1 files changed, 367 insertions, 205 deletions

diff --git a/builtin/merge.c b/builtin/merge.c
index 325891edb6..470fc57c5d 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -26,6 +26,8 @@
 #include "merge-recursive.h"
 #include "resolve-undo.h"
 #include "remote.h"
+#include "fmt-merge-msg.h"
+#include "gpg-interface.h"
 
 #define DEFAULT_TWOHEAD (1<<0)
 #define DEFAULT_OCTOPUS (1<<1)
@@ -44,13 +46,12 @@ static const char * const builtin_merge_usage[] = {
 	NULL
 };
 
-static int show_diffstat = 1, shortlog_len, squash;
+static int show_diffstat = 1, shortlog_len = -1, squash;
 static int option_commit = 1, allow_fast_forward = 1;
-static int fast_forward_only;
+static int fast_forward_only, option_edit = -1;
 static int allow_trivial = 1, have_message;
-static struct strbuf merge_msg;
-static struct commit_list *remoteheads;
-static unsigned char head[20], stash[20];
+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;
@@ -63,6 +64,7 @@ static int allow_rerere_auto;
 static int abort_current_merge;
 static int show_progress = -1;
 static int default_to_upstream;
+static const char *sign_commit;
 
 static struct strategy all_strategy[] = {
 	{ "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
@@ -190,6 +192,8 @@ static struct option builtin_merge_options[] = {
 		"create a single commit instead of doing a merge"),
 	OPT_BOOLEAN(0, "commit", &option_commit,
 		"perform a commit if the merge succeeds (default)"),
+	OPT_BOOL('e', "edit", &option_edit,
+		"edit message before committing"),
 	OPT_BOOLEAN(0, "ff", &allow_fast_forward,
 		"allow fast-forward (default)"),
 	OPT_BOOLEAN(0, "ff-only", &fast_forward_only,
@@ -206,6 +210,9 @@ static struct option builtin_merge_options[] = {
 	OPT_BOOLEAN(0, "abort", &abort_current_merge,
 		"abort the current in-progress merge"),
 	OPT_SET_INT(0, "progress", &show_progress, "force progress reporting", 1),
+	{ OPTION_STRING, 'S', "gpg-sign", &sign_commit, "key id",
+	  "GPG sign commit", PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
+	OPT_BOOLEAN(0, "overwrite-ignore", &overwrite_ignore, "update ignored files (default)"),
 	OPT_END()
 };
 
@@ -217,7 +224,7 @@ static void drop_save(void)
 	unlink(git_path("MERGE_MODE"));
 }
 
-static void save_state(void)
+static int save_state(unsigned char *stash)
 {
 	int len;
 	struct child_process cp;
@@ -236,11 +243,12 @@ static void save_state(void)
 
 	if (finish_command(&cp) || len < 0)
 		die(_("stash failed"));
-	else if (!len)
-		return;
+	else if (!len)		/* no changes */
+		return -1;
 	strbuf_setlen(&buffer, buffer.len-1);
 	if (get_sha1(buffer.buf, stash))
 		die(_("not a valid object: %s"), buffer.buf);
+	return 0;
 }
 
 static void read_empty(unsigned const char *sha1, int verbose)
@@ -278,7 +286,8 @@ static void reset_hard(unsigned const char *sha1, int verbose)
 		die(_("read-tree failed"));
 }
 
-static void restore_state(void)
+static void restore_state(const unsigned char *head,
+			  const unsigned char *stash)
 {
 	struct strbuf sb = STRBUF_INIT;
 	const char *args[] = { "stash", "apply", NULL, NULL };
@@ -308,25 +317,25 @@ static void finish_up_to_date(const char *msg)
 	drop_save();
 }
 
-static void squash_message(void)
+static void squash_message(struct commit *commit, struct commit_list *remoteheads)
 {
 	struct rev_info rev;
-	struct commit *commit;
 	struct strbuf out = STRBUF_INIT;
 	struct commit_list *j;
+	const char *filename;
 	int fd;
 	struct pretty_print_context ctx = {0};
 
 	printf(_("Squash commit -- not updating HEAD\n"));
-	fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
+	filename = git_path("SQUASH_MSG");
+	fd = open(filename, O_WRONLY | O_CREAT, 0666);
 	if (fd < 0)
-		die_errno(_("Could not write to '%s'"), git_path("SQUASH_MSG"));
+		die_errno(_("Could not write to '%s'"), filename);
 
 	init_revisions(&rev, NULL);
 	rev.ignore_merges = 1;
 	rev.commit_format = CMIT_FMT_MEDIUM;
 
-	commit = lookup_commit(head);
 	commit->object.flags |= UNINTERESTING;
 	add_pending_object(&rev, &commit->object, NULL);
 
@@ -355,9 +364,12 @@ static void squash_message(void)
 	strbuf_release(&out);
 }
 
-static void finish(const unsigned char *new_head, const char *msg)
+static void finish(struct commit *head_commit,
+		   struct commit_list *remoteheads,
+		   const unsigned char *new_head, const char *msg)
 {
 	struct strbuf reflog_message = STRBUF_INIT;
+	const unsigned char *head = head_commit->object.sha1;
 
 	if (!msg)
 		strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
@@ -368,7 +380,7 @@ static void finish(const unsigned char *new_head, const char *msg)
 			getenv("GIT_REFLOG_ACTION"), msg);
 	}
 	if (squash) {
-		squash_message();
+		squash_message(head_commit, remoteheads);
 	} else {
 		if (verbosity >= 0 && !merge_msg.len)
 			printf(_("No merge message -- not updating HEAD\n"));
@@ -387,11 +399,11 @@ static void finish(const unsigned char *new_head, const char *msg)
 	if (new_head && show_diffstat) {
 		struct diff_options opts;
 		diff_setup(&opts);
+		opts.stat_width = -1; /* use full terminal width */
+		opts.stat_graph_width = -1; /* respect statGraphWidth config */
 		opts.output_format |=
 			DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
 		opts.detect_rename = DIFF_DETECT_RENAME;
-		if (diff_use_color_default > 0)
-			DIFF_OPT_SET(&opts, COLOR_DIFF);
 		if (diff_setup_done(&opts) < 0)
 			die(_("diff_setup_done failed"));
 		diff_tree_sha1(head, new_head, "", &opts);
@@ -408,8 +420,8 @@ static void finish(const unsigned char *new_head, const char *msg)
 /* Get the name for the merge commit's message. */
 static void merge_name(const char *remote, struct strbuf *msg)
 {
-	struct object *remote_head;
-	unsigned char branch_head[20], buf_sha[20];
+	struct commit *remote_head;
+	unsigned char branch_head[20];
 	struct strbuf buf = STRBUF_INIT;
 	struct strbuf bname = STRBUF_INIT;
 	const char *ptr;
@@ -420,7 +432,7 @@ static void merge_name(const char *remote, struct strbuf *msg)
 	remote = bname.buf;
 
 	memset(branch_head, 0, sizeof(branch_head));
-	remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
+	remote_head = get_merge_parent(remote);
 	if (!remote_head)
 		die(_("'%s' does not point to a commit"), remote);
 
@@ -430,6 +442,11 @@ static void merge_name(const char *remote, struct strbuf *msg)
 				    sha1_to_hex(branch_head), remote);
 			goto cleanup;
 		}
+		if (!prefixcmp(found_ref, "refs/tags/")) {
+			strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
+				    sha1_to_hex(branch_head), remote);
+			goto cleanup;
+		}
 		if (!prefixcmp(found_ref, "refs/remotes/")) {
 			strbuf_addf(msg, "%s\t\tremote-tracking branch '%s' of .\n",
 				    sha1_to_hex(branch_head), remote);
@@ -468,10 +485,10 @@ static void merge_name(const char *remote, struct strbuf *msg)
 		strbuf_addstr(&truname, "refs/heads/");
 		strbuf_addstr(&truname, remote);
 		strbuf_setlen(&truname, truname.len - len);
-		if (resolve_ref(truname.buf, buf_sha, 1, NULL)) {
+		if (ref_exists(truname.buf)) {
 			strbuf_addf(msg,
 				    "%s\t\tbranch '%s'%s of .\n",
-				    sha1_to_hex(remote_head->sha1),
+				    sha1_to_hex(remote_head->object.sha1),
 				    truname.buf + 11,
 				    (early ? " (early part)" : ""));
 			strbuf_release(&truname);
@@ -481,14 +498,16 @@ static void merge_name(const char *remote, struct strbuf *msg)
 
 	if (!strcmp(remote, "FETCH_HEAD") &&
 			!access(git_path("FETCH_HEAD"), R_OK)) {
+		const char *filename;
 		FILE *fp;
 		struct strbuf line = STRBUF_INIT;
 		char *ptr;
 
-		fp = fopen(git_path("FETCH_HEAD"), "r");
+		filename = git_path("FETCH_HEAD");
+		fp = fopen(filename, "r");
 		if (!fp)
 			die_errno(_("could not open '%s' for reading"),
-				  git_path("FETCH_HEAD"));
+				  filename);
 		strbuf_getline(&line, fp, '\n');
 		fclose(fp);
 		ptr = strstr(line.buf, "\tnot-for-merge\t");
@@ -499,7 +518,7 @@ static void merge_name(const char *remote, struct strbuf *msg)
 		goto cleanup;
 	}
 	strbuf_addf(msg, "%s\t\tcommit '%s'\n",
-		sha1_to_hex(remote_head->sha1), remote);
+		sha1_to_hex(remote_head->object.sha1), remote);
 cleanup:
 	strbuf_release(&buf);
 	strbuf_release(&bname);
@@ -527,6 +546,8 @@ static void parse_branch_merge_options(char *bmo)
 
 static int git_merge_config(const char *k, const char *v, void *cb)
 {
+	int status;
+
 	if (branch && !prefixcmp(k, "branch.") &&
 		!prefixcmp(k + 7, branch) &&
 		!strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
@@ -543,15 +564,7 @@ static int git_merge_config(const char *k, const char *v, void *cb)
 		return git_config_string(&pull_octopus, k, v);
 	else if (!strcmp(k, "merge.renormalize"))
 		option_renormalize = git_config_bool(k, v);
-	else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary")) {
-		int is_bool;
-		shortlog_len = git_config_bool_or_int(k, v, &is_bool);
-		if (!is_bool && shortlog_len < 0)
-			return error(_("%s: negative length %s"), k, v);
-		if (is_bool && shortlog_len)
-			shortlog_len = DEFAULT_MERGE_LOG_LEN;
-		return 0;
-	} else if (!strcmp(k, "merge.ff")) {
+	else if (!strcmp(k, "merge.ff")) {
 		int boolval = git_config_maybe_bool(k, v);
 		if (0 <= boolval) {
 			allow_fast_forward = boolval;
@@ -564,6 +577,13 @@ static int git_merge_config(const char *k, const char *v, void *cb)
 		default_to_upstream = git_config_bool(k, v);
 		return 0;
 	}
+
+	status = fmt_merge_msg_config(k, v, cb);
+	if (status)
+		return status;
+	status = git_gpg_config(k, v, NULL);
+	if (status)
+		return status;
 	return git_diff_ui_config(k, v, cb);
 }
 
@@ -663,7 +683,8 @@ int try_merge_command(const char *strategy, size_t xopts_nr,
 }
 
 static int try_merge_strategy(const char *strategy, struct commit_list *common,
-			      const char *head_arg)
+			      struct commit_list *remoteheads,
+			      struct commit *head, const char *head_arg)
 {
 	int index_fd;
 	struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
@@ -703,13 +724,13 @@ static int try_merge_strategy(const char *strategy, struct commit_list *common,
 				die(_("Unknown option for merge-recursive: -X%s"), xopts[x]);
 
 		o.branch1 = head_arg;
-		o.branch2 = remoteheads->item->util;
+		o.branch2 = merge_remote_util(remoteheads->item)->name;
 
 		for (j = common; j; j = j->next)
 			commit_list_insert(j->item, &reversed);
 
 		index_fd = hold_locked_index(lock, 1);
-		clean = merge_recursive(&o, lookup_commit(head),
+		clean = merge_recursive(&o, head,
 				remoteheads->item, reversed, &result);
 		if (active_cache_changed &&
 				(write_cache(index_fd, active_cache, active_nr) ||
@@ -758,10 +779,12 @@ int checkout_fast_forward(const unsigned char *head, const unsigned char *remote
 	memset(&trees, 0, sizeof(trees));
 	memset(&opts, 0, sizeof(opts));
 	memset(&t, 0, sizeof(t));
-	memset(&dir, 0, sizeof(dir));
-	dir.flags |= DIR_SHOW_IGNORED;
-	dir.exclude_per_dir = ".gitignore";
-	opts.dir = &dir;
+	if (overwrite_ignore) {
+		memset(&dir, 0, sizeof(dir));
+		dir.flags |= DIR_SHOW_IGNORED;
+		setup_standard_excludes(&dir);
+		opts.dir = &dir;
+	}
 
 	opts.head_idx = 1;
 	opts.src_index = &the_index;
@@ -834,77 +857,110 @@ static void add_strategies(const char *string, unsigned attr)
 
 }
 
-static void write_merge_msg(void)
+static void write_merge_msg(struct strbuf *msg)
 {
-	int fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
+	const char *filename = git_path("MERGE_MSG");
+	int fd = open(filename, O_WRONLY | O_CREAT, 0666);
 	if (fd < 0)
 		die_errno(_("Could not open '%s' for writing"),
-			  git_path("MERGE_MSG"));
-	if (write_in_full(fd, merge_msg.buf, merge_msg.len) != merge_msg.len)
-		die_errno(_("Could not write to '%s'"), git_path("MERGE_MSG"));
+			  filename);
+	if (write_in_full(fd, msg->buf, msg->len) != msg->len)
+		die_errno(_("Could not write to '%s'"), filename);
 	close(fd);
 }
 
-static void read_merge_msg(void)
+static void read_merge_msg(struct strbuf *msg)
+{
+	const char *filename = git_path("MERGE_MSG");
+	strbuf_reset(msg);
+	if (strbuf_read_file(msg, filename, 0) < 0)
+		die_errno(_("Could not read from '%s'"), filename);
+}
+
+static void write_merge_state(struct commit_list *);
+static void abort_commit(struct commit_list *remoteheads, const char *err_msg)
 {
-	strbuf_reset(&merge_msg);
-	if (strbuf_read_file(&merge_msg, git_path("MERGE_MSG"), 0) < 0)
-		die_errno(_("Could not read from '%s'"), git_path("MERGE_MSG"));
+	if (err_msg)
+		error("%s", err_msg);
+	fprintf(stderr,
+		_("Not committing merge; use 'git commit' to complete the merge.\n"));
+	write_merge_state(remoteheads);
+	exit(1);
 }
 
-static void run_prepare_commit_msg(void)
+static const char merge_editor_comment[] =
+N_("Please enter a commit message to explain why this merge is necessary,\n"
+   "especially if it merges an updated upstream into a topic branch.\n"
+   "\n"
+   "Lines starting with '#' will be ignored, and an empty message aborts\n"
+   "the commit.\n");
+
+static void prepare_to_commit(struct commit_list *remoteheads)
 {
-	write_merge_msg();
+	struct strbuf msg = STRBUF_INIT;
+	const char *comment = _(merge_editor_comment);
+	strbuf_addbuf(&msg, &merge_msg);
+	strbuf_addch(&msg, '\n');
+	if (0 < option_edit)
+		strbuf_add_lines(&msg, "# ", comment, strlen(comment));
+	write_merge_msg(&msg);
 	run_hook(get_index_file(), "prepare-commit-msg",
 		 git_path("MERGE_MSG"), "merge", NULL, NULL);
-	read_merge_msg();
+	if (0 < option_edit) {
+		if (launch_editor(git_path("MERGE_MSG"), NULL, NULL))
+			abort_commit(remoteheads, NULL);
+	}
+	read_merge_msg(&msg);
+	stripspace(&msg, 0 < option_edit);
+	if (!msg.len)
+		abort_commit(remoteheads, _("Empty commit message."));
+	strbuf_release(&merge_msg);
+	strbuf_addbuf(&merge_msg, &msg);
+	strbuf_release(&msg);
 }
 
-static int merge_trivial(void)
+static int merge_trivial(struct commit *head, struct commit_list *remoteheads)
 {
 	unsigned char result_tree[20], result_commit[20];
 	struct commit_list *parent = xmalloc(sizeof(*parent));
 
 	write_tree_trivial(result_tree);
 	printf(_("Wonderful.\n"));
-	parent->item = lookup_commit(head);
+	parent->item = head;
 	parent->next = xmalloc(sizeof(*parent->next));
 	parent->next->item = remoteheads->item;
 	parent->next->next = NULL;
-	run_prepare_commit_msg();
-	commit_tree(merge_msg.buf, result_tree, parent, result_commit, NULL);
-	finish(result_commit, "In-index merge");
+	prepare_to_commit(remoteheads);
+	if (commit_tree(&merge_msg, result_tree, parent, result_commit, NULL,
+			sign_commit))
+		die(_("failed to write commit object"));
+	finish(head, remoteheads, result_commit, "In-index merge");
 	drop_save();
 	return 0;
 }
 
-static int finish_automerge(struct commit_list *common,
+static int finish_automerge(struct commit *head,
+			    int head_subsumed,
+			    struct commit_list *common,
+			    struct commit_list *remoteheads,
 			    unsigned char *result_tree,
 			    const char *wt_strategy)
 {
-	struct commit_list *parents = NULL, *j;
+	struct commit_list *parents = NULL;
 	struct strbuf buf = STRBUF_INIT;
 	unsigned char result_commit[20];
 
 	free_commit_list(common);
-	if (allow_fast_forward) {
-		parents = remoteheads;
-		commit_list_insert(lookup_commit(head), &parents);
-		parents = reduce_heads(parents);
-	} else {
-		struct commit_list **pptr = &parents;
-
-		pptr = &commit_list_insert(lookup_commit(head),
-				pptr)->next;
-		for (j = remoteheads; j; j = j->next)
-			pptr = &commit_list_insert(j->item, pptr)->next;
-	}
-	free_commit_list(remoteheads);
+	parents = remoteheads;
+	if (!head_subsumed || !allow_fast_forward)
+		commit_list_insert(head, &parents);
 	strbuf_addch(&merge_msg, '\n');
-	run_prepare_commit_msg();
-	commit_tree(merge_msg.buf, result_tree, parents, result_commit, NULL);
-	strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
-	finish(result_commit, buf.buf);
+	prepare_to_commit(remoteheads);
+	if (commit_tree(&merge_msg, result_tree, parents, result_commit,
+			NULL, sign_commit))
+		die(_("failed to write commit object"));
+	strbuf_addf(&buf, "Merge made by the '%s' strategy.", wt_strategy);
+	finish(head, remoteheads, result_commit, buf.buf);
 	strbuf_release(&buf);
 	drop_save();
 	return 0;
@@ -912,13 +968,14 @@ static int finish_automerge(struct commit_list *common,
 
 static int suggest_conflicts(int renormalizing)
 {
+	const char *filename;
 	FILE *fp;
 	int pos;
 
-	fp = fopen(git_path("MERGE_MSG"), "a");
+	filename = git_path("MERGE_MSG");
+	fp = fopen(filename, "a");
 	if (!fp)
-		die_errno(_("Could not open '%s' for writing"),
-			  git_path("MERGE_MSG"));
+		die_errno(_("Could not open '%s' for writing"), filename);
 	fprintf(fp, "\nConflicts:\n");
 	for (pos = 0; pos < active_nr; pos++) {
 		struct cache_entry *ce = active_cache[pos];
@@ -938,7 +995,8 @@ static int suggest_conflicts(int renormalizing)
 	return 1;
 }
 
-static struct commit *is_old_style_invocation(int argc, const char **argv)
+static struct commit *is_old_style_invocation(int argc, const char **argv,
+					      const unsigned char *head)
 {
 	struct commit *second_token = NULL;
 	if (argc > 2) {
@@ -1007,16 +1065,119 @@ static int setup_with_upstream(const char ***argv)
 	return i;
 }
 
+static void write_merge_state(struct commit_list *remoteheads)
+{
+	const char *filename;
+	int fd;
+	struct commit_list *j;
+	struct strbuf buf = STRBUF_INIT;
+
+	for (j = remoteheads; j; j = j->next) {
+		unsigned const char *sha1;
+		struct commit *c = j->item;
+		if (c->util && merge_remote_util(c)->obj) {
+			sha1 = merge_remote_util(c)->obj->sha1;
+		} else {
+			sha1 = c->object.sha1;
+		}
+		strbuf_addf(&buf, "%s\n", sha1_to_hex(sha1));
+	}
+	filename = git_path("MERGE_HEAD");
+	fd = open(filename, O_WRONLY | O_CREAT, 0666);
+	if (fd < 0)
+		die_errno(_("Could not open '%s' for writing"), filename);
+	if (write_in_full(fd, buf.buf, buf.len) != buf.len)
+		die_errno(_("Could not write to '%s'"), filename);
+	close(fd);
+	strbuf_addch(&merge_msg, '\n');
+	write_merge_msg(&merge_msg);
+
+	filename = git_path("MERGE_MODE");
+	fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0666);
+	if (fd < 0)
+		die_errno(_("Could not open '%s' for writing"), filename);
+	strbuf_reset(&buf);
+	if (!allow_fast_forward)
+		strbuf_addf(&buf, "no-ff");
+	if (write_in_full(fd, buf.buf, buf.len) != buf.len)
+		die_errno(_("Could not write to '%s'"), filename);
+	close(fd);
+}
+
+static int default_edit_option(void)
+{
+	static const char name[] = "GIT_MERGE_AUTOEDIT";
+	const char *e = getenv(name);
+	struct stat st_stdin, st_stdout;
+
+	if (have_message)
+		/* an explicit -m msg without --[no-]edit */
+		return 0;
+
+	if (e) {
+		int v = git_config_maybe_bool(name, e);
+		if (v < 0)
+			die("Bad value '%s' in environment '%s'", e, name);
+		return v;
+	}
+
+	/* Use editor if stdin and stdout are the same and is a tty */
+	return (!fstat(0, &st_stdin) &&
+		!fstat(1, &st_stdout) &&
+		isatty(0) && isatty(1) &&
+		st_stdin.st_dev == st_stdout.st_dev &&
+		st_stdin.st_ino == st_stdout.st_ino &&
+		st_stdin.st_mode == st_stdout.st_mode);
+}
+
+static struct commit_list *collect_parents(struct commit *head_commit,
+					   int *head_subsumed,
+					   int argc, const char **argv)
+{
+	int i;
+	struct commit_list *remoteheads = NULL, *parents, *next;
+	struct commit_list **remotes = &remoteheads;
+
+	if (head_commit)
+		remotes = &commit_list_insert(head_commit, remotes)->next;
+	for (i = 0; i < argc; i++) {
+		struct commit *commit = get_merge_parent(argv[i]);
+		if (!commit)
+			die(_("%s - not something we can merge"), argv[i]);
+		remotes = &commit_list_insert(commit, remotes)->next;
+	}
+	*remotes = NULL;
+
+	parents = reduce_heads(remoteheads);
+
+	*head_subsumed = 1; /* we will flip this to 0 when we find it */
+	for (remoteheads = NULL, remotes = &remoteheads;
+	     parents;
+	     parents = next) {
+		struct commit *commit = parents->item;
+		next = parents->next;
+		if (commit == head_commit)
+			*head_subsumed = 0;
+		else
+			remotes = &commit_list_insert(commit, remotes)->next;
+	}
+	return remoteheads;
+}
+
 int cmd_merge(int argc, const char **argv, const char *prefix)
 {
 	unsigned char result_tree[20];
+	unsigned char stash[20];
+	unsigned char head_sha1[20];
+	struct commit *head_commit;
 	struct strbuf buf = STRBUF_INIT;
 	const char *head_arg;
-	int flag, head_invalid = 0, i;
+	int flag, i, ret = 0, head_subsumed;
 	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 **remotes = &remoteheads;
+	struct commit_list *remoteheads, *p;
+	void *branch_to_free;
 
 	if (argc == 2 && !strcmp(argv[1], "-h"))
 		usage_with_options(builtin_merge_usage, builtin_merge_options);
@@ -1025,22 +1186,22 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	 * Check if we are _not_ on a detached HEAD, i.e. if there is a
 	 * current branch.
 	 */
-	branch = resolve_ref("HEAD", head, 0, &flag);
+	branch = branch_to_free = resolve_refdup("HEAD", head_sha1, 0, &flag);
 	if (branch && !prefixcmp(branch, "refs/heads/"))
 		branch += 11;
-	if (is_null_sha1(head))
-		head_invalid = 1;
+	if (!branch || is_null_sha1(head_sha1))
+		head_commit = NULL;
+	else
+		head_commit = lookup_commit_or_die(head_sha1, "HEAD");
 
 	git_config(git_merge_config, NULL);
 
-	/* for color.ui */
-	if (diff_use_color_default == -1)
-		diff_use_color_default = git_use_color_default;
-
 	if (branch_mergeoptions)
 		parse_branch_merge_options(branch_mergeoptions);
 	argc = parse_options(argc, argv, prefix, builtin_merge_options,
 			builtin_merge_usage, 0);
+	if (shortlog_len < 0)
+		shortlog_len = (merge_log_config > 0) ? merge_log_config : 0;
 
 	if (verbosity < 0 && show_progress == -1)
 		show_progress = 0;
@@ -1053,7 +1214,8 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 			die(_("There is no merge to abort (MERGE_HEAD missing)."));
 
 		/* Invoke 'git reset --merge' */
-		return cmd_reset(nargc, nargv, prefix);
+		ret = cmd_reset(nargc, nargv, prefix);
+		goto done;
 	}
 
 	if (read_cache_unmerged())
@@ -1092,9 +1254,12 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		die(_("You cannot combine --no-ff with --ff-only."));
 
 	if (!abort_current_merge) {
-		if (!argc && default_to_upstream)
-			argc = setup_with_upstream(&argv);
-		else if (argc == 1 && !strcmp(argv[0], "-"))
+		if (!argc) {
+			if (default_to_upstream)
+				argc = setup_with_upstream(&argv);
+			else
+				die(_("No commit specified and merge.defaultToUpstream not set."));
+		} else if (argc == 1 && !strcmp(argv[0], "-"))
 			argv[0] = "@{-1}";
 	}
 	if (!argc)
@@ -1110,13 +1275,15 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	 * additional safety measure to check for it.
 	 */
 
-	if (!have_message && is_old_style_invocation(argc, argv)) {
+	if (!have_message && head_commit &&
+	    is_old_style_invocation(argc, argv, head_commit->object.sha1)) {
 		strbuf_addstr(&merge_msg, argv[0]);
 		head_arg = argv[1];
 		argv += 2;
 		argc -= 2;
-	} else if (head_invalid) {
-		struct object *remote_head;
+		remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
+	} else if (!head_commit) {
+		struct commit *remote_head;
 		/*
 		 * If the merged head is a valid one there is no reason
 		 * to forbid "git merge" into a branch yet to be born.
@@ -1130,13 +1297,14 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		if (!allow_fast_forward)
 			die(_("Non-fast-forward commit does not make sense into "
 			    "an empty head"));
-		remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
+		remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
+		remote_head = remoteheads->item;
 		if (!remote_head)
 			die(_("%s - not something we can merge"), argv[0]);
-		read_empty(remote_head->sha1, 0);
-		update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
-				DIE_ON_ERR);
-		return 0;
+		read_empty(remote_head->object.sha1, 0);
+		update_ref("initial pull", "HEAD", remote_head->object.sha1,
+			   NULL, 0, DIE_ON_ERR);
+		goto done;
 	} else {
 		struct strbuf merge_names = STRBUF_INIT;
 
@@ -1144,52 +1312,56 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		head_arg = "HEAD";
 
 		/*
-		 * All the rest are the commits being merged;
-		 * prepare the standard merge summary message to
-		 * be appended to the given message.  If remote
-		 * is invalid we will die later in the common
-		 * codepath so we discard the error in this
-		 * loop.
+		 * All the rest are the commits being merged; prepare
+		 * the standard merge summary message to be appended
+		 * to the given message.
 		 */
-		for (i = 0; i < argc; i++)
-			merge_name(argv[i], &merge_names);
+		remoteheads = collect_parents(head_commit, &head_subsumed, argc, argv);
+		for (p = remoteheads; p; p = p->next)
+			merge_name(merge_remote_util(p->item)->name, &merge_names);
 
 		if (!have_message || shortlog_len) {
-			fmt_merge_msg(&merge_names, &merge_msg, !have_message,
-				      shortlog_len);
+			struct fmt_merge_msg_opts opts;
+			memset(&opts, 0, sizeof(opts));
+			opts.add_title = !have_message;
+			opts.shortlog_len = shortlog_len;
+
+			fmt_merge_msg(&merge_names, &merge_msg, &opts);
 			if (merge_msg.len)
 				strbuf_setlen(&merge_msg, merge_msg.len - 1);
 		}
 	}
 
-	if (head_invalid || !argc)
+	if (!head_commit || !argc)
 		usage_with_options(builtin_merge_usage,
 			builtin_merge_options);
 
 	strbuf_addstr(&buf, "merge");
-	for (i = 0; i < argc; i++)
-		strbuf_addf(&buf, " %s", argv[i]);
+	for (p = remoteheads; p; p = p->next)
+		strbuf_addf(&buf, " %s", merge_remote_util(p->item)->name);
 	setenv("GIT_REFLOG_ACTION", buf.buf, 0);
 	strbuf_reset(&buf);
 
-	for (i = 0; i < argc; i++) {
-		struct object *o;
-		struct commit *commit;
-
-		o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
-		if (!o)
-			die(_("%s - not something we can merge"), argv[i]);
-		commit = lookup_commit(o->sha1);
-		commit->util = (void *)argv[i];
-		remotes = &commit_list_insert(commit, remotes)->next;
-
-		strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
-		setenv(buf.buf, argv[i], 1);
+	for (p = remoteheads; p; p = p->next) {
+		struct commit *commit = p->item;
+		strbuf_addf(&buf, "GITHEAD_%s",
+			    sha1_to_hex(commit->object.sha1));
+		setenv(buf.buf, merge_remote_util(commit)->name, 1);
 		strbuf_reset(&buf);
+		if (!fast_forward_only &&
+		    merge_remote_util(commit) &&
+		    merge_remote_util(commit)->obj &&
+		    merge_remote_util(commit)->obj->type == OBJ_TAG)
+			allow_fast_forward = 0;
 	}
 
+	if (option_edit < 0)
+		option_edit = default_edit_option();
+
 	if (!use_strategies) {
-		if (!remoteheads->next)
+		if (!remoteheads)
+			; /* already up-to-date */
+		else if (!remoteheads->next)
 			add_strategies(pull_twohead, DEFAULT_TWOHEAD);
 		else
 			add_strategies(pull_octopus, DEFAULT_OCTOPUS);
@@ -1202,38 +1374,40 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 			allow_trivial = 0;
 	}
 
-	if (!remoteheads->next)
-		common = get_merge_bases(lookup_commit(head),
-				remoteheads->item, 1);
+	if (!remoteheads)
+		; /* already up-to-date */
+	else if (!remoteheads->next)
+		common = get_merge_bases(head_commit, remoteheads->item, 1);
 	else {
 		struct commit_list *list = remoteheads;
-		commit_list_insert(lookup_commit(head), &list);
+		commit_list_insert(head_commit, &list);
 		common = get_octopus_merge_bases(list);
 		free(list);
 	}
 
-	update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
-		DIE_ON_ERR);
+	update_ref("updating ORIG_HEAD", "ORIG_HEAD", head_commit->object.sha1,
+		   NULL, 0, DIE_ON_ERR);
 
-	if (!common)
+	if (remoteheads && !common)
 		; /* No common ancestors found. We need a real merge. */
-	else if (!remoteheads->next && !common->next &&
-			common->item == remoteheads->item) {
+	else if (!remoteheads ||
+		 (!remoteheads->next && !common->next &&
+		  common->item == remoteheads->item)) {
 		/*
 		 * If head can reach all the merge then we are up to date.
 		 * but first the most common case of merging one remote.
 		 */
 		finish_up_to_date("Already up-to-date.");
-		return 0;
+		goto done;
 	} else if (allow_fast_forward && !remoteheads->next &&
 			!common->next &&
-			!hashcmp(common->item->object.sha1, head)) {
+			!hashcmp(common->item->object.sha1, head_commit->object.sha1)) {
 		/* Again the most common case of merging one remote. */
 		struct strbuf msg = STRBUF_INIT;
-		struct object *o;
+		struct commit *commit;
 		char hex[41];
 
-		strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
+		strcpy(hex, find_unique_abbrev(head_commit->object.sha1, DEFAULT_ABBREV));
 
 		if (verbosity >= 0)
 			printf(_("Updating %s..%s\n"),
@@ -1244,17 +1418,21 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		if (have_message)
 			strbuf_addstr(&msg,
 				" (no commit created; -m option ignored)");
-		o = peel_to_type(sha1_to_hex(remoteheads->item->object.sha1),
-			0, NULL, OBJ_COMMIT);
-		if (!o)
-			return 1;
+		commit = remoteheads->item;
+		if (!commit) {
+			ret = 1;
+			goto done;
+		}
 
-		if (checkout_fast_forward(head, remoteheads->item->object.sha1))
-			return 1;
+		if (checkout_fast_forward(head_commit->object.sha1,
+					  commit->object.sha1)) {
+			ret = 1;
+			goto done;
+		}
 
-		finish(o->sha1, msg.buf);
+		finish(head_commit, remoteheads, commit->object.sha1, msg.buf);
 		drop_save();
-		return 0;
+		goto done;
 	} else if (!remoteheads->next && common->next)
 		;
 		/*
@@ -1272,8 +1450,11 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 			git_committer_info(IDENT_ERROR_ON_NO_NAME);
 			printf(_("Trying really trivial in-index merge...\n"));
 			if (!read_tree_trivial(common->item->object.sha1,
-					head, remoteheads->item->object.sha1))
-				return merge_trivial();
+					       head_commit->object.sha1,
+					       remoteheads->item->object.sha1)) {
+				ret = merge_trivial(head_commit, remoteheads);
+				goto done;
+			}
 			printf(_("Nope.\n"));
 		}
 	} else {
@@ -1292,8 +1473,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 			 * merge_bases again, otherwise "git merge HEAD^
 			 * HEAD^^" would be missed.
 			 */
-			common_one = get_merge_bases(lookup_commit(head),
-				j->item, 1);
+			common_one = get_merge_bases(head_commit, j->item, 1);
 			if (hashcmp(common_one->item->object.sha1,
 				j->item->object.sha1)) {
 				up_to_date = 0;
@@ -1302,7 +1482,7 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 		}
 		if (up_to_date) {
 			finish_up_to_date("Already up-to-date. Yeeah!");
-			return 0;
+			goto done;
 		}
 	}
 
@@ -1320,21 +1500,18 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	 * sync with the head commit.  The strategies are responsible
 	 * to ensure this.
 	 */
-	if (use_strategies_nr != 1) {
-		/*
-		 * Stash away the local changes so that we can try more
-		 * than one.
-		 */
-		save_state();
-	} else {
-		memcpy(stash, null_sha1, 20);
-	}
+	if (use_strategies_nr == 1 ||
+	    /*
+	     * Stash away the local changes so that we can try more than one.
+	     */
+	    save_state(stash))
+		hashcpy(stash, null_sha1);
 
 	for (i = 0; i < use_strategies_nr; i++) {
 		int ret;
 		if (i) {
 			printf(_("Rewinding the tree to pristine...\n"));
-			restore_state();
+			restore_state(head_commit->object.sha1, stash);
 		}
 		if (use_strategies_nr != 1)
 			printf(_("Trying merge strategy %s...\n"),
@@ -1346,7 +1523,8 @@ 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,
-			common, head_arg);
+					 common, remoteheads,
+					 head_commit, head_arg);
 		if (!option_commit && !ret) {
 			merge_was_ok = 1;
 			/*
@@ -1387,66 +1565,50 @@ 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)
-		return finish_automerge(common, result_tree, wt_strategy);
+	if (automerge_was_ok) {
+		ret = finish_automerge(head_commit, head_subsumed,
+				       common, remoteheads,
+				       result_tree, wt_strategy);
+		goto done;
+	}
 
 	/*
 	 * Pick the result from the best strategy and have the user fix
 	 * it up.
 	 */
 	if (!best_strategy) {
-		restore_state();
+		restore_state(head_commit->object.sha1, stash);
 		if (use_strategies_nr > 1)
 			fprintf(stderr,
 				_("No merge strategy handled the merge.\n"));
 		else
 			fprintf(stderr, _("Merge with strategy %s failed.\n"),
 				use_strategies[0]->name);
-		return 2;
+		ret = 2;
+		goto done;
 	} else if (best_strategy == wt_strategy)
 		; /* We already have its result in the working tree. */
 	else {
 		printf(_("Rewinding the tree to pristine...\n"));
-		restore_state();
+		restore_state(head_commit->object.sha1, stash);
 		printf(_("Using the %s to prepare resolving by hand.\n"),
 			best_strategy);
-		try_merge_strategy(best_strategy, common, head_arg);
+		try_merge_strategy(best_strategy, common, remoteheads,
+				   head_commit, head_arg);
 	}
 
 	if (squash)
-		finish(NULL, NULL);
-	else {
-		int fd;
-		struct commit_list *j;
-
-		for (j = remoteheads; j; j = j->next)
-			strbuf_addf(&buf, "%s\n",
-				sha1_to_hex(j->item->object.sha1));
-		fd = open(git_path("MERGE_HEAD"), O_WRONLY | O_CREAT, 0666);
-		if (fd < 0)
-			die_errno(_("Could not open '%s' for writing"),
-				  git_path("MERGE_HEAD"));
-		if (write_in_full(fd, buf.buf, buf.len) != buf.len)
-			die_errno(_("Could not write to '%s'"), git_path("MERGE_HEAD"));
-		close(fd);
-		strbuf_addch(&merge_msg, '\n');
-		write_merge_msg();
-		fd = open(git_path("MERGE_MODE"), O_WRONLY | O_CREAT | O_TRUNC, 0666);
-		if (fd < 0)
-			die_errno(_("Could not open '%s' for writing"),
-				  git_path("MERGE_MODE"));
-		strbuf_reset(&buf);
-		if (!allow_fast_forward)
-			strbuf_addf(&buf, "no-ff");
-		if (write_in_full(fd, buf.buf, buf.len) != buf.len)
-			die_errno(_("Could not write to '%s'"), git_path("MERGE_MODE"));
-		close(fd);
-	}
+		finish(head_commit, remoteheads, NULL, NULL);
+	else
+		write_merge_state(remoteheads);
 
-	if (merge_was_ok) {
+	if (merge_was_ok)
 		fprintf(stderr, _("Automatic merge went well; "
 			"stopped before committing as requested\n"));
-		return 0;
-	} else
-		return suggest_conflicts(option_renormalize);
+	else
+		ret = suggest_conflicts(option_renormalize);
+
+done:
+	free(branch_to_free);
+	return ret;
 }