merge(3p/git): Merge git subtree at v2.29.2 r/1890

This also bumps the stable nixpkgs to 20.09 as of 2020-11-21, because
there is some breakage in the git build related to the netrc
credentials helper which someone has taken care of in nixpkgs.

The stable channel is not used for anything other than git, so this
should be fine.

Change-Id: I3575a19dab09e1e9556cf8231d717de9890484fb

1 files changed, 560 insertions, 412 deletions

diff --git a/third_party/git/merge-recursive.c b/third_party/git/merge-recursive.c
index 6b812d67e3ec..d0214335a79d 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, NULL)) {
 				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 +1710,78 @@ 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))
+	if (opt->priv->call_depth)
+		remove_file_from_index(opt->repo->index, o->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 {
+		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;
+	}
 
+	if (!mfi.clean && mfi.blob.mode == a->mode &&
+	    oideq(&mfi.blob.oid, &a->oid)) {
 		/*
-		 * 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.
+		 * Getting here means we were attempting to merge a binary
+		 * blob.  Since we can't merge binaries, the merge algorithm
+		 * just takes one side.  But we don't want to copy the
+		 * contents of one side to both paths; we'd rather use the
+		 * original content at the given path for each path.
 		 */
-		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);
+		oidcpy(&mfi.blob.oid, &b->oid);
+		mfi.blob.mode = b->mode;
+	}
+	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 {
-		/*
-		 * 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;
-		}
-
-		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;
-		}
+		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 +1811,19 @@ 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 +1857,15 @@ 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 +1905,16 @@ 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 +1927,8 @@ 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 +1939,91 @@ 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 +2034,7 @@ 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 +2157,8 @@ 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 +2182,8 @@ 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 +2262,7 @@ 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 +2287,8 @@ 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 +2391,9 @@ 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 +2646,12 @@ 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 +2790,15 @@ 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 +2813,7 @@ 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 +2864,13 @@ 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 +2897,9 @@ 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 +2991,7 @@ 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 +3056,13 @@ 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 +3078,7 @@ 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 +3086,8 @@ 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 +3108,7 @@ 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 +3157,8 @@ 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 +3203,12 @@ 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 +3367,7 @@ 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 +3376,7 @@ 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 +3416,32 @@ 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 +3460,13 @@ 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 +3497,8 @@ 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 +3510,8 @@ 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;
@@ -3495,19 +3529,22 @@ 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.
+ * Merge the commits h1 and h2, returning a flag (int) indicating the
+ * cleanness of the merge.  Also, if opt->priv->call_depth, create a
+ * virtual commit and write its location to *result.
  */
-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 +3552,43 @@ 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 +3602,134 @@ 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 +3750,8 @@ 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 +3760,18 @@ 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);
@@ -3652,23 +3792,29 @@ int merge_recursive_generic(struct merge_options *opt,
 static void merge_recursive_config(struct merge_options *opt)
 {
 	char *value = NULL;
+	int renormalize = 0;
 	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);
+	git_config_get_bool("merge.renormalize", &renormalize);
+	opt->renormalize = renormalize;
 	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 +3826,25 @@ 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 +3854,9 @@ 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 +3887,16 @@ 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