 	return ret;
 }
 
+static inline int merge_detect_rename(struct merge_options *opt)
+{
+	return (opt->detect_renames >= 0) ? opt->detect_renames : 1;
+}
+
 static void init_tree_desc_from_tree(struct tree_desc *desc, struct tree *tree)
 {
 	parse_tree(tree);
@@ -373,74 +412,43 @@ static int unpack_trees_start(struct merge_options *opt,
 	struct tree_desc t[3];
 	struct index_state tmp_index = { NULL };
 
-	memset(&opt->unpack_opts, 0, sizeof(opt->unpack_opts));
-	if (opt->call_depth)
-		opt->unpack_opts.index_only = 1;
+	memset(&opt->priv->unpack_opts, 0, sizeof(opt->priv->unpack_opts));
+	if (opt->priv->call_depth)
+		opt->priv->unpack_opts.index_only = 1;
 	else
-		opt->unpack_opts.update = 1;
-	opt->unpack_opts.merge = 1;
-	opt->unpack_opts.head_idx = 2;
-	opt->unpack_opts.fn = threeway_merge;
-	opt->unpack_opts.src_index = opt->repo->index;
-	opt->unpack_opts.dst_index = &tmp_index;
-	opt->unpack_opts.aggressive = !merge_detect_rename(opt);
-	setup_unpack_trees_porcelain(&opt->unpack_opts, "merge");
+		opt->priv->unpack_opts.update = 1;
+	opt->priv->unpack_opts.merge = 1;
+	opt->priv->unpack_opts.head_idx = 2;
+	opt->priv->unpack_opts.fn = threeway_merge;
+	opt->priv->unpack_opts.src_index = opt->repo->index;
+	opt->priv->unpack_opts.dst_index = &tmp_index;
+	opt->priv->unpack_opts.aggressive = !merge_detect_rename(opt);
+	setup_unpack_trees_porcelain(&opt->priv->unpack_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, &opt->unpack_opts);
+	rc = unpack_trees(3, t, &opt->priv->unpack_opts);
 	cache_tree_free(&opt->repo->index->cache_tree);
 
 	/*
-	 * Update opt->repo->index to match the new results, AFTER saving a copy
-	 * in opt->orig_index.  Update src_index to point to the saved copy.
-	 * (verify_uptodate() checks src_index, and the original index is
-	 * the one that had the necessary modification timestamps.)
+	 * Update opt->repo->index to match the new results, AFTER saving a
+	 * copy in opt->priv->orig_index.  Update src_index to point to the
+	 * saved copy.  (verify_uptodate() checks src_index, and the original
+	 * index is the one that had the necessary modification timestamps.)
 	 */
-	opt->orig_index = *opt->repo->index;
+	opt->priv->orig_index = *opt->repo->index;
 	*opt->repo->index = tmp_index;
-	opt->unpack_opts.src_index = &opt->orig_index;
+	opt->priv->unpack_opts.src_index = &opt->priv->orig_index;
 
 	return rc;
 }
 
 static void unpack_trees_finish(struct merge_options *opt)
 {
-	discard_index(&opt->orig_index);
-	clear_unpack_trees_porcelain(&opt->unpack_opts);
-}
-
-struct tree *write_tree_from_memory(struct merge_options *opt)
-{
-	struct tree *result = NULL;
-	struct index_state *istate = opt->repo->index;
-
-	if (unmerged_index(istate)) {
-		int i;
-		fprintf(stderr, "BUG: There are unmerged index entries:\n");
-		for (i = 0; i < istate->cache_nr; i++) {
-			const struct cache_entry *ce = istate->cache[i];
-			if (ce_stage(ce))
-				fprintf(stderr, "BUG: %d %.*s\n", ce_stage(ce),
-					(int)ce_namelen(ce), ce->name);
-		}
-		BUG("unmerged index entries in merge-recursive.c");
-	}
-
-	if (!istate->cache_tree)
-		istate->cache_tree = cache_tree();
-
-	if (!cache_tree_fully_valid(istate->cache_tree) &&
-	    cache_tree_update(istate, 0) < 0) {
-		err(opt, _("error building trees"));
-		return NULL;
-	}
-
-	result = lookup_tree(opt->repo, &istate->cache_tree->oid);
-
-	return result;
+	discard_index(&opt->priv->orig_index);
+	clear_unpack_trees_porcelain(&opt->priv->unpack_opts);
 }
 
 static int save_files_dirs(const struct object_id *oid,
@@ -454,8 +462,8 @@ static int save_files_dirs(const struct object_id *oid,
 	strbuf_addstr(base, path);
 
 	FLEX_ALLOC_MEM(entry, path, base->buf, base->len);
-	hashmap_entry_init(entry, path_hash(entry->path));
-	hashmap_add(&opt->current_file_dir_set, entry);
+	hashmap_entry_init(&entry->e, path_hash(entry->path));
+	hashmap_add(&opt->priv->current_file_dir_set, &entry->e);
 
 	strbuf_setlen(base, baselen);
 	return (S_ISDIR(mode) ? READ_TREE_RECURSIVE : 0);
@@ -586,7 +594,7 @@ static void record_df_conflict_files(struct merge_options *opt,
 	 * If we're merging merge-bases, we don't want to bother with
 	 * any working directory changes.
 	 */
-	if (opt->call_depth)
+	if (opt->priv->call_depth)
 		return;
 
 	/* Ensure D/F conflicts are adjacent in the entries list. */
@@ -598,7 +606,7 @@ static void record_df_conflict_files(struct merge_options *opt,
 	df_sorted_entries.cmp = string_list_df_name_compare;
 	string_list_sort(&df_sorted_entries);
 
-	string_list_clear(&opt->df_conflict_file_set, 1);
+	string_list_clear(&opt->priv->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);
@@ -614,7 +622,7 @@ static void record_df_conflict_files(struct merge_options *opt,
 		    len > last_len &&
 		    memcmp(path, last_file, last_len) == 0 &&
 		    path[last_len] == '/') {
-			string_list_insert(&opt->df_conflict_file_set, last_file);
+			string_list_insert(&opt->priv->df_conflict_file_set, last_file);
 		}
 
 		/*
@@ -681,8 +689,8 @@ static void update_entry(struct stage_data *entry,
 static int remove_file(struct merge_options *opt, int clean,
 		       const char *path, int no_wd)
 {
-	int update_cache = opt->call_depth || clean;
-	int update_working_directory = !opt->call_depth && !no_wd;
+	int update_cache = opt->priv->call_depth || clean;
+	int update_working_directory = !opt->priv->call_depth && !no_wd;
 
 	if (update_cache) {
 		if (remove_file_from_index(opt->repo->index, path))
@@ -712,7 +720,9 @@ static void add_flattened_path(struct strbuf *out, const char *s)
 			out->buf[i] = '_';
 }
 
-static char *unique_path(struct merge_options *opt, const char *path, const char *branch)
+static char *unique_path(struct merge_options *opt,
+			 const char *path,
+			 const char *branch)
 {
 	struct path_hashmap_entry *entry;
 	struct strbuf newpath = STRBUF_INIT;
@@ -723,16 +733,16 @@ static char *unique_path(struct merge_options *opt, const char *path, const char
 	add_flattened_path(&newpath, branch);
 
 	base_len = newpath.len;
-	while (hashmap_get_from_hash(&opt->current_file_dir_set,
+	while (hashmap_get_from_hash(&opt->priv->current_file_dir_set,
 				     path_hash(newpath.buf), newpath.buf) ||
-	       (!opt->call_depth && file_exists(newpath.buf))) {
+	       (!opt->priv->call_depth && file_exists(newpath.buf))) {
 		strbuf_setlen(&newpath, base_len);
 		strbuf_addf(&newpath, "_%d", suffix++);
 	}
 
 	FLEX_ALLOC_MEM(entry, path, newpath.buf, newpath.len);
-	hashmap_entry_init(entry, path_hash(entry->path));
-	hashmap_add(&opt->current_file_dir_set, entry);
+	hashmap_entry_init(&entry->e, path_hash(entry->path));
+	hashmap_add(&opt->priv->current_file_dir_set, &entry->e);
 	return strbuf_detach(&newpath, NULL);
 }
 
@@ -764,7 +774,8 @@ static int dir_in_way(struct index_state *istate, const char *path,
 
 	strbuf_release(&dirpath);
 	return check_working_copy && !lstat(path, &st) && S_ISDIR(st.st_mode) &&
-		!(empty_ok && is_empty_dir(path));
+		!(empty_ok && is_empty_dir(path)) &&
+		!has_symlink_leading_path(path, strlen(path));
 }
 
 /*
@@ -774,7 +785,7 @@ static int dir_in_way(struct index_state *istate, const char *path,
 static int was_tracked_and_matches(struct merge_options *opt, const char *path,
 				   const struct diff_filespec *blob)
 {
-	int pos = index_name_pos(&opt->orig_index, path, strlen(path));
+	int pos = index_name_pos(&opt->priv->orig_index, path, strlen(path));
 	struct cache_entry *ce;
 
 	if (0 > pos)
@@ -782,8 +793,8 @@ static int was_tracked_and_matches(struct merge_options *opt, const char *path,
 		return 0;
 
 	/* See if the file we were tracking before matches */
-	ce = opt->orig_index.cache[pos];
-	return (oid_eq(&ce->oid, &blob->oid) && ce->ce_mode == blob->mode);
+	ce = opt->priv->orig_index.cache[pos];
+	return (oideq(&ce->oid, &blob->oid) && ce->ce_mode == blob->mode);
 }
 
 /*
@@ -791,7 +802,7 @@ static int was_tracked_and_matches(struct merge_options *opt, const char *path,
  */
 static int was_tracked(struct merge_options *opt, const char *path)
 {
-	int pos = index_name_pos(&opt->orig_index, path, strlen(path));
+	int pos = index_name_pos(&opt->priv->orig_index, path, strlen(path));
 
 	if (0 <= pos)
 		/* we were tracking this path before the merge */
@@ -848,12 +859,12 @@ static int was_dirty(struct merge_options *opt, const char *path)
 	struct cache_entry *ce;
 	int dirty = 1;
 
-	if (opt->call_depth || !was_tracked(opt, path))
+	if (opt->priv->call_depth || !was_tracked(opt, path))
 		return !dirty;
 
-	ce = index_file_exists(opt->unpack_opts.src_index,
+	ce = index_file_exists(opt->priv->unpack_opts.src_index,
 			       path, strlen(path), ignore_case);
-	dirty = verify_uptodate(ce, &opt->unpack_opts) != 0;
+	dirty = verify_uptodate(ce, &opt->priv->unpack_opts) != 0;
 	return dirty;
 }
 
@@ -863,8 +874,8 @@ static int make_room_for_path(struct merge_options *opt, const char *path)
 	const char *msg = _("failed to create path '%s'%s");
 
 	/* Unlink any D/F conflict files that are in the way */
-	for (i = 0; i < opt->df_conflict_file_set.nr; i++) {
-		const char *df_path = opt->df_conflict_file_set.items[i].string;
+	for (i = 0; i < opt->priv->df_conflict_file_set.nr; i++) {
+		const char *df_path = opt->priv->df_conflict_file_set.items[i].string;
 		size_t pathlen = strlen(path);
 		size_t df_pathlen = strlen(df_path);
 		if (df_pathlen < pathlen &&
@@ -874,7 +885,7 @@ static int make_room_for_path(struct merge_options *opt, const char *path)
 			       _("Removing %s to make room for subdirectory\n"),
 			       df_path);
 			unlink(df_path);
-			unsorted_string_list_delete_item(&opt->df_conflict_file_set,
+			unsorted_string_list_delete_item(&opt->priv->df_conflict_file_set,
 							 i, 0);
 			break;
 		}
@@ -915,7 +926,7 @@ static int update_file_flags(struct merge_options *opt,
 {
 	int ret = 0;
 
-	if (opt->call_depth)
+	if (opt->priv->call_depth)
 		update_wd = 0;
 
 	if (update_wd) {
@@ -934,9 +945,11 @@ static int update_file_flags(struct merge_options *opt,
 		}
 
 		buf = read_object_file(&contents->oid, &type, &size);
-		if (!buf)
-			return err(opt, _("cannot read object %s '%s'"),
-				   oid_to_hex(&contents->oid), path);
+		if (!buf) {
+			ret = err(opt, _("cannot read object %s '%s'"),
+				  oid_to_hex(&contents->oid), path);
+			goto free_buf;
+		}
 		if (type != OBJ_BLOB) {
 			ret = err(opt, _("blob expected for %s '%s'"),
 				  oid_to_hex(&contents->oid), path);
@@ -944,7 +957,8 @@ static int update_file_flags(struct merge_options *opt,
 		}
 		if (S_ISREG(contents->mode)) {
 			struct strbuf strbuf = STRBUF_INIT;
-			if (convert_to_working_tree(opt->repo->index, path, buf, size, &strbuf)) {
+			if (convert_to_working_tree(opt->repo->index,
+						    path, buf, size, &strbuf)) {
 				free(buf);
 				size = strbuf.len;
 				buf = strbuf_detach(&strbuf, NULL);
@@ -984,10 +998,13 @@ static int update_file_flags(struct merge_options *opt,
 		free(buf);
 	}
 update_index:
-	if (!ret && update_cache)
-		if (add_cacheinfo(opt, contents, path, 0, update_wd,
+	if (!ret && update_cache) {
+		int refresh = (!opt->priv->call_depth &&
+			       contents->mode != S_IFGITLINK);
+		if (add_cacheinfo(opt, contents, path, 0, refresh,
 				  ADD_CACHE_OK_TO_ADD))
 			return -1;
+	}
 	return ret;
 }
 
@@ -997,7 +1014,7 @@ static int update_file(struct merge_options *opt,
 		       const char *path)
 {
 	return update_file_flags(opt, contents, path,
-				 opt->call_depth || clean, !opt->call_depth);
+				 opt->priv->call_depth || clean, !opt->priv->call_depth);
 }
 
 /* Low level file merging, update and removal */
@@ -1019,22 +1036,22 @@ static int merge_3way(struct merge_options *opt,
 {
 	mmfile_t orig, src1, src2;
 	struct ll_merge_options ll_opts = {0};
-	char *base_name, *name1, *name2;
+	char *base, *name1, *name2;
 	int merge_status;
 
 	ll_opts.renormalize = opt->renormalize;
 	ll_opts.extra_marker_size = extra_marker_size;
 	ll_opts.xdl_opts = opt->xdl_opts;
 
-	if (opt->call_depth) {
+	if (opt->priv->call_depth) {
 		ll_opts.virtual_ancestor = 1;
 		ll_opts.variant = 0;
 	} else {
 		switch (opt->recursive_variant) {
-		case MERGE_RECURSIVE_OURS:
+		case MERGE_VARIANT_OURS:
 			ll_opts.variant = XDL_MERGE_FAVOR_OURS;
 			break;
-		case MERGE_RECURSIVE_THEIRS:
+		case MERGE_VARIANT_THEIRS:
 			ll_opts.variant = XDL_MERGE_FAVOR_THEIRS;
 			break;
 		default:
@@ -1043,16 +1060,13 @@ static int merge_3way(struct merge_options *opt,
 		}
 	}
 
-	assert(a->path && b->path);
-	if (strcmp(a->path, b->path) ||
-	    (opt->ancestor != NULL && strcmp(a->path, o->path) != 0)) {
-		base_name = opt->ancestor == NULL ? NULL :
-			mkpathdup("%s:%s", opt->ancestor, o->path);
+	assert(a->path && b->path && o->path && opt->ancestor);
+	if (strcmp(a->path, b->path) || strcmp(a->path, o->path) != 0) {
+		base  = mkpathdup("%s:%s", opt->ancestor, o->path);
 		name1 = mkpathdup("%s:%s", branch1, a->path);
 		name2 = mkpathdup("%s:%s", branch2, b->path);
 	} else {
-		base_name = opt->ancestor == NULL ? NULL :
-			mkpathdup("%s", opt->ancestor);
+		base  = mkpathdup("%s", opt->ancestor);
 		name1 = mkpathdup("%s", branch1);
 		name2 = mkpathdup("%s", branch2);
 	}
@@ -1061,11 +1075,11 @@ static int merge_3way(struct merge_options *opt,
 	read_mmblob(&src1, &a->oid);
 	read_mmblob(&src2, &b->oid);
 
-	merge_status = ll_merge(result_buf, a->path, &orig, base_name,
+	merge_status = ll_merge(result_buf, a->path, &orig, base,
 				&src1, name1, &src2, name2,
 				opt->repo->index, &ll_opts);
 
-	free(base_name);
+	free(base);
 	free(name1);
 	free(name2);
 	free(orig.ptr);
@@ -1160,7 +1174,7 @@ static int merge_submodule(struct merge_options *opt,
 	struct object_array merges;
 
 	int i;
-	int search = !opt->call_depth;
+	int search = !opt->priv->call_depth;
 
 	/* store a in result in case we fail */
 	oidcpy(result, a);
@@ -1295,7 +1309,7 @@ static int merge_mode_and_contents(struct merge_options *opt,
 			oidcpy(&result->blob.oid, &b->oid);
 		}
 	} else {
-		if (!oid_eq(&a->oid, &o->oid) && !oid_eq(&b->oid, &o->oid))
+		if (!oideq(&a->oid, &o->oid) && !oideq(&b->oid, &o->oid))
 			result->merge = 1;
 
 		/*
@@ -1311,9 +1325,9 @@ static int merge_mode_and_contents(struct merge_options *opt,
 			}
 		}
 
-		if (oid_eq(&a->oid, &b->oid) || oid_eq(&a->oid, &o->oid))
+		if (oideq(&a->oid, &b->oid) || oideq(&a->oid, &o->oid))
 			oidcpy(&result->blob.oid, &b->oid);
-		else if (oid_eq(&b->oid, &o->oid))
+		else if (oideq(&b->oid, &o->oid))
 			oidcpy(&result->blob.oid, &a->oid);
 		else if (S_ISREG(a->mode)) {
 			mmbuffer_t result_buf;
@@ -1344,15 +1358,15 @@ static int merge_mode_and_contents(struct merge_options *opt,
 							&b->oid);
 		} else if (S_ISLNK(a->mode)) {
 			switch (opt->recursive_variant) {
-			case MERGE_RECURSIVE_NORMAL:
+			case MERGE_VARIANT_NORMAL:
 				oidcpy(&result->blob.oid, &a->oid);
-				if (!oid_eq(&a->oid, &b->oid))
+				if (!oideq(&a->oid, &b->oid))
 					result->clean = 0;
 				break;
-			case MERGE_RECURSIVE_OURS:
+			case MERGE_VARIANT_OURS:
 				oidcpy(&result->blob.oid, &a->oid);
 				break;
-			case MERGE_RECURSIVE_THEIRS:
+			case MERGE_VARIANT_THEIRS:
 				oidcpy(&result->blob.oid, &b->oid);
 				break;
 			}
@@ -1378,10 +1392,11 @@ static int handle_rename_via_dir(struct merge_options *opt,
 	const struct rename *ren = ci->ren1;
 	const struct diff_filespec *dest = ren->pair->two;
 	char *file_path = dest->path;
-	int mark_conflicted = (opt->detect_directory_renames == 1);
+	int mark_conflicted = (opt->detect_directory_renames ==
+			       MERGE_DIRECTORY_RENAMES_CONFLICT);
 	assert(ren->dir_rename_original_dest);
 
-	if (!opt->call_depth && would_lose_untracked(opt, dest->path)) {
+	if (!opt->priv->call_depth && would_lose_untracked(opt, dest->path)) {
 		mark_conflicted = 1;
 		file_path = unique_path(opt, dest->path, ren->branch);
 		output(opt, 1, _("Error: Refusing to lose untracked file at %s; "
@@ -1424,12 +1439,12 @@ static int handle_change_delete(struct merge_options *opt,
 	const char *update_path = path;
 	int ret = 0;
 
-	if (dir_in_way(opt->repo->index, path, !opt->call_depth, 0) ||
-	    (!opt->call_depth && would_lose_untracked(opt, path))) {
+	if (dir_in_way(opt->repo->index, path, !opt->priv->call_depth, 0) ||
+	    (!opt->priv->call_depth && would_lose_untracked(opt, path))) {
 		update_path = alt_path = unique_path(opt, path, change_branch);
 	}
 
-	if (opt->call_depth) {
+	if (opt->priv->call_depth) {
 		/*
 		 * We cannot arbitrarily accept either a_sha or b_sha as
 		 * correct; since there is no true "middle point" between
@@ -1504,14 +1519,14 @@ static int handle_rename_delete(struct merge_options *opt,
 				     opt->branch2 : opt->branch1);
 
 	if (handle_change_delete(opt,
-				 opt->call_depth ? orig->path : dest->path,
-				 opt->call_depth ? NULL : orig->path,
+				 opt->priv->call_depth ? orig->path : dest->path,
+				 opt->priv->call_depth ? NULL : orig->path,
 				 orig, dest,
 				 rename_branch, delete_branch,
 				 _("rename"), _("renamed")))
 		return -1;
 
-	if (opt->call_depth)
+	if (opt->priv->call_depth)
 		return remove_file_from_index(opt->repo->index, dest->path);
 	else
 		return update_stages(opt, dest->path, NULL,
@@ -1545,42 +1560,13 @@ static int handle_file_collision(struct merge_options *opt,
 					     b, a);
 	}
 
-	/*
-	 * In the recursive case, we just opt to undo renames
-	 */
-	if (opt->call_depth && (prev_path1 || prev_path2)) {
-		/* Put first file (a->oid, a->mode) in its original spot */
-		if (prev_path1) {
-			if (update_file(opt, 1, a, prev_path1))
-				return -1;
-		} else {
-			if (update_file(opt, 1, a, collide_path))
-				return -1;
-		}
-
-		/* Put second file (b->oid, b->mode) in its original spot */
-		if (prev_path2) {
-			if (update_file(opt, 1, b, prev_path2))
-				return -1;
-		} else {
-			if (update_file(opt, 1, b, collide_path))
-				return -1;
-		}
-
-		/* Don't leave something at collision path if unrenaming both */
-		if (prev_path1 && prev_path2)
-			remove_file(opt, 1, collide_path, 0);
-
-		return 0;
-	}
-
 	/* Remove rename sources if rename/add or rename/rename(2to1) */
 	if (prev_path1)
 		remove_file(opt, 1, prev_path1,
-			    opt->call_depth || would_lose_untracked(opt, prev_path1));
+			    opt->priv->call_depth || would_lose_untracked(opt, prev_path1));
 	if (prev_path2)
 		remove_file(opt, 1, prev_path2,
-			    opt->call_depth || would_lose_untracked(opt, prev_path2));
+			    opt->priv->call_depth || would_lose_untracked(opt, prev_path2));
 
 	/*
 	 * Remove the collision path, if it wouldn't cause dirty contents
@@ -1622,12 +1608,12 @@ static int handle_file_collision(struct merge_options *opt,
 	null.mode = 0;
 
 	if (merge_mode_and_contents(opt, &null, a, b, collide_path,
-				    branch1, branch2, opt->call_depth * 2, &mfi))
+				    branch1, branch2, opt->priv->call_depth * 2, &mfi))
 		return -1;
 	mfi.clean &= !alt_path;
 	if (update_file(opt, mfi.clean, &mfi.blob, update_path))
 		return -1;
-	if (!mfi.clean && !opt->call_depth &&
+	if (!mfi.clean && !opt->priv->call_depth &&
 	    update_stages(opt, collide_path, NULL, a, b))
 		return -1;
 	free(alt_path);
@@ -1667,7 +1653,7 @@ static int handle_rename_add(struct merge_options *opt,
 				    &ci->ren1->src_entry->stages[other_stage],
 				    prev_path_desc,
 				    opt->branch1, opt->branch2,
-				    1 + opt->call_depth * 2, &mfi))
+				    1 + opt->priv->call_depth * 2, &mfi))
 		return -1;
 	free(prev_path_desc);
 
@@ -1685,7 +1671,7 @@ static char *find_path_for_conflict(struct merge_options *opt,
 				    const char *branch2)
 {
 	char *new_path = NULL;
-	if (dir_in_way(opt->repo->index, path, !opt->call_depth, 0)) {
+	if (dir_in_way(opt->repo->index, path, !opt->priv->call_depth, 0)) {
 		new_path = unique_path(opt, path, branch1);
 		output(opt, 1, _("%s is a directory in %s adding "
 			       "as %s instead"),
@@ -1700,6 +1686,14 @@ static char *find_path_for_conflict(struct merge_options *opt,
 	return new_path;
 }
 
+/*
+ * Toggle the stage number between "ours" and "theirs" (2 and 3).
+ */
+static inline int flip_stage(int stage)
+{
+	return (2 + 3) - stage;
+}
+
 static int handle_rename_rename_1to2(struct merge_options *opt,
 				     struct rename_conflict_info *ci)
 {
@@ -1716,95 +1710,66 @@ static int handle_rename_rename_1to2(struct merge_options *opt,
 	       "rename \"%s\"->\"%s\" in \"%s\"%s"),
 	       o->path, a->path, ci->ren1->branch,
 	       o->path, b->path, ci->ren2->branch,
-	       opt->call_depth ? _(" (left unresolved)") : "");
+	       opt->priv->call_depth ? _(" (left unresolved)") : "");
 
 	path_desc = xstrfmt("%s and %s, both renamed from %s",
 			    a->path, b->path, o->path);
 	if (merge_mode_and_contents(opt, o, a, b, path_desc,
 				    ci->ren1->branch, ci->ren2->branch,
-				    opt->call_depth * 2, &mfi))
+				    opt->priv->call_depth * 2, &mfi))
 		return -1;
 	free(path_desc);
 
-	if (opt->call_depth) {
-		/*
-		 * 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.
-		 */
-		if (update_file(opt, 0, &mfi.blob, o->path))
-			return -1;
+	if (opt->priv->call_depth)
+		remove_file_from_index(opt->repo->index, o->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 = &ci->ren1->dst_entry->stages[2 ^ 1];
-		if (is_valid(add)) {
-			if (update_file(opt, 0, add, a->path))
-				return -1;
-		}
-		else
-			remove_file_from_index(opt->repo->index, a->path);
-		add = &ci->ren2->dst_entry->stages[3 ^ 1];
-		if (is_valid(add)) {
-			if (update_file(opt, 0, add, b->path))
-				return -1;
-		}
-		else
-			remove_file_from_index(opt->repo->index, b->path);
+	/*
+	 * For each destination path, we need to see if there is a
+	 * rename/add collision.  If not, we can write the file out
+	 * to the specified location.
+	 */
+	add = &ci->ren1->dst_entry->stages[flip_stage(2)];
+	if (is_valid(add)) {
+		add->path = mfi.blob.path = a->path;
+		if (handle_file_collision(opt, a->path,
+					  NULL, NULL,
+					  ci->ren1->branch,
+					  ci->ren2->branch,
+					  &mfi.blob, add) < 0)
+			return -1;
 	} else {
-		/*
-		 * For each destination path, we need to see if there is a
-		 * rename/add collision.  If not, we can write the file out
-		 * to the specified location.
-		 */
-		add = &ci->ren1->dst_entry->stages[2 ^ 1];
-		if (is_valid(add)) {
-			add->path = mfi.blob.path = a->path;
-			if (handle_file_collision(opt, a->path,
-						  NULL, NULL,
-						  ci->ren1->branch,
-						  ci->ren2->branch,
-						  &mfi.blob, add) < 0)
-				return -1;
-		} else {
-			char *new_path = find_path_for_conflict(opt, a->path,
-								ci->ren1->branch,
-								ci->ren2->branch);
-			if (update_file(opt, 0, &mfi.blob,
-					new_path ? new_path : a->path))
-				return -1;
-			free(new_path);
-			if (update_stages(opt, a->path, NULL, a, NULL))
-				return -1;
-		}
+		char *new_path = find_path_for_conflict(opt, a->path,
+							ci->ren1->branch,
+							ci->ren2->branch);
+		if (update_file(opt, 0, &mfi.blob,
+				new_path ? new_path : a->path))
+			return -1;
+		free(new_path);
+		if (!opt->priv->call_depth &&
+		    update_stages(opt, a->path, NULL, a, NULL))
+			return -1;
+	}
 
-		add = &ci->ren2->dst_entry->stages[3 ^ 1];
-		if (is_valid(add)) {
-			add->path = mfi.blob.path = b->path;
-			if (handle_file_collision(opt, b->path,
-						  NULL, NULL,
-						  ci->ren1->branch,
-						  ci->ren2->branch,
-						  add, &mfi.blob) < 0)
-				return -1;
-		} else {
-			char *new_path = find_path_for_conflict(opt, b->path,
-								ci->ren2->branch,
-								ci->ren1->branch);
-			if (update_file(opt, 0, &mfi.blob,
-					new_path ? new_path : b->path))
-				return -1;
-			free(new_path);
-			if (update_stages(opt, b->path, NULL, NULL, b))
-				return -1;
-		}
+	add = &ci->ren2->dst_entry->stages[flip_stage(3)];
+	if (is_valid(add)) {
+		add->path = mfi.blob.path = b->path;
+		if (handle_file_collision(opt, b->path,
+					  NULL, NULL,
+					  ci->ren1->branch,
+					  ci->ren2->branch,
+					  add, &mfi.blob) < 0)
+			return -1;
+	} else {
+		char *new_path = find_path_for_conflict(opt, b->path,
+							ci->ren2->branch,
+							ci->ren1->branch);
+		if (update_file(opt, 0, &mfi.blob,
+				new_path ? new_path : b->path))
+			return -1;
+		free(new_path);
+		if (!opt->priv->call_depth &&
+		    update_stages(opt, b->path, NULL, NULL, b))
+			return -1;
 	}
 
 	return 0;
@@ -1834,19 +1799,19 @@ static int handle_rename_rename_2to1(struct merge_options *opt,
 	path_side_1_desc = xstrfmt("version of %s from %s", path, a->path);
 	path_side_2_desc = xstrfmt("version of %s from %s", path, b->path);
 	ostage1 = ci->ren1->branch == opt->branch1 ? 3 : 2;
-	ostage2 = ostage1 ^ 1;
+	ostage2 = flip_stage(ostage1);
 	ci->ren1->src_entry->stages[ostage1].path = a->path;
 	ci->ren2->src_entry->stages[ostage2].path = b->path;
 	if (merge_mode_and_contents(opt, a, c1,
 				    &ci->ren1->src_entry->stages[ostage1],
 				    path_side_1_desc,
 				    opt->branch1, opt->branch2,
-				    1 + opt->call_depth * 2, &mfi_c1) ||
+				    1 + opt->priv->call_depth * 2, &mfi_c1) ||
 	    merge_mode_and_contents(opt, b,
 				    &ci->ren2->src_entry->stages[ostage2],
 				    c2, path_side_2_desc,
 				    opt->branch1, opt->branch2,
-				    1 + opt->call_depth * 2, &mfi_c2))
+				    1 + opt->priv->call_depth * 2, &mfi_c2))
 		return -1;
 	free(path_side_1_desc);
 	free(path_side_2_desc);
@@ -1880,17 +1845,15 @@ static struct diff_queue_struct *get_diffpairs(struct merge_options *opt,
 	 */
 	if (opts.detect_rename > DIFF_DETECT_RENAME)
 		opts.detect_rename = DIFF_DETECT_RENAME;
-	opts.rename_limit = opt->merge_rename_limit >= 0 ? opt->merge_rename_limit :
-			    opt->diff_rename_limit >= 0 ? opt->diff_rename_limit :
-			    1000;
+	opts.rename_limit = (opt->rename_limit >= 0) ? opt->rename_limit : 1000;
 	opts.rename_score = opt->rename_score;
 	opts.show_rename_progress = opt->show_rename_progress;
 	opts.output_format = DIFF_FORMAT_NO_OUTPUT;
 	diff_setup_done(&opts);
 	diff_tree_oid(&o_tree->object.oid, &tree->object.oid, "", &opts);
 	diffcore_std(&opts);
-	if (opts.needed_rename_limit > opt->needed_rename_limit)
-		opt->needed_rename_limit = opts.needed_rename_limit;
+	if (opts.needed_rename_limit > opt->priv->needed_rename_limit)
+		opt->priv->needed_rename_limit = opts.needed_rename_limit;
 
 	ret = xmalloc(sizeof(*ret));
 	*ret = diff_queued_diff;
@@ -1930,6 +1893,16 @@ static char *apply_dir_rename(struct dir_rename_entry *entry,
 		return NULL;
 
 	oldlen = strlen(entry->dir);
+	if (entry->new_dir.len == 0)
+		/*
+		 * If someone renamed/merged a subdirectory into the root
+		 * directory (e.g. 'some/subdir' -> ''), then we want to
+		 * avoid returning
+		 *     '' + '/filename'
+		 * as the rename; we need to make old_path + oldlen advance
+		 * past the '/' character.
+		 */
+		oldlen++;
 	newlen = entry->new_dir.len + (strlen(old_path) - oldlen) + 1;
 	strbuf_grow(&new_path, newlen);
 	strbuf_addbuf(&new_path, &entry->new_dir);
@@ -1942,8 +1915,8 @@ static void get_renamed_dir_portion(const char *old_path, const char *new_path,
 				    char **old_dir, char **new_dir)
 {
 	char *end_of_old, *end_of_new;
-	int old_len, new_len;
 
+	/* Default return values: NULL, meaning no rename */
 	*old_dir = NULL;
 	*new_dir = NULL;
 
@@ -1954,43 +1927,91 @@ static void get_renamed_dir_portion(const char *old_path, const char *new_path,
 	 *    "a/b/c/d" was renamed to "a/b/some/thing/else"
 	 * so, for this example, this function returns "a/b/c/d" in
 	 * *old_dir and "a/b/some/thing/else" in *new_dir.
-	 *
-	 * Also, if the basename of the file changed, we don't care.  We
-	 * want to know which portion of the directory, if any, changed.
+	 */
+
+	/*
+	 * If the basename of the file changed, we don't care.  We want
+	 * to know which portion of the directory, if any, changed.
 	 */
 	end_of_old = strrchr(old_path, '/');
 	end_of_new = strrchr(new_path, '/');
 
-	if (end_of_old == NULL || end_of_new == NULL)
+	/*
+	 * If end_of_old is NULL, old_path wasn't in a directory, so there
+	 * could not be a directory rename (our rule elsewhere that a
+	 * directory which still exists is not considered to have been
+	 * renamed means the root directory can never be renamed -- because
+	 * the root directory always exists).
+	 */
+	if (end_of_old == NULL)
+		return; /* Note: *old_dir and *new_dir are still NULL */
+
+	/*
+	 * If new_path contains no directory (end_of_new is NULL), then we
+	 * have a rename of old_path's directory to the root directory.
+	 */
+	if (end_of_new == NULL) {
+		*old_dir = xstrndup(old_path, end_of_old - old_path);
+		*new_dir = xstrdup("");
 		return;
+	}
+
+	/* Find the first non-matching character traversing backwards */
 	while (*--end_of_new == *--end_of_old &&
 	       end_of_old != old_path &&
 	       end_of_new != new_path)
 		; /* Do nothing; all in the while loop */
+
 	/*
-	 * We've found the first non-matching character in the directory
-	 * paths.  That means the current directory we were comparing
-	 * represents the rename.  Move end_of_old and end_of_new back
-	 * to the full directory name.
+	 * If both got back to the beginning of their strings, then the
+	 * directory didn't change at all, only the basename did.
 	 */
-	if (*end_of_old == '/')
-		end_of_old++;
-	if (*end_of_old != '/')
-		end_of_new++;
-	end_of_old = strchr(end_of_old, '/');
-	end_of_new = strchr(end_of_new, '/');
+	if (end_of_old == old_path && end_of_new == new_path &&
+	    *end_of_old == *end_of_new)
+		return; /* Note: *old_dir and *new_dir are still NULL */
 
 	/*
-	 * It may have been the case that old_path and new_path were the same
-	 * directory all along.  Don't claim a rename if they're the same.
+	 * If end_of_new got back to the beginning of its string, and
+	 * end_of_old got back to the beginning of some subdirectory, then
+	 * we have a rename/merge of a subdirectory into the root, which
+	 * needs slightly special handling.
+	 *
+	 * Note: There is no need to consider the opposite case, with a
+	 * rename/merge of the root directory into some subdirectory
+	 * because as noted above the root directory always exists so it
+	 * cannot be considered to be renamed.
 	 */
-	old_len = end_of_old - old_path;
-	new_len = end_of_new - new_path;
-
-	if (old_len != new_len || strncmp(old_path, new_path, old_len)) {
-		*old_dir = xstrndup(old_path, old_len);
-		*new_dir = xstrndup(new_path, new_len);
+	if (end_of_new == new_path &&
+	    end_of_old != old_path && end_of_old[-1] == '/') {
+		*old_dir = xstrndup(old_path, --end_of_old - old_path);
+		*new_dir = xstrdup("");
+		return;
 	}
+
+	/*
+	 * We've found the first non-matching character in the directory
+	 * paths.  That means the current characters we were looking at
+	 * were part of the first non-matching subdir name going back from
+	 * the end of the strings.  Get the whole name by advancing both
+	 * end_of_old and end_of_new to the NEXT '/' character.  That will
+	 * represent the entire directory rename.
+	 *
+	 * The reason for the increment is cases like
+	 *    a/b/star/foo/whatever.c -> a/b/tar/foo/random.c
+	 * After dropping the basename and going back to the first
+	 * non-matching character, we're now comparing:
+	 *    a/b/s          and         a/b/
+	 * and we want to be comparing:
+	 *    a/b/star/      and         a/b/tar/
+	 * but without the pre-increment, the one on the right would stay
+	 * a/b/.
+	 */
+	end_of_old = strchr(++end_of_old, '/');
+	end_of_new = strchr(++end_of_new, '/');
+
+	/* Copy the old and new directories into *old_dir and *new_dir. */
+	*old_dir = xstrndup(old_path, end_of_old - old_path);
+	*new_dir = xstrndup(new_path, end_of_new - new_path);
 }
 
 static void remove_hashmap_entries(struct hashmap *dir_renames,
@@ -2001,7 +2022,7 @@ static void remove_hashmap_entries(struct hashmap *dir_renames,
 
 	for (i = 0; i < items_to_remove->nr; i++) {
 		entry = items_to_remove->items[i].util;
-		hashmap_remove(dir_renames, entry, NULL);
+		hashmap_remove(dir_renames, &entry->ent, NULL);
 	}
 	string_list_clear(items_to_remove, 0);
 }
@@ -2124,8 +2145,8 @@ static void handle_directory_level_conflicts(struct merge_options *opt,
 	struct string_list remove_from_head = STRING_LIST_INIT_NODUP;
 	struct string_list remove_from_merge = STRING_LIST_INIT_NODUP;
 
-	hashmap_iter_init(dir_re_head, &iter);
-	while ((head_ent = hashmap_iter_next(&iter))) {
+	hashmap_for_each_entry(dir_re_head, &iter, head_ent,
+				ent /* member name */) {
 		merge_ent = dir_rename_find_entry(dir_re_merge, head_ent->dir);
 		if (merge_ent &&
 		    !head_ent->non_unique_new_dir &&
@@ -2149,8 +2170,8 @@ static void handle_directory_level_conflicts(struct merge_options *opt,
 	remove_hashmap_entries(dir_re_head, &remove_from_head);
 	remove_hashmap_entries(dir_re_merge, &remove_from_merge);
 
-	hashmap_iter_init(dir_re_merge, &iter);
-	while ((merge_ent = hashmap_iter_next(&iter))) {
+	hashmap_for_each_entry(dir_re_merge, &iter, merge_ent,
+				ent /* member name */) {
 		head_ent = dir_rename_find_entry(dir_re_head, merge_ent->dir);
 		if (tree_has_path(opt->repo, merge, merge_ent->dir)) {
 			/* 2. This wasn't a directory rename after all */
@@ -2229,7 +2250,7 @@ static struct hashmap *get_directory_renames(struct diff_queue_struct *pairs)
 		if (!entry) {
 			entry = xmalloc(sizeof(*entry));
 			dir_rename_entry_init(entry, old_dir);
-			hashmap_put(dir_renames, entry);
+			hashmap_put(dir_renames, &entry->ent);
 		} else {
 			free(old_dir);
 		}
@@ -2254,8 +2275,8 @@ static struct hashmap *get_directory_renames(struct diff_queue_struct *pairs)
 	 * we set non_unique_new_dir.  Once we've determined the winner (or
 	 * that there is no winner), we no longer need possible_new_dirs.
 	 */
-	hashmap_iter_init(dir_renames, &iter);
-	while ((entry = hashmap_iter_next(&iter))) {
+	hashmap_for_each_entry(dir_renames, &iter, entry,
+				ent /* member name */) {
 		int max = 0;
 		int bad_max = 0;
 		char *best = NULL;
@@ -2358,8 +2379,9 @@ static void compute_collisions(struct hashmap *collisions,
 		if (!collision_ent) {
 			collision_ent = xcalloc(1,
 						sizeof(struct collision_entry));
-			hashmap_entry_init(collision_ent, strhash(new_path));
-			hashmap_put(collisions, collision_ent);
+			hashmap_entry_init(&collision_ent->ent,
+						strhash(new_path));
+			hashmap_put(collisions, &collision_ent->ent);
 			collision_ent->target_file = new_path;
 		} else {
 			free(new_path);
@@ -2612,12 +2634,12 @@ static struct string_list *get_renames(struct merge_options *opt,
 							     entries);
 	}
 
-	hashmap_iter_init(&collisions, &iter);
-	while ((e = hashmap_iter_next(&iter))) {
+	hashmap_for_each_entry(&collisions, &iter, e,
+				ent /* member name */) {
 		free(e->target_file);
 		string_list_clear(&e->source_files, 0);
 	}
-	hashmap_free(&collisions, 1);
+	hashmap_free_entries(&collisions, struct collision_entry, ent);
 	return renames;
 }
 
@@ -2756,15 +2778,15 @@ static int process_renames(struct merge_options *opt,
 			dst_other.mode = ren1->dst_entry->stages[other_stage].mode;
 			try_merge = 0;
 
-			if (oid_eq(&src_other.oid, &null_oid) &&
+			if (oideq(&src_other.oid, &null_oid) &&
 			    ren1->dir_rename_original_type == 'A') {
 				setup_rename_conflict_info(RENAME_VIA_DIR,
 							   opt, ren1, NULL);
-			} else if (oid_eq(&src_other.oid, &null_oid)) {
+			} else if (oideq(&src_other.oid, &null_oid)) {
 				setup_rename_conflict_info(RENAME_DELETE,
 							   opt, ren1, NULL);
 			} else if ((dst_other.mode == ren1->pair->two->mode) &&
-				   oid_eq(&dst_other.oid, &ren1->pair->two->oid)) {
+				   oideq(&dst_other.oid, &ren1->pair->two->oid)) {
 				/*
 				 * Added file on the other side identical to
 				 * the file being renamed: clean merge.
@@ -2779,7 +2801,7 @@ static int process_renames(struct merge_options *opt,
 						      1, /* update_cache */
 						      0  /* update_wd    */))
 					clean_merge = -1;
-			} else if (!oid_eq(&dst_other.oid, &null_oid)) {
+			} else if (!oideq(&dst_other.oid, &null_oid)) {
 				/*
 				 * Probably not a clean merge, but it's
 				 * premature to set clean_merge to 0 here,
@@ -2830,13 +2852,13 @@ static void initial_cleanup_rename(struct diff_queue_struct *pairs,
 	struct hashmap_iter iter;
 	struct dir_rename_entry *e;
 
-	hashmap_iter_init(dir_renames, &iter);
-	while ((e = hashmap_iter_next(&iter))) {
+	hashmap_for_each_entry(dir_renames, &iter, e,
+				ent /* member name */) {
 		free(e->dir);
 		strbuf_release(&e->new_dir);
 		/* possible_new_dirs already cleared in get_directory_renames */
 	}
-	hashmap_free(dir_renames, 1);
+	hashmap_free_entries(dir_renames, struct dir_rename_entry, ent);
 	free(dir_renames);
 
 	free(pairs->queue);
@@ -2863,8 +2885,9 @@ static int detect_and_process_renames(struct merge_options *opt,
 	head_pairs = get_diffpairs(opt, common, head);
 	merge_pairs = get_diffpairs(opt, common, merge);
 
-	if ((opt->detect_directory_renames == 2) ||
-	    (opt->detect_directory_renames == 1 && !opt->call_depth)) {
+	if ((opt->detect_directory_renames == MERGE_DIRECTORY_RENAMES_TRUE) ||
+	    (opt->detect_directory_renames == MERGE_DIRECTORY_RENAMES_CONFLICT &&
+	     !opt->priv->call_depth)) {
 		dir_re_head = get_directory_renames(head_pairs);
 		dir_re_merge = get_directory_renames(merge_pairs);
 
@@ -2956,7 +2979,7 @@ static int blob_unchanged(struct merge_options *opt,
 
 	if (a->mode != o->mode)
 		return 0;
-	if (oid_eq(&o->oid, &a->oid))
+	if (oideq(&o->oid, &a->oid))
 		return 1;
 	if (!renormalize)
 		return 0;
@@ -3021,13 +3044,13 @@ static int handle_content_merge(struct merge_file_info *mfi,
 		reason = _("add/add");
 
 	assert(o->path && a->path && b->path);
-	if (ci && dir_in_way(opt->repo->index, path, !opt->call_depth,
+	if (ci && dir_in_way(opt->repo->index, path, !opt->priv->call_depth,
 			     S_ISGITLINK(ci->ren1->pair->two->mode)))
 		df_conflict_remains = 1;
 
 	if (merge_mode_and_contents(opt, o, a, b, path,
 				    opt->branch1, opt->branch2,
-				    opt->call_depth * 2, mfi))
+				    opt->priv->call_depth * 2, mfi))
 		return -1;
 
 	/*
@@ -3043,7 +3066,7 @@ static int handle_content_merge(struct merge_file_info *mfi,
 
 		output(opt, 3, _("Skipped %s (merged same as existing)"), path);
 		if (add_cacheinfo(opt, &mfi->blob, path,
-				  0, (!opt->call_depth && !is_dirty), 0))
+				  0, (!opt->priv->call_depth && !is_dirty), 0))
 			return -1;
 		/*
 		 * However, add_cacheinfo() will delete the old cache entry
@@ -3051,8 +3074,8 @@ static int handle_content_merge(struct merge_file_info *mfi,
 		 * flag to avoid making the file appear as if it were
 		 * deleted by the user.
 		 */
-		pos = index_name_pos(&opt->orig_index, path, strlen(path));
-		ce = opt->orig_index.cache[pos];
+		pos = index_name_pos(&opt->priv->orig_index, path, strlen(path));
+		ce = opt->priv->orig_index.cache[pos];
 		if (ce_skip_worktree(ce)) {
 			pos = index_name_pos(opt->repo->index, path, strlen(path));
 			ce = opt->repo->index->cache[pos];
@@ -3073,7 +3096,7 @@ static int handle_content_merge(struct merge_file_info *mfi,
 
 	if (df_conflict_remains || is_dirty) {
 		char *new_path;
-		if (opt->call_depth) {
+		if (opt->priv->call_depth) {
 			remove_file_from_index(opt->repo->index, path);
 		} else {
 			if (!mfi->clean) {
@@ -3122,7 +3145,8 @@ static int handle_rename_normal(struct merge_options *opt,
 	clean = handle_content_merge(&mfi, opt, path, was_dirty(opt, path),
 				     o, a, b, ci);
 
-	if (clean && opt->detect_directory_renames == 1 &&
+	if (clean &&
+	    opt->detect_directory_renames == MERGE_DIRECTORY_RENAMES_CONFLICT &&
 	    ren->dir_rename_original_dest) {
 		if (update_stages(opt, path,
 				  NULL,
@@ -3167,12 +3191,12 @@ static int warn_about_dir_renamed_entries(struct merge_options *opt,
 		return clean;
 
 	/* Sanity checks */
-	assert(opt->detect_directory_renames > 0);
+	assert(opt->detect_directory_renames > MERGE_DIRECTORY_RENAMES_NONE);
 	assert(ren->dir_rename_original_type == 'A' ||
 	       ren->dir_rename_original_type == 'R');
 
 	/* Check whether to treat directory renames as a conflict */
-	clean = (opt->detect_directory_renames == 2);
+	clean = (opt->detect_directory_renames == MERGE_DIRECTORY_RENAMES_TRUE);
 
 	is_add = (ren->dir_rename_original_type == 'A');
 	if (ren->dir_rename_original_type == 'A' && clean) {
@@ -3331,7 +3355,7 @@ static int process_entry(struct merge_options *opt,
 			conf = _("directory/file");
 		}
 		if (dir_in_way(opt->repo->index, path,
-			       !opt->call_depth && !S_ISGITLINK(a->mode),
+			       !opt->priv->call_depth && !S_ISGITLINK(a->mode),
 			       0)) {
 			char *new_path = unique_path(opt, path, add_branch);
 			clean_merge = 0;
@@ -3340,7 +3364,7 @@ static int process_entry(struct merge_options *opt,
 			       conf, path, other_branch, path, new_path);
 			if (update_file(opt, 0, contents, new_path))
 				clean_merge = -1;
-			else if (opt->call_depth)
+			else if (opt->priv->call_depth)
 				remove_file_from_index(opt->repo->index, path);
 			free(new_path);
 		} else {
@@ -3380,37 +3404,32 @@ static int process_entry(struct merge_options *opt,
 	return clean_merge;
 }
 
-int merge_trees(struct merge_options *opt,
-		struct tree *head,
-		struct tree *merge,
-		struct tree *common,
-		struct tree **result)
+static int merge_trees_internal(struct merge_options *opt,
+				struct tree *head,
+				struct tree *merge,
+				struct tree *merge_base,
+				struct tree **result)
 {
 	struct index_state *istate = opt->repo->index;
 	int code, clean;
-	struct strbuf sb = STRBUF_INIT;
-
-	if (!opt->call_depth && repo_index_has_changes(opt->repo, head, &sb)) {
-		err(opt, _("Your local changes to the following files would be overwritten by merge:\n  %s"),
-		    sb.buf);
-		return -1;
-	}
 
 	if (opt->subtree_shift) {
-		merge = shift_tree_object(opt->repo, head, merge, opt->subtree_shift);
-		common = shift_tree_object(opt->repo, head, common, opt->subtree_shift);
+		merge = shift_tree_object(opt->repo, head, merge,
+					  opt->subtree_shift);
+		merge_base = shift_tree_object(opt->repo, head, merge_base,
+					       opt->subtree_shift);
 	}
 
-	if (oid_eq(&common->object.oid, &merge->object.oid)) {
+	if (oideq(&merge_base->object.oid, &merge->object.oid)) {
 		output(opt, 0, _("Already up to date!"));
 		*result = head;
 		return 1;
 	}
 
-	code = unpack_trees_start(opt, common, head, merge);
+	code = unpack_trees_start(opt, merge_base, head, merge);
 
 	if (code != 0) {
-		if (show(opt, 4) || opt->call_depth)
+		if (show(opt, 4) || opt->priv->call_depth)
 			err(opt, _("merging of trees %s and %s failed"),
 			    oid_to_hex(&head->object.oid),
 			    oid_to_hex(&merge->object.oid));
@@ -3429,12 +3448,13 @@ int merge_trees(struct merge_options *opt,
 		 * opposed to decaring a local hashmap is for convenience
 		 * so that we don't have to pass it to around.
 		 */
-		hashmap_init(&opt->current_file_dir_set, path_hashmap_cmp, NULL, 512);
+		hashmap_init(&opt->priv->current_file_dir_set, path_hashmap_cmp,
+			     NULL, 512);
 		get_files_dirs(opt, head);
 		get_files_dirs(opt, merge);
 
 		entries = get_unmerged(opt->repo->index);
-		clean = detect_and_process_renames(opt, common, head, merge,
+		clean = detect_and_process_renames(opt, merge_base, head, merge,
 						   entries, &re_info);
 		record_df_conflict_files(opt, entries);
 		if (clean < 0)
@@ -3465,7 +3485,8 @@ int merge_trees(struct merge_options *opt,
 		string_list_clear(entries, 1);
 		free(entries);
 
-		hashmap_free(&opt->current_file_dir_set, 1);
+		hashmap_free_entries(&opt->priv->current_file_dir_set,
+					struct path_hashmap_entry, e);
 
 		if (clean < 0) {
 			unpack_trees_finish(opt);
@@ -3477,7 +3498,8 @@ int merge_trees(struct merge_options *opt,
 
 	unpack_trees_finish(opt);
 
-	if (opt->call_depth && !(*result = write_tree_from_memory(opt)))
+	if (opt->priv->call_depth &&
+	    !(*result = write_in_core_index_as_tree(opt->repo)))
 		return -1;
 
 	return clean;
@@ -3498,16 +3520,18 @@ static struct commit_list *reverse_commit_list(struct commit_list *list)
  * Merge the commits h1 and h2, return the resulting virtual
  * commit object and a flag indicating the cleanness of the merge.
  */
-int merge_recursive(struct merge_options *opt,
-		    struct commit *h1,
-		    struct commit *h2,
-		    struct commit_list *ca,
-		    struct commit **result)
+static int merge_recursive_internal(struct merge_options *opt,
+				    struct commit *h1,
+				    struct commit *h2,
+				    struct commit_list *merge_bases,
+				    struct commit **result)
 {
 	struct commit_list *iter;
-	struct commit *merged_common_ancestors;
-	struct tree *mrtree;
+	struct commit *merged_merge_bases;
+	struct tree *result_tree;
 	int clean;
+	const char *ancestor_name;
+	struct strbuf merge_base_abbrev = STRBUF_INIT;
 
 	if (show(opt, 4)) {
 		output(opt, 4, _("Merging:"));
@@ -3515,32 +3539,43 @@ int merge_recursive(struct merge_options *opt,
 		output_commit_title(opt, h2);
 	}
 
-	if (!ca) {
-		ca = get_merge_bases(h1, h2);
-		ca = reverse_commit_list(ca);
+	if (!merge_bases) {
+		merge_bases = get_merge_bases(h1, h2);
+		merge_bases = reverse_commit_list(merge_bases);
 	}
 
 	if (show(opt, 5)) {
-		unsigned cnt = commit_list_count(ca);
+		unsigned cnt = commit_list_count(merge_bases);
 
 		output(opt, 5, Q_("found %u common ancestor:",
 				"found %u common ancestors:", cnt), cnt);
-		for (iter = ca; iter; iter = iter->next)
+		for (iter = merge_bases; iter; iter = iter->next)
 			output_commit_title(opt, iter->item);
 	}
 
-	merged_common_ancestors = pop_commit(&ca);
-	if (merged_common_ancestors == NULL) {
+	merged_merge_bases = pop_commit(&merge_bases);
+	if (merged_merge_bases == NULL) {
 		/* if there is no common ancestor, use an empty tree */
 		struct tree *tree;
 
 		tree = lookup_tree(opt->repo, opt->repo->hash_algo->empty_tree);
-		merged_common_ancestors = make_virtual_commit(opt->repo, tree, "ancestor");
+		merged_merge_bases = make_virtual_commit(opt->repo, tree,
+							 "ancestor");
+		ancestor_name = "empty tree";
+	} else if (opt->ancestor && !opt->priv->call_depth) {
+		ancestor_name = opt->ancestor;
+	} else if (merge_bases) {
+		ancestor_name = "merged common ancestors";
+	} else {
+		strbuf_add_unique_abbrev(&merge_base_abbrev,
+					 &merged_merge_bases->object.oid,
+					 DEFAULT_ABBREV);
+		ancestor_name = merge_base_abbrev.buf;
 	}
 
-	for (iter = ca; iter; iter = iter->next) {
+	for (iter = merge_bases; iter; iter = iter->next) {
 		const char *saved_b1, *saved_b2;
-		opt->call_depth++;
+		opt->priv->call_depth++;
 		/*
 		 * When the merge fails, the result contains files
 		 * with conflict markers. The cleanness flag is
@@ -3554,45 +3589,134 @@ int merge_recursive(struct merge_options *opt,
 		saved_b2 = opt->branch2;
 		opt->branch1 = "Temporary merge branch 1";
 		opt->branch2 = "Temporary merge branch 2";
-		if (merge_recursive(opt, merged_common_ancestors, iter->item,
-				    NULL, &merged_common_ancestors) < 0)
+		if (merge_recursive_internal(opt, merged_merge_bases, iter->item,
+					     NULL, &merged_merge_bases) < 0)
 			return -1;
 		opt->branch1 = saved_b1;
 		opt->branch2 = saved_b2;
-		opt->call_depth--;
+		opt->priv->call_depth--;
 
-		if (!merged_common_ancestors)
+		if (!merged_merge_bases)
 			return err(opt, _("merge returned no commit"));
 	}
 
 	discard_index(opt->repo->index);
-	if (!opt->call_depth)
+	if (!opt->priv->call_depth)
 		repo_read_index(opt->repo);
 
-	opt->ancestor = "merged common ancestors";
-	clean = merge_trees(opt, get_commit_tree(h1), get_commit_tree(h2),
-			    get_commit_tree(merged_common_ancestors),
-			    &mrtree);
+	opt->ancestor = ancestor_name;
+	clean = merge_trees_internal(opt,
+				     repo_get_commit_tree(opt->repo, h1),
+				     repo_get_commit_tree(opt->repo, h2),
+				     repo_get_commit_tree(opt->repo,
+							  merged_merge_bases),
+				     &result_tree);
+	strbuf_release(&merge_base_abbrev);
+	opt->ancestor = NULL;  /* avoid accidental re-use of opt->ancestor */
 	if (clean < 0) {
 		flush_output(opt);
 		return clean;
 	}
 
-	if (opt->call_depth) {
-		*result = make_virtual_commit(opt->repo, mrtree, "merged tree");
+	if (opt->priv->call_depth) {
+		*result = make_virtual_commit(opt->repo, result_tree,
+					      "merged tree");
 		commit_list_insert(h1, &(*result)->parents);
 		commit_list_insert(h2, &(*result)->parents->next);
 	}
+	return clean;
+}
+
+static int merge_start(struct merge_options *opt, struct tree *head)
+{
+	struct strbuf sb = STRBUF_INIT;
+
+	/* Sanity checks on opt */
+	assert(opt->repo);
+
+	assert(opt->branch1 && opt->branch2);
+
+	assert(opt->detect_renames >= -1 &&
+	       opt->detect_renames <= DIFF_DETECT_COPY);
+	assert(opt->detect_directory_renames >= MERGE_DIRECTORY_RENAMES_NONE &&
+	       opt->detect_directory_renames <= MERGE_DIRECTORY_RENAMES_TRUE);
+	assert(opt->rename_limit >= -1);
+	assert(opt->rename_score >= 0 && opt->rename_score <= MAX_SCORE);
+	assert(opt->show_rename_progress >= 0 && opt->show_rename_progress <= 1);
+
+	assert(opt->xdl_opts >= 0);
+	assert(opt->recursive_variant >= MERGE_VARIANT_NORMAL &&
+	       opt->recursive_variant <= MERGE_VARIANT_THEIRS);
+
+	assert(opt->verbosity >= 0 && opt->verbosity <= 5);
+	assert(opt->buffer_output <= 2);
+	assert(opt->obuf.len == 0);
+
+	assert(opt->priv == NULL);
+
+	/* Sanity check on repo state; index must match head */
+	if (repo_index_has_changes(opt->repo, head, &sb)) {
+		err(opt, _("Your local changes to the following files would be overwritten by merge:\n  %s"),
+		    sb.buf);
+		strbuf_release(&sb);
+		return -1;
+	}
+
+	opt->priv = xcalloc(1, sizeof(*opt->priv));
+	string_list_init(&opt->priv->df_conflict_file_set, 1);
+	return 0;
+}
+
+static void merge_finalize(struct merge_options *opt)
+{
 	flush_output(opt);
-	if (!opt->call_depth && opt->buffer_output < 2)
+	if (!opt->priv->call_depth && opt->buffer_output < 2)
 		strbuf_release(&opt->obuf);
 	if (show(opt, 2))
 		diff_warn_rename_limit("merge.renamelimit",
-				       opt->needed_rename_limit, 0);
+				       opt->priv->needed_rename_limit, 0);
+	FREE_AND_NULL(opt->priv);
+}
+
+int merge_trees(struct merge_options *opt,
+		struct tree *head,
+		struct tree *merge,
+		struct tree *merge_base)
+{
+	int clean;
+	struct tree *ignored;
+
+	assert(opt->ancestor != NULL);
+
+	if (merge_start(opt, head))
+		return -1;
+	clean = merge_trees_internal(opt, head, merge, merge_base, &ignored);
+	merge_finalize(opt);
+
 	return clean;
 }
 
-static struct commit *get_ref(struct repository *repo, const struct object_id *oid,
+int merge_recursive(struct merge_options *opt,
+		    struct commit *h1,
+		    struct commit *h2,
+		    struct commit_list *merge_bases,
+		    struct commit **result)
+{
+	int clean;
+
+	assert(opt->ancestor == NULL ||
+	       !strcmp(opt->ancestor, "constructed merge base"));
+
+	if (merge_start(opt, repo_get_commit_tree(opt->repo, h1)))
+		return -1;
+	clean = merge_recursive_internal(opt, h1, h2, merge_bases, result);
+	merge_finalize(opt);
+
+	return clean;
+}
+
+static struct commit *get_ref(struct repository *repo,
+			      const struct object_id *oid,
 			      const char *name)
 {
 	struct object *object;
@@ -3613,8 +3737,8 @@ static struct commit *get_ref(struct repository *repo, const struct object_id *o
 int merge_recursive_generic(struct merge_options *opt,
 			    const struct object_id *head,
 			    const struct object_id *merge,
-			    int num_base_list,
-			    const struct object_id **base_list,
+			    int num_merge_bases,
+			    const struct object_id **merge_bases,
 			    struct commit **result)
 {
 	int clean;
@@ -3623,15 +3747,18 @@ int merge_recursive_generic(struct merge_options *opt,
 	struct commit *next_commit = get_ref(opt->repo, merge, opt->branch2);
 	struct commit_list *ca = NULL;
 
-	if (base_list) {
+	if (merge_bases) {
 		int i;
-		for (i = 0; i < num_base_list; ++i) {
+		for (i = 0; i < num_merge_bases; ++i) {
 			struct commit *base;
-			if (!(base = get_ref(opt->repo, base_list[i], oid_to_hex(base_list[i]))))
+			if (!(base = get_ref(opt->repo, merge_bases[i],
+					     oid_to_hex(merge_bases[i]))))
 				return err(opt, _("Could not parse object '%s'"),
-					   oid_to_hex(base_list[i]));
+					   oid_to_hex(merge_bases[i]));
 			commit_list_insert(base, &ca);
 		}
+		if (num_merge_bases == 1)
+			opt->ancestor = "constructed merge base";
 	}
 
 	repo_hold_locked_index(opt->repo, &lock, LOCK_DIE_ON_ERROR);
@@ -3653,22 +3780,25 @@ static void merge_recursive_config(struct merge_options *opt)
 {
 	char *value = NULL;
 	git_config_get_int("merge.verbosity", &opt->verbosity);
-	git_config_get_int("diff.renamelimit", &opt->diff_rename_limit);
-	git_config_get_int("merge.renamelimit", &opt->merge_rename_limit);
+	git_config_get_int("diff.renamelimit", &opt->rename_limit);
+	git_config_get_int("merge.renamelimit", &opt->rename_limit);
 	if (!git_config_get_string("diff.renames", &value)) {
-		opt->diff_detect_rename = git_config_rename("diff.renames", value);
+		opt->detect_renames = git_config_rename("diff.renames", value);
 		free(value);
 	}
 	if (!git_config_get_string("merge.renames", &value)) {
-		opt->merge_detect_rename = git_config_rename("merge.renames", value);
+		opt->detect_renames = git_config_rename("merge.renames", value);
 		free(value);
 	}
 	if (!git_config_get_string("merge.directoryrenames", &value)) {
 		int boolval = git_parse_maybe_bool(value);
 		if (0 <= boolval) {
-			opt->detect_directory_renames = boolval ? 2 : 0;
+			opt->detect_directory_renames = boolval ?
+				MERGE_DIRECTORY_RENAMES_TRUE :
+				MERGE_DIRECTORY_RENAMES_NONE;
 		} else if (!strcasecmp(value, "conflict")) {
-			opt->detect_directory_renames = 1;
+			opt->detect_directory_renames =
+				MERGE_DIRECTORY_RENAMES_CONFLICT;
 		} /* avoid erroring on values from future versions of git */
 		free(value);
 	}
@@ -3680,23 +3810,25 @@ void init_merge_options(struct merge_options *opt,
 {
 	const char *merge_verbosity;
 	memset(opt, 0, sizeof(struct merge_options));
+
 	opt->repo = repo;
+
+	opt->detect_renames = -1;
+	opt->detect_directory_renames = MERGE_DIRECTORY_RENAMES_CONFLICT;
+	opt->rename_limit = -1;
+
 	opt->verbosity = 2;
 	opt->buffer_output = 1;
-	opt->diff_rename_limit = -1;
-	opt->merge_rename_limit = -1;
+	strbuf_init(&opt->obuf, 0);
+
 	opt->renormalize = 0;
-	opt->diff_detect_rename = -1;
-	opt->merge_detect_rename = -1;
-	opt->detect_directory_renames = 1;
+
 	merge_recursive_config(opt);
 	merge_verbosity = getenv("GIT_MERGE_VERBOSITY");
 	if (merge_verbosity)
 		opt->verbosity = strtol(merge_verbosity, NULL, 10);
 	if (opt->verbosity >= 5)
 		opt->buffer_output = 0;
-	strbuf_init(&opt->obuf, 0);
-	string_list_init(&opt->df_conflict_file_set, 1);
 }
 
 int parse_merge_opt(struct merge_options *opt, const char *s)
@@ -3706,9 +3838,9 @@ int parse_merge_opt(struct merge_options *opt, const char *s)
 	if (!s || !*s)
 		return -1;
 	if (!strcmp(s, "ours"))
-		opt->recursive_variant = MERGE_RECURSIVE_OURS;
+		opt->recursive_variant = MERGE_VARIANT_OURS;
 	else if (!strcmp(s, "theirs"))
-		opt->recursive_variant = MERGE_RECURSIVE_THEIRS;
+		opt->recursive_variant = MERGE_VARIANT_THEIRS;
 	else if (!strcmp(s, "subtree"))
 		opt->subtree_shift = "";
 	else if (skip_prefix(s, "subtree=", &arg))
@@ -3739,16 +3871,16 @@ int parse_merge_opt(struct merge_options *opt, const char *s)
 	else if (!strcmp(s, "no-renormalize"))
 		opt->renormalize = 0;
 	else if (!strcmp(s, "no-renames"))
-		opt->merge_detect_rename = 0;
+		opt->detect_renames = 0;
 	else if (!strcmp(s, "find-renames")) {
-		opt->merge_detect_rename = 1;
+		opt->detect_renames = 1;
 		opt->rename_score = 0;
 	}
 	else if (skip_prefix(s, "find-renames=", &arg) ||
 		 skip_prefix(s, "rename-threshold=", &arg)) {
 		if ((opt->rename_score = parse_rename_score(&arg)) == -1 || *arg != 0)
 			return -1;
-		opt->merge_detect_rename = 1;
+		opt->detect_renames = 1;
 	}
 	/*
 	 * Please update $__git_merge_strategy_options in