1 files changed, 233 insertions, 184 deletions

diff --git a/builtin/merge.c b/builtin/merge.c
index a8a843b..6f4fec8 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -6,37 +6,42 @@
  * Based on git-merge.sh by Junio C Hamano.
  */
 
-#define USE_THE_INDEX_COMPATIBILITY_MACROS
-#include "cache.h"
+#define USE_THE_INDEX_VARIABLE
+#include "builtin.h"
+#include "abspath.h"
+#include "advice.h"
 #include "config.h"
+#include "editor.h"
+#include "environment.h"
+#include "gettext.h"
+#include "hex.h"
+#include "object-name.h"
 #include "parse-options.h"
-#include "builtin.h"
 #include "lockfile.h"
 #include "run-command.h"
+#include "hook.h"
 #include "diff.h"
 #include "diff-merges.h"
 #include "refs.h"
 #include "refspec.h"
 #include "commit.h"
 #include "diffcore.h"
+#include "path.h"
 #include "revision.h"
 #include "unpack-trees.h"
 #include "cache-tree.h"
 #include "dir.h"
-#include "utf8.h"
-#include "log-tree.h"
 #include "color.h"
 #include "rerere.h"
 #include "help.h"
+#include "merge.h"
 #include "merge-recursive.h"
 #include "merge-ort-wrappers.h"
 #include "resolve-undo.h"
 #include "remote.h"
 #include "fmt-merge-msg.h"
-#include "gpg-interface.h"
 #include "sequencer.h"
 #include "string-list.h"
-#include "packfile.h"
 #include "tag.h"
 #include "alias.h"
 #include "branch.h"
@@ -70,8 +75,7 @@ static int overwrite_ignore = 1;
 static struct strbuf merge_msg = STRBUF_INIT;
 static struct strategy **use_strategies;
 static size_t use_strategies_nr, use_strategies_alloc;
-static const char **xopts;
-static size_t xopts_nr, xopts_alloc;
+static struct strvec xopts = STRVEC_INIT;
 static const char *branch;
 static char *branch_mergeoptions;
 static int verbosity;
@@ -86,11 +90,12 @@ static int signoff;
 static const char *sign_commit;
 static int autostash;
 static int no_verify;
+static char *into_name;
 
 static struct strategy all_strategy[] = {
-	{ "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
+	{ "recursive",  NO_TRIVIAL },
 	{ "octopus",    DEFAULT_OCTOPUS },
-	{ "ort",        NO_TRIVIAL },
+	{ "ort",        DEFAULT_TWOHEAD | NO_TRIVIAL },
 	{ "resolve",    0 },
 	{ "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
 	{ "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
@@ -186,9 +191,8 @@ static struct strategy *get_strategy(const char *name)
 		for (i = 0; i < main_cmds.cnt; i++) {
 			int j, found = 0;
 			struct cmdname *ent = main_cmds.names[i];
-			for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
-				if (!strncmp(ent->name, all_strategy[j].name, ent->len)
-						&& !all_strategy[j].name[ent->len])
+			for (j = 0; !found && j < ARRAY_SIZE(all_strategy); j++)
+				if (!xstrncmpz(all_strategy[j].name, ent->name, ent->len))
 					found = 1;
 			if (!found)
 				add_cmdname(&not_strategies, ent->name, ent->len);
@@ -222,7 +226,7 @@ static void append_strategy(struct strategy *s)
 	use_strategies[use_strategies_nr++] = s;
 }
 
-static int option_parse_strategy(const struct option *opt,
+static int option_parse_strategy(const struct option *opt UNUSED,
 				 const char *name, int unset)
 {
 	if (unset)
@@ -232,29 +236,9 @@ static int option_parse_strategy(const struct option *opt,
 	return 0;
 }
 
-static int option_parse_x(const struct option *opt,
-			  const char *arg, int unset)
-{
-	if (unset)
-		return 0;
-
-	ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
-	xopts[xopts_nr++] = xstrdup(arg);
-	return 0;
-}
-
-static int option_parse_n(const struct option *opt,
-			  const char *arg, int unset)
-{
-	BUG_ON_OPT_ARG(arg);
-	show_diffstat = unset;
-	return 0;
-}
-
 static struct option builtin_merge_options[] = {
-	OPT_CALLBACK_F('n', NULL, NULL, NULL,
-		N_("do not show a diffstat at the end of the merge"),
-		PARSE_OPT_NOARG, option_parse_n),
+	OPT_SET_INT('n', NULL, &show_diffstat,
+		N_("do not show a diffstat at the end of the merge"), 0),
 	OPT_BOOL(0, "stat", &show_diffstat,
 		N_("show a diffstat at the end of the merge")),
 	OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
@@ -275,16 +259,18 @@ static struct option builtin_merge_options[] = {
 	OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
 	OPT_BOOL(0, "verify-signatures", &verify_signatures,
 		N_("verify that the named commit has a valid GPG signature")),
-	OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
+	OPT_CALLBACK('s', "strategy", NULL, N_("strategy"),
 		N_("merge strategy to use"), option_parse_strategy),
-	OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
-		N_("option for selected merge strategy"), option_parse_x),
+	OPT_STRVEC('X', "strategy-option", &xopts, N_("option=value"),
+		N_("option for selected merge strategy")),
 	OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
 		N_("merge commit message (for a non-fast-forward merge)"),
 		option_parse_message),
 	{ OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
 		N_("read message from file"), PARSE_OPT_NONEG,
 		NULL, 0, option_read_message },
+	OPT_STRING(0, "into-name", &into_name, N_("name"),
+		   N_("use <name> instead of the real target")),
 	OPT__VERBOSITY(&verbosity),
 	OPT_BOOL(0, "abort", &abort_current_merge,
 		N_("abort the current in-progress merge")),
@@ -309,10 +295,17 @@ static int save_state(struct object_id *stash)
 	int len;
 	struct child_process cp = CHILD_PROCESS_INIT;
 	struct strbuf buffer = STRBUF_INIT;
-	const char *argv[] = {"stash", "create", NULL};
+	struct lock_file lock_file = LOCK_INIT;
+	int fd;
 	int rc = -1;
 
-	cp.argv = argv;
+	fd = repo_hold_locked_index(the_repository, &lock_file, 0);
+	refresh_index(&the_index, REFRESH_QUIET, NULL, NULL, NULL);
+	if (0 <= fd)
+		repo_update_index_if_able(the_repository, &lock_file);
+	rollback_lock_file(&lock_file);
+
+	strvec_pushl(&cp.args, "stash", "create", NULL);
 	cp.out = -1;
 	cp.git_cmd = 1;
 
@@ -326,7 +319,7 @@ static int save_state(struct object_id *stash)
 	else if (!len)		/* no changes */
 		goto out;
 	strbuf_setlen(&buffer, buffer.len-1);
-	if (get_oid(buffer.buf, stash))
+	if (repo_get_oid(the_repository, buffer.buf, stash))
 		die(_("not a valid object: %s"), buffer.buf);
 	rc = 0;
 out:
@@ -334,62 +327,54 @@ out:
 	return rc;
 }
 
-static void read_empty(const struct object_id *oid, int verbose)
+static void read_empty(const struct object_id *oid)
 {
-	int i = 0;
-	const char *args[7];
-
-	args[i++] = "read-tree";
-	if (verbose)
-		args[i++] = "-v";
-	args[i++] = "-m";
-	args[i++] = "-u";
-	args[i++] = empty_tree_oid_hex();
-	args[i++] = oid_to_hex(oid);
-	args[i] = NULL;
+	struct child_process cmd = CHILD_PROCESS_INIT;
 
-	if (run_command_v_opt(args, RUN_GIT_CMD))
+	strvec_pushl(&cmd.args, "read-tree", "-m", "-u", empty_tree_oid_hex(),
+		     oid_to_hex(oid), NULL);
+	cmd.git_cmd = 1;
+
+	if (run_command(&cmd))
 		die(_("read-tree failed"));
 }
 
-static void reset_hard(const struct object_id *oid, int verbose)
+static void reset_hard(const struct object_id *oid)
 {
-	int i = 0;
-	const char *args[6];
-
-	args[i++] = "read-tree";
-	if (verbose)
-		args[i++] = "-v";
-	args[i++] = "--reset";
-	args[i++] = "-u";
-	args[i++] = oid_to_hex(oid);
-	args[i] = NULL;
+	struct child_process cmd = CHILD_PROCESS_INIT;
 
-	if (run_command_v_opt(args, RUN_GIT_CMD))
+	strvec_pushl(&cmd.args, "read-tree", "-v", "--reset", "-u",
+		     oid_to_hex(oid), NULL);
+	cmd.git_cmd = 1;
+
+	if (run_command(&cmd))
 		die(_("read-tree failed"));
 }
 
 static void restore_state(const struct object_id *head,
 			  const struct object_id *stash)
 {
-	struct strbuf sb = STRBUF_INIT;
-	const char *args[] = { "stash", "apply", NULL, NULL };
+	struct child_process cmd = CHILD_PROCESS_INIT;
 
-	if (is_null_oid(stash))
-		return;
+	reset_hard(head);
 
-	reset_hard(head, 1);
+	if (is_null_oid(stash))
+		goto refresh_cache;
 
-	args[2] = oid_to_hex(stash);
+	strvec_pushl(&cmd.args, "stash", "apply", "--index", "--quiet", NULL);
+	strvec_push(&cmd.args, oid_to_hex(stash));
 
 	/*
 	 * It is OK to ignore error here, for example when there was
 	 * nothing to restore.
 	 */
-	run_command_v_opt(args, RUN_GIT_CMD);
+	cmd.git_cmd = 1;
+	run_command(&cmd);
 
-	strbuf_release(&sb);
-	refresh_cache(REFRESH_QUIET);
+refresh_cache:
+	discard_index(&the_index);
+	if (repo_read_index(the_repository) < 0)
+		die(_("could not read index"));
 }
 
 /* This is called when no merge was necessary. */
@@ -440,6 +425,7 @@ static void squash_message(struct commit *commit, struct commit_list *remotehead
 	}
 	write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
 	strbuf_release(&out);
+	release_revisions(&rev);
 }
 
 static void finish(struct commit *head_commit,
@@ -469,15 +455,13 @@ static void finish(struct commit *head_commit,
 			 * We ignore errors in 'gc --auto', since the
 			 * user should see them.
 			 */
-			close_object_store(the_repository->objects);
 			run_auto_maintenance(verbosity < 0);
 		}
 	}
 	if (new_head && show_diffstat) {
 		struct diff_options opts;
 		repo_diff_setup(the_repository, &opts);
-		opts.stat_width = -1; /* use full terminal width */
-		opts.stat_graph_width = -1; /* respect statGraphWidth config */
+		init_diffstat_widths(&opts);
 		opts.output_format |=
 			DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 		opts.detect_rename = DIFF_DETECT_RENAME;
@@ -488,9 +472,10 @@ static void finish(struct commit *head_commit,
 	}
 
 	/* Run a post-merge hook */
-	run_hook_le(NULL, "post-merge", squash ? "1" : "0", NULL);
+	run_hooks_l("post-merge", squash ? "1" : "0", NULL);
 
-	apply_autostash(git_path_merge_autostash(the_repository));
+	if (new_head)
+		apply_autostash_ref(the_repository, "MERGE_AUTOSTASH");
 	strbuf_release(&reflog_message);
 }
 
@@ -499,11 +484,10 @@ static void merge_name(const char *remote, struct strbuf *msg)
 {
 	struct commit *remote_head;
 	struct object_id branch_head;
-	struct strbuf buf = STRBUF_INIT;
 	struct strbuf bname = STRBUF_INIT;
 	struct merge_remote_desc *desc;
 	const char *ptr;
-	char *found_ref;
+	char *found_ref = NULL;
 	int len, early;
 
 	strbuf_branchname(&bname, remote, 0);
@@ -514,7 +498,8 @@ static void merge_name(const char *remote, struct strbuf *msg)
 	if (!remote_head)
 		die(_("'%s' does not point to a commit"), remote);
 
-	if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref, 0) > 0) {
+	if (repo_dwim_ref(the_repository, remote, strlen(remote), &branch_head,
+			  &found_ref, 0) > 0) {
 		if (starts_with(found_ref, "refs/heads/")) {
 			strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
 				    oid_to_hex(&branch_head), remote);
@@ -586,7 +571,7 @@ static void merge_name(const char *remote, struct strbuf *msg)
 	strbuf_addf(msg, "%s\t\tcommit '%s'\n",
 		oid_to_hex(&remote_head->object.oid), remote);
 cleanup:
-	strbuf_release(&buf);
+	free(found_ref);
 	strbuf_release(&bname);
 }
 
@@ -610,7 +595,8 @@ static void parse_branch_merge_options(char *bmo)
 	free(argv);
 }
 
-static int git_merge_config(const char *k, const char *v, void *cb)
+static int git_merge_config(const char *k, const char *v,
+			    const struct config_context *ctx, void *cb)
 {
 	int status;
 	const char *str;
@@ -655,13 +641,10 @@ static int git_merge_config(const char *k, const char *v, void *cb)
 		return 0;
 	}
 
-	status = fmt_merge_msg_config(k, v, cb);
-	if (status)
-		return status;
-	status = git_gpg_config(k, v, NULL);
+	status = fmt_merge_msg_config(k, v, ctx, cb);
 	if (status)
 		return status;
-	return git_diff_ui_config(k, v, cb);
+	return git_diff_ui_config(k, v, ctx, cb);
 }
 
 static int read_tree_trivial(struct object_id *common, struct object_id *head,
@@ -680,6 +663,7 @@ static int read_tree_trivial(struct object_id *common, struct object_id *head,
 	opts.verbose_update = 1;
 	opts.trivial_merges_only = 1;
 	opts.merge = 1;
+	opts.preserve_ignored = 0; /* FIXME: !overwrite_ignore */
 	trees[nr_trees] = parse_tree_indirect(common);
 	if (!trees[nr_trees++])
 		return -1;
@@ -690,10 +674,11 @@ static int read_tree_trivial(struct object_id *common, struct object_id *head,
 	if (!trees[nr_trees++])
 		return -1;
 	opts.fn = threeway_merge;
-	cache_tree_free(&active_cache_tree);
+	cache_tree_free(&the_index.cache_tree);
 	for (i = 0; i < nr_trees; i++) {
 		parse_tree(trees[i]);
-		init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
+		init_tree_desc(t+i, &trees[i]->object.oid,
+			       trees[i]->buffer, trees[i]->size);
 	}
 	if (unpack_trees(nr_trees, t, &opts))
 		return -1;
@@ -702,7 +687,7 @@ static int read_tree_trivial(struct object_id *common, struct object_id *head,
 
 static void write_tree_trivial(struct object_id *oid)
 {
-	if (write_cache_as_tree(oid, 0, NULL))
+	if (write_index_as_tree(oid, &the_index, get_index_file(), 0, NULL))
 		die(_("git write-tree failed to write a tree"));
 }
 
@@ -712,7 +697,9 @@ static int try_merge_strategy(const char *strategy, struct commit_list *common,
 {
 	const char *head_arg = "HEAD";
 
-	if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
+	if (repo_refresh_and_write_index(the_repository, REFRESH_QUIET,
+					 SKIP_IF_UNCHANGED, 0, NULL, NULL,
+					 NULL) < 0)
 		return error(_("Unable to write index."));
 
 	if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree") ||
@@ -736,9 +723,9 @@ static int try_merge_strategy(const char *strategy, struct commit_list *common,
 		o.show_rename_progress =
 			show_progress == -1 ? isatty(2) : show_progress;
 
-		for (x = 0; x < xopts_nr; x++)
-			if (parse_merge_opt(&o, xopts[x]))
-				die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
+		for (x = 0; x < xopts.nr; x++)
+			if (parse_merge_opt(&o, xopts.v[x]))
+				die(_("unknown strategy option: -X%s"), xopts.v[x]);
 
 		o.branch1 = head_arg;
 		o.branch2 = merge_remote_util(remoteheads->item)->name;
@@ -746,28 +733,31 @@ static int try_merge_strategy(const char *strategy, struct commit_list *common,
 		for (j = common; j; j = j->next)
 			commit_list_insert(j->item, &reversed);
 
-		hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
+		repo_hold_locked_index(the_repository, &lock,
+				       LOCK_DIE_ON_ERROR);
 		if (!strcmp(strategy, "ort"))
 			clean = merge_ort_recursive(&o, head, remoteheads->item,
 						    reversed, &result);
 		else
 			clean = merge_recursive(&o, head, remoteheads->item,
 						reversed, &result);
-		if (clean < 0)
-			exit(128);
+		if (clean < 0) {
+			rollback_lock_file(&lock);
+			return 2;
+		}
 		if (write_locked_index(&the_index, &lock,
 				       COMMIT_LOCK | SKIP_IF_UNCHANGED))
 			die(_("unable to write %s"), get_index_file());
 		return clean ? 0 : 1;
 	} else {
 		return try_merge_command(the_repository,
-					 strategy, xopts_nr, xopts,
+					 strategy, xopts.nr, xopts.v,
 					 common, head_arg, remoteheads);
 	}
 }
 
 static void count_diff_files(struct diff_queue_struct *q,
-			     struct diff_options *opt, void *data)
+			     struct diff_options *opt UNUSED, void *data)
 {
 	int *count = data;
 
@@ -778,8 +768,8 @@ static int count_unmerged_entries(void)
 {
 	int i, ret = 0;
 
-	for (i = 0; i < active_nr; i++)
-		if (ce_stage(active_cache[i]))
+	for (i = 0; i < the_index.cache_nr; i++)
+		if (ce_stage(the_index.cache[i]))
 			ret++;
 
 	return ret;
@@ -832,7 +822,7 @@ static const char scissors_editor_comment[] =
 N_("An empty message aborts the commit.\n");
 
 static const char no_scissors_editor_comment[] =
-N_("Lines starting with '%c' will be ignored, and an empty message aborts\n"
+N_("Lines starting with '%s' will be ignored, and an empty message aborts\n"
    "the commit.\n");
 
 static void write_merge_heads(struct commit_list *);
@@ -841,16 +831,21 @@ static void prepare_to_commit(struct commit_list *remoteheads)
 	struct strbuf msg = STRBUF_INIT;
 	const char *index_file = get_index_file();
 
-	if (!no_verify && run_commit_hook(0 < option_edit, index_file, "pre-merge-commit", NULL))
-		abort_commit(remoteheads, NULL);
-	/*
-	 * Re-read the index as pre-merge-commit hook could have updated it,
-	 * and write it out as a tree.  We must do this before we invoke
-	 * the editor and after we invoke run_status above.
-	 */
-	if (find_hook("pre-merge-commit"))
-		discard_cache();
-	read_cache_from(index_file);
+	if (!no_verify) {
+		int invoked_hook;
+
+		if (run_commit_hook(0 < option_edit, index_file, &invoked_hook,
+				    "pre-merge-commit", NULL))
+			abort_commit(remoteheads, NULL);
+		/*
+		 * Re-read the index as pre-merge-commit hook could have updated it,
+		 * and write it out as a tree.  We must do this before we invoke
+		 * the editor and after we invoke run_status above.
+		 */
+		if (invoked_hook)
+			discard_index(&the_index);
+	}
+	read_index_from(&the_index, index_file, get_git_dir());
 	strbuf_addbuf(&msg, &merge_msg);
 	if (squash)
 		BUG("the control must not reach here under --squash");
@@ -858,18 +853,23 @@ static void prepare_to_commit(struct commit_list *remoteheads)
 		strbuf_addch(&msg, '\n');
 		if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS) {
 			wt_status_append_cut_line(&msg);
-			strbuf_commented_addf(&msg, "\n");
+			strbuf_commented_addf(&msg, comment_line_str, "\n");
 		}
-		strbuf_commented_addf(&msg, _(merge_editor_comment));
-		strbuf_commented_addf(&msg, _(cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS ?
-			scissors_editor_comment :
-			no_scissors_editor_comment), comment_line_char);
+		strbuf_commented_addf(&msg, comment_line_str,
+				      _(merge_editor_comment));
+		if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS)
+			strbuf_commented_addf(&msg, comment_line_str,
+					      _(scissors_editor_comment));
+		else
+			strbuf_commented_addf(&msg, comment_line_str,
+				_(no_scissors_editor_comment), comment_line_str);
 	}
 	if (signoff)
-		append_signoff(&msg, ignore_non_trailer(msg.buf, msg.len), 0);
+		append_signoff(&msg, ignored_log_message_bytes(msg.buf, msg.len), 0);
 	write_merge_heads(remoteheads);
 	write_file_buf(git_path_merge_msg(the_repository), msg.buf, msg.len);
-	if (run_commit_hook(0 < option_edit, get_index_file(), "prepare-commit-msg",
+	if (run_commit_hook(0 < option_edit, get_index_file(), NULL,
+			    "prepare-commit-msg",
 			    git_path_merge_msg(the_repository), "merge", NULL))
 		abort_commit(remoteheads, NULL);
 	if (0 < option_edit) {
@@ -878,7 +878,7 @@ static void prepare_to_commit(struct commit_list *remoteheads)
 	}
 
 	if (!no_verify && run_commit_hook(0 < option_edit, get_index_file(),
-					  "commit-msg",
+					  NULL, "commit-msg",
 					  git_path_merge_msg(the_repository), NULL))
 		abort_commit(remoteheads, NULL);
 
@@ -896,7 +896,9 @@ static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 	struct object_id result_tree, result_commit;
 	struct commit_list *parents, **pptr = &parents;
 
-	if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
+	if (repo_refresh_and_write_index(the_repository, REFRESH_QUIET,
+					 SKIP_IF_UNCHANGED, 0, NULL, NULL,
+					 NULL) < 0)
 		return error(_("Unable to write index."));
 
 	write_tree_trivial(&result_tree);
@@ -986,6 +988,7 @@ static int evaluate_result(void)
 	 */
 	cnt += count_unmerged_entries();
 
+	release_revisions(&rev);
 	return cnt;
 }
 
@@ -1118,6 +1121,7 @@ static void prepare_merge_message(struct strbuf *merge_names, struct strbuf *mer
 	opts.add_title = !have_message;
 	opts.shortlog_len = shortlog_len;
 	opts.credit_people = (0 < option_edit);
+	opts.into_name = into_name;
 
 	fmt_merge_msg(merge_names, merge_msg, &opts);
 	if (merge_msg->len)
@@ -1135,9 +1139,7 @@ static void handle_fetch_head(struct commit_list **remotes, struct strbuf *merge
 		merge_names = &fetch_head_file;
 
 	filename = git_path_fetch_head(the_repository);
-	fd = open(filename, O_RDONLY);
-	if (fd < 0)
-		die_errno(_("could not open '%s' for reading"), filename);
+	fd = xopen(filename, O_RDONLY);
 
 	if (strbuf_read(merge_names, fd, 0) < 0)
 		die_errno(_("could not read '%s'"), filename);
@@ -1268,13 +1270,16 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	int best_cnt = -1, merge_was_ok = 0, automerge_was_ok = 0;
 	struct commit_list *common = NULL;
 	const char *best_strategy = NULL, *wt_strategy = NULL;
-	struct commit_list *remoteheads, *p;
+	struct commit_list *remoteheads = NULL, *p;
 	void *branch_to_free;
 	int orig_argc = argc;
 
 	if (argc == 2 && !strcmp(argv[1], "-h"))
 		usage_with_options(builtin_merge_usage, builtin_merge_options);
 
+	prepare_repo_settings(the_repository);
+	the_repository->settings.command_requires_full_index = 0;
+
 	/*
 	 * Check if we are _not_ on a detached HEAD, i.e. if there is a
 	 * current branch.
@@ -1310,7 +1315,8 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	if (abort_current_merge) {
 		int nargc = 2;
 		const char *nargv[] = {"reset", "--merge", NULL};
-		struct strbuf stash_oid = STRBUF_INIT;
+		char stash_oid_hex[GIT_MAX_HEXSZ + 1];
+		struct object_id stash_oid = {0};
 
 		if (orig_argc != 2)
 			usage_msg_opt(_("--abort expects no arguments"),
@@ -1319,17 +1325,17 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		if (!file_exists(git_path_merge_head(the_repository)))
 			die(_("There is no merge to abort (MERGE_HEAD missing)."));
 
-		if (read_oneliner(&stash_oid, git_path_merge_autostash(the_repository),
-		    READ_ONELINER_SKIP_IF_EMPTY))
-			unlink(git_path_merge_autostash(the_repository));
+		if (!read_ref("MERGE_AUTOSTASH", &stash_oid))
+			delete_ref("", "MERGE_AUTOSTASH", &stash_oid, REF_NO_DEREF);
 
 		/* Invoke 'git reset --merge' */
 		ret = cmd_reset(nargc, nargv, prefix);
 
-		if (stash_oid.len)
-			apply_autostash_oid(stash_oid.buf);
+		if (!is_null_oid(&stash_oid)) {
+			oid_to_hex_r(stash_oid_hex, &stash_oid);
+			apply_autostash_oid(stash_oid_hex);
+		}
 
-		strbuf_release(&stash_oid);
 		goto done;
 	}
 
@@ -1359,7 +1365,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		goto done;
 	}
 
-	if (read_cache_unmerged())
+	if (repo_read_index_unmerged(the_repository))
 		die_resolve_conflict("merge");
 
 	if (file_exists(git_path_merge_head(the_repository))) {
@@ -1367,20 +1373,20 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		 * There is no unmerged entry, don't advise 'git
 		 * add/rm <file>', just 'git commit'.
 		 */
-		if (advice_resolve_conflict)
+		if (advice_enabled(ADVICE_RESOLVE_CONFLICT))
 			die(_("You have not concluded your merge (MERGE_HEAD exists).\n"
 				  "Please, commit your changes before you merge."));
 		else
 			die(_("You have not concluded your merge (MERGE_HEAD exists)."));
 	}
 	if (ref_exists("CHERRY_PICK_HEAD")) {
-		if (advice_resolve_conflict)
+		if (advice_enabled(ADVICE_RESOLVE_CONFLICT))
 			die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists).\n"
 			    "Please, commit your changes before you merge."));
 		else
 			die(_("You have not concluded your cherry-pick (CHERRY_PICK_HEAD exists)."));
 	}
-	resolve_undo_clear();
+	resolve_undo_clear_index(&the_index);
 
 	if (option_edit < 0)
 		option_edit = default_edit_option();
@@ -1392,9 +1398,9 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 
 	if (squash) {
 		if (fast_forward == FF_NO)
-			die(_("You cannot combine --squash with --no-ff."));
+			die(_("options '%s' and '%s' cannot be used together"), "--squash", "--no-ff.");
 		if (option_commit > 0)
-			die(_("You cannot combine --squash with --commit."));
+			die(_("options '%s' and '%s' cannot be used together"), "--squash", "--commit.");
 		/*
 		 * squash can now silently disable option_commit - this is not
 		 * a problem as it is only overriding the default, not a user
@@ -1443,7 +1449,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 					       check_trust_level);
 
 		remote_head_oid = &remoteheads->item->object.oid;
-		read_empty(remote_head_oid, 0);
+		read_empty(remote_head_oid);
 		update_ref("initial pull", "HEAD", remote_head_oid, NULL, 0,
 			   UPDATE_REFS_DIE_ON_ERR);
 		goto done;
@@ -1484,6 +1490,12 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 			fast_forward = FF_NO;
 	}
 
+	if (!use_strategies && !pull_twohead &&
+	    remoteheads && !remoteheads->next) {
+		char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
+		if (default_strategy)
+			append_strategy(get_strategy(default_strategy));
+	}
 	if (!use_strategies) {
 		if (!remoteheads)
 			; /* already up-to-date */
@@ -1502,12 +1514,20 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 
 	if (!remoteheads)
 		; /* already up-to-date */
-	else if (!remoteheads->next)
-		common = get_merge_bases(head_commit, remoteheads->item);
-	else {
+	else if (!remoteheads->next) {
+		if (repo_get_merge_bases(the_repository, head_commit,
+					 remoteheads->item, &common) < 0) {
+			ret = 2;
+			goto done;
+		}
+	} else {
 		struct commit_list *list = remoteheads;
 		commit_list_insert(head_commit, &list);
-		common = get_octopus_merge_bases(list);
+		if (get_octopus_merge_bases(list, &common) < 0) {
+			free(list);
+			ret = 2;
+			goto done;
+		}
 		free(list);
 	}
 
@@ -1532,20 +1552,18 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 			!common->next &&
 			oideq(&common->item->object.oid, &head_commit->object.oid)) {
 		/* Again the most common case of merging one remote. */
-		struct strbuf msg = STRBUF_INIT;
+		const char *msg = have_message ?
+			"Fast-forward (no commit created; -m option ignored)" :
+			"Fast-forward";
 		struct commit *commit;
 
 		if (verbosity >= 0) {
 			printf(_("Updating %s..%s\n"),
-			       find_unique_abbrev(&head_commit->object.oid,
-						  DEFAULT_ABBREV),
-			       find_unique_abbrev(&remoteheads->item->object.oid,
-						  DEFAULT_ABBREV));
+			       repo_find_unique_abbrev(the_repository, &head_commit->object.oid,
+						       DEFAULT_ABBREV),
+			       repo_find_unique_abbrev(the_repository, &remoteheads->item->object.oid,
+						       DEFAULT_ABBREV));
 		}
-		strbuf_addstr(&msg, "Fast-forward");
-		if (have_message)
-			strbuf_addstr(&msg,
-				" (no commit created; -m option ignored)");
 		commit = remoteheads->item;
 		if (!commit) {
 			ret = 1;
@@ -1553,18 +1571,17 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		}
 
 		if (autostash)
-			create_autostash(the_repository,
-					 git_path_merge_autostash(the_repository),
-					 "merge");
+			create_autostash_ref(the_repository, "MERGE_AUTOSTASH");
 		if (checkout_fast_forward(the_repository,
 					  &head_commit->object.oid,
 					  &commit->object.oid,
 					  overwrite_ignore)) {
+			apply_autostash_ref(the_repository, "MERGE_AUTOSTASH");
 			ret = 1;
 			goto done;
 		}
 
-		finish(head_commit, remoteheads, &commit->object.oid, msg.buf);
+		finish(head_commit, remoteheads, &commit->object.oid, msg);
 		remove_merge_branch_state(the_repository);
 		goto done;
 	} else if (!remoteheads->next && common->next)
@@ -1578,8 +1595,25 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		 * We are not doing octopus, not fast-forward, and have
 		 * only one common.
 		 */
-		refresh_cache(REFRESH_QUIET);
+		refresh_index(&the_index, REFRESH_QUIET, NULL, NULL, NULL);
 		if (allow_trivial && fast_forward != FF_ONLY) {
+			/*
+			 * Must first ensure that index matches HEAD before
+			 * attempting a trivial merge.
+			 */
+			struct tree *head_tree = repo_get_commit_tree(the_repository,
+								      head_commit);
+			struct strbuf sb = STRBUF_INIT;
+
+			if (repo_index_has_changes(the_repository, head_tree,
+						   &sb)) {
+				error(_("Your local changes to the following files would be overwritten by merge:\n  %s"),
+				      sb.buf);
+				strbuf_release(&sb);
+				ret = 2;
+				goto done;
+			}
+
 			/* See if it is really trivial. */
 			git_committer_info(IDENT_STRICT);
 			printf(_("Trying really trivial in-index merge...\n"));
@@ -1600,15 +1634,21 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		struct commit_list *j;
 
 		for (j = remoteheads; j; j = j->next) {
-			struct commit_list *common_one;
+			struct commit_list *common_one = NULL;
+			struct commit *common_item;
 
 			/*
 			 * Here we *have* to calculate the individual
 			 * merge_bases again, otherwise "git merge HEAD^
 			 * HEAD^^" would be missed.
 			 */
-			common_one = get_merge_bases(head_commit, j->item);
-			if (!oideq(&common_one->item->object.oid, &j->item->object.oid)) {
+			if (repo_get_merge_bases(the_repository, head_commit,
+						 j->item, &common_one) < 0)
+				exit(128);
+
+			common_item = common_one->item;
+			free_commit_list(common_one);
+			if (!oideq(&common_item->object.oid, &j->item->object.oid)) {
 				up_to_date = 0;
 				break;
 			}
@@ -1620,12 +1660,10 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	}
 
 	if (fast_forward == FF_ONLY)
-		die(_("Not possible to fast-forward, aborting."));
+		die_ff_impossible();
 
 	if (autostash)
-		create_autostash(the_repository,
-				 git_path_merge_autostash(the_repository),
-				 "merge");
+		create_autostash_ref(the_repository, "MERGE_AUTOSTASH");
 
 	/* We are going to make a new commit. */
 	git_committer_info(IDENT_STRICT);
@@ -1637,15 +1675,15 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	 * tree in the index -- this means that the index must be in
 	 * sync with the head commit.  The strategies are responsible
 	 * to ensure this.
+	 *
+	 * Stash away the local changes so that we can try more than one
+	 * and/or recover from merge strategies bailing while leaving the
+	 * index and working tree polluted.
 	 */
-	if (use_strategies_nr == 1 ||
-	    /*
-	     * Stash away the local changes so that we can try more than one.
-	     */
-	    save_state(&stash))
+	if (save_state(&stash))
 		oidclr(&stash);
 
-	for (i = 0; !merge_was_ok && i < use_strategies_nr; i++) {
+	for (i = 0; i < use_strategies_nr; i++) {
 		int ret, cnt;
 		if (i) {
 			printf(_("Rewinding the tree to pristine...\n"));
@@ -1660,7 +1698,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		 */
 		wt_strategy = use_strategies[i]->name;
 
-		ret = try_merge_strategy(use_strategies[i]->name,
+		ret = try_merge_strategy(wt_strategy,
 					 common, remoteheads,
 					 head_commit);
 		/*
@@ -1670,16 +1708,17 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		 */
 		if (ret < 2) {
 			if (!ret) {
-				if (option_commit) {
-					/* Automerge succeeded. */
-					automerge_was_ok = 1;
-					break;
-				}
+				/*
+				 * This strategy worked; no point in trying
+				 * another.
+				 */
 				merge_was_ok = 1;
+				best_strategy = wt_strategy;
+				break;
 			}
 			cnt = (use_strategies_nr > 1) ? evaluate_result() : 0;
 			if (best_cnt <= 0 || cnt <= best_cnt) {
-				best_strategy = use_strategies[i]->name;
+				best_strategy = wt_strategy;
 				best_cnt = cnt;
 			}
 		}
@@ -1689,7 +1728,8 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	 * If we have a resulting tree, that means the strategy module
 	 * auto resolved the merge cleanly.
 	 */
-	if (automerge_was_ok) {
+	if (merge_was_ok && option_commit) {
+		automerge_was_ok = 1;
 		ret = finish_automerge(head_commit, head_subsumed,
 				       common, remoteheads,
 				       &result_tree, wt_strategy);
@@ -1708,6 +1748,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		else
 			fprintf(stderr, _("Merge with strategy %s failed.\n"),
 				use_strategies[0]->name);
+		apply_autostash_ref(the_repository, "MERGE_AUTOSTASH");
 		ret = 2;
 		goto done;
 	} else if (best_strategy == wt_strategy)
@@ -1715,7 +1756,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	else {
 		printf(_("Rewinding the tree to pristine...\n"));
 		restore_state(&head_commit->object.oid, &stash);
-		printf(_("Using the %s to prepare resolving by hand.\n"),
+		printf(_("Using the %s strategy to prepare resolving by hand.\n"),
 			best_strategy);
 		try_merge_strategy(best_strategy, common, remoteheads,
 				   head_commit);
@@ -1733,8 +1774,16 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 			"stopped before committing as requested\n"));
 	else
 		ret = suggest_conflicts();
+	if (autostash)
+		printf(_("When finished, apply stashed changes with `git stash pop`\n"));
 
 done:
+	if (!automerge_was_ok) {
+		free_commit_list(common);
+		free_commit_list(remoteheads);
+	}
+	strbuf_release(&buf);
 	free(branch_to_free);
+	discard_index(&the_index);
 	return ret;
 }