diff --git a/Makefile b/Makefile
index de151638bb5c20..9b52071b7304b5 100644
--- a/Makefile
+++ b/Makefile
@@ -240,7 +240,6 @@ SCRIPT_SH += git-lost-found.sh
 SCRIPT_SH += git-merge-octopus.sh
 SCRIPT_SH += git-merge-one-file.sh
 SCRIPT_SH += git-merge-resolve.sh
-SCRIPT_SH += git-merge.sh
 SCRIPT_SH += git-mergetool.sh
 SCRIPT_SH += git-parse-remote.sh
 SCRIPT_SH += git-pull.sh
@@ -515,6 +514,7 @@ BUILTIN_OBJS += builtin-ls-remote.o
 BUILTIN_OBJS += builtin-ls-tree.o
 BUILTIN_OBJS += builtin-mailinfo.o
 BUILTIN_OBJS += builtin-mailsplit.o
+BUILTIN_OBJS += builtin-merge.o
 BUILTIN_OBJS += builtin-merge-base.o
 BUILTIN_OBJS += builtin-merge-file.o
 BUILTIN_OBJS += builtin-merge-ours.o
diff --git a/alias.c b/alias.c
index 995f3e6a0ac84f..ccb1108c944360 100644
--- a/alias.c
+++ b/alias.c
@@ -21,3 +21,57 @@ char *alias_lookup(const char *alias)
 	git_config(alias_lookup_cb, NULL);
 	return alias_val;
 }
+
+int split_cmdline(char *cmdline, const char ***argv)
+{
+	int src, dst, count = 0, size = 16;
+	char quoted = 0;
+
+	*argv = xmalloc(sizeof(char*) * size);
+
+	/* split alias_string */
+	(*argv)[count++] = cmdline;
+	for (src = dst = 0; cmdline[src];) {
+		char c = cmdline[src];
+		if (!quoted && isspace(c)) {
+			cmdline[dst++] = 0;
+			while (cmdline[++src]
+					&& isspace(cmdline[src]))
+				; /* skip */
+			if (count >= size) {
+				size += 16;
+				*argv = xrealloc(*argv, sizeof(char*) * size);
+			}
+			(*argv)[count++] = cmdline + dst;
+		} else if (!quoted && (c == '\'' || c == '"')) {
+			quoted = c;
+			src++;
+		} else if (c == quoted) {
+			quoted = 0;
+			src++;
+		} else {
+			if (c == '\\' && quoted != '\'') {
+				src++;
+				c = cmdline[src];
+				if (!c) {
+					free(*argv);
+					*argv = NULL;
+					return error("cmdline ends with \\");
+				}
+			}
+			cmdline[dst++] = c;
+			src++;
+		}
+	}
+
+	cmdline[dst] = 0;
+
+	if (quoted) {
+		free(*argv);
+		*argv = NULL;
+		return error("unclosed quote");
+	}
+
+	return count;
+}
+
diff --git a/builtin-commit-tree.c b/builtin-commit-tree.c
index 3881f6c2f56f31..7a9a309be0543d 100644
--- a/builtin-commit-tree.c
+++ b/builtin-commit-tree.c
@@ -45,41 +45,19 @@ static const char commit_utf8_warn[] =
 "You may want to amend it after fixing the message, or set the config\n"
 "variable i18n.commitencoding to the encoding your project uses.\n";
 
-int cmd_commit_tree(int argc, const char **argv, const char *prefix)
+int commit_tree(const char *msg, unsigned char *tree,
+		struct commit_list *parents, unsigned char *ret)
 {
-	int i;
-	struct commit_list *parents = NULL;
-	unsigned char tree_sha1[20];
-	unsigned char commit_sha1[20];
-	struct strbuf buffer;
 	int encoding_is_utf8;
+	struct strbuf buffer;
 
-	git_config(git_default_config, NULL);
-
-	if (argc < 2)
-		usage(commit_tree_usage);
-	if (get_sha1(argv[1], tree_sha1))
-		die("Not a valid object name %s", argv[1]);
-
-	check_valid(tree_sha1, OBJ_TREE);
-	for (i = 2; i < argc; i += 2) {
-		unsigned char sha1[20];
-		const char *a, *b;
-		a = argv[i]; b = argv[i+1];
-		if (!b || strcmp(a, "-p"))
-			usage(commit_tree_usage);
-
-		if (get_sha1(b, sha1))
-			die("Not a valid object name %s", b);
-		check_valid(sha1, OBJ_COMMIT);
-		new_parent(lookup_commit(sha1), &parents);
-	}
+	check_valid(tree, OBJ_TREE);
 
 	/* Not having i18n.commitencoding is the same as having utf-8 */
 	encoding_is_utf8 = is_encoding_utf8(git_commit_encoding);
 
 	strbuf_init(&buffer, 8192); /* should avoid reallocs for the headers */
-	strbuf_addf(&buffer, "tree %s\n", sha1_to_hex(tree_sha1));
+	strbuf_addf(&buffer, "tree %s\n", sha1_to_hex(tree));
 
 	/*
 	 * NOTE! This ordering means that the same exact tree merged with a
@@ -102,14 +80,47 @@ int cmd_commit_tree(int argc, const char **argv, const char *prefix)
 	strbuf_addch(&buffer, '\n');
 
 	/* And add the comment */
-	if (strbuf_read(&buffer, 0, 0) < 0)
-		die("git-commit-tree: read returned %s", strerror(errno));
+	strbuf_addstr(&buffer, msg);
 
 	/* And check the encoding */
 	if (encoding_is_utf8 && !is_utf8(buffer.buf))
 		fprintf(stderr, commit_utf8_warn);
 
-	if (!write_sha1_file(buffer.buf, buffer.len, commit_type, commit_sha1)) {
+	return write_sha1_file(buffer.buf, buffer.len, commit_type, ret);
+}
+
+int cmd_commit_tree(int argc, const char **argv, const char *prefix)
+{
+	int i;
+	struct commit_list *parents = NULL;
+	unsigned char tree_sha1[20];
+	unsigned char commit_sha1[20];
+	struct strbuf buffer = STRBUF_INIT;
+
+	git_config(git_default_config, NULL);
+
+	if (argc < 2)
+		usage(commit_tree_usage);
+	if (get_sha1(argv[1], tree_sha1))
+		die("Not a valid object name %s", argv[1]);
+
+	for (i = 2; i < argc; i += 2) {
+		unsigned char sha1[20];
+		const char *a, *b;
+		a = argv[i]; b = argv[i+1];
+		if (!b || strcmp(a, "-p"))
+			usage(commit_tree_usage);
+
+		if (get_sha1(b, sha1))
+			die("Not a valid object name %s", b);
+		check_valid(sha1, OBJ_COMMIT);
+		new_parent(lookup_commit(sha1), &parents);
+	}
+
+	if (strbuf_read(&buffer, 0, 0) < 0)
+		die("git-commit-tree: read returned %s", strerror(errno));
+
+	if (!commit_tree(buffer.buf, tree_sha1, parents, commit_sha1)) {
 		printf("%s\n", sha1_to_hex(commit_sha1));
 		return 0;
 	}
diff --git a/builtin-fmt-merge-msg.c b/builtin-fmt-merge-msg.c
index b892621ab50346..dbd7d2ddae2d4b 100644
--- a/builtin-fmt-merge-msg.c
+++ b/builtin-fmt-merge-msg.c
@@ -159,23 +159,24 @@ static int handle_line(char *line)
 }
 
 static void print_joined(const char *singular, const char *plural,
-		struct list *list)
+		struct list *list, struct strbuf *out)
 {
 	if (list->nr == 0)
 		return;
 	if (list->nr == 1) {
-		printf("%s%s", singular, list->list[0]);
+		strbuf_addf(out, "%s%s", singular, list->list[0]);
 	} else {
 		int i;
-		printf("%s", plural);
+		strbuf_addstr(out, plural);
 		for (i = 0; i < list->nr - 1; i++)
-			printf("%s%s", i > 0 ? ", " : "", list->list[i]);
-		printf(" and %s", list->list[list->nr - 1]);
+			strbuf_addf(out, "%s%s", i > 0 ? ", " : "", list->list[i]);
+		strbuf_addf(out, " and %s", list->list[list->nr - 1]);
 	}
 }
 
 static void shortlog(const char *name, unsigned char *sha1,
-		struct commit *head, struct rev_info *rev, int limit)
+		struct commit *head, struct rev_info *rev, int limit,
+		struct strbuf *out)
 {
 	int i, count = 0;
 	struct commit *commit;
@@ -232,15 +233,15 @@ static void shortlog(const char *name, unsigned char *sha1,
 	}
 
 	if (count > limit)
-		printf("\n* %s: (%d commits)\n", name, count);
+		strbuf_addf(out, "\n* %s: (%d commits)\n", name, count);
 	else
-		printf("\n* %s:\n", name);
+		strbuf_addf(out, "\n* %s:\n", name);
 
 	for (i = 0; i < subjects.nr; i++)
 		if (i >= limit)
-			printf("  ...\n");
+			strbuf_addf(out, "  ...\n");
 		else
-			printf("  %s\n", subjects.list[i]);
+			strbuf_addf(out, "  %s\n", subjects.list[i]);
 
 	clear_commit_marks((struct commit *)branch, flags);
 	clear_commit_marks(head, flags);
@@ -251,43 +252,13 @@ static void shortlog(const char *name, unsigned char *sha1,
 	free_list(&subjects);
 }
 
-int cmd_fmt_merge_msg(int argc, const char **argv, const char *prefix)
-{
-	int limit = 20, i = 0;
+int fmt_merge_msg(int merge_summary, struct strbuf *in, struct strbuf *out) {
+	int limit = 20, i = 0, pos = 0;
 	char line[1024];
-	FILE *in = stdin;
-	const char *sep = "";
+	char *p = line, *sep = "";
 	unsigned char head_sha1[20];
 	const char *current_branch;
 
-	git_config(fmt_merge_msg_config, NULL);
-
-	while (argc > 1) {
-		if (!strcmp(argv[1], "--log") || !strcmp(argv[1], "--summary"))
-			merge_summary = 1;
-		else if (!strcmp(argv[1], "--no-log")
-				|| !strcmp(argv[1], "--no-summary"))
-			merge_summary = 0;
-		else if (!strcmp(argv[1], "-F") || !strcmp(argv[1], "--file")) {
-			if (argc < 3)
-				die ("Which file?");
-			if (!strcmp(argv[2], "-"))
-				in = stdin;
-			else {
-				fclose(in);
-				in = fopen(argv[2], "r");
-				if (!in)
-					die("cannot open %s", argv[2]);
-			}
-			argc--; argv++;
-		} else
-			break;
-		argc--; argv++;
-	}
-
-	if (argc > 1)
-		usage(fmt_merge_msg_usage);
-
 	/* get current branch */
 	current_branch = resolve_ref("HEAD", head_sha1, 1, NULL);
 	if (!current_branch)
@@ -295,75 +266,127 @@ int cmd_fmt_merge_msg(int argc, const char **argv, const char *prefix)
 	if (!prefixcmp(current_branch, "refs/heads/"))
 		current_branch += 11;
 
-	while (fgets(line, sizeof(line), in)) {
+	/* get a line */
+	while (pos < in->len) {
+		int len;
+		char *newline;
+
+		p = in->buf + pos;
+		newline = strchr(p, '\n');
+		len = newline ? newline - p : strlen(p);
+		pos += len + !!newline;
 		i++;
-		if (line[0] == 0)
-			continue;
-		if (handle_line(line))
-			die ("Error in line %d: %s", i, line);
+		p[len] = 0;
+		if (handle_line(p))
+			die ("Error in line %d: %.*s", i, len, p);
 	}
 
-	printf("Merge ");
+	strbuf_addstr(out, "Merge ");
 	for (i = 0; i < srcs.nr; i++) {
 		struct src_data *src_data = srcs.payload[i];
 		const char *subsep = "";
 
-		printf(sep);
+		strbuf_addstr(out, sep);
 		sep = "; ";
 
 		if (src_data->head_status == 1) {
-			printf(srcs.list[i]);
+			strbuf_addstr(out, srcs.list[i]);
 			continue;
 		}
 		if (src_data->head_status == 3) {
 			subsep = ", ";
-			printf("HEAD");
+			strbuf_addstr(out, "HEAD");
 		}
 		if (src_data->branch.nr) {
-			printf(subsep);
+			strbuf_addstr(out, subsep);
 			subsep = ", ";
-			print_joined("branch ", "branches ", &src_data->branch);
+			print_joined("branch ", "branches ", &src_data->branch,
+					out);
 		}
 		if (src_data->r_branch.nr) {
-			printf(subsep);
+			strbuf_addstr(out, subsep);
 			subsep = ", ";
 			print_joined("remote branch ", "remote branches ",
-					&src_data->r_branch);
+					&src_data->r_branch, out);
 		}
 		if (src_data->tag.nr) {
-			printf(subsep);
+			strbuf_addstr(out, subsep);
 			subsep = ", ";
-			print_joined("tag ", "tags ", &src_data->tag);
+			print_joined("tag ", "tags ", &src_data->tag, out);
 		}
 		if (src_data->generic.nr) {
-			printf(subsep);
-			print_joined("commit ", "commits ", &src_data->generic);
+			strbuf_addstr(out, subsep);
+			print_joined("commit ", "commits ", &src_data->generic,
+					out);
 		}
 		if (strcmp(".", srcs.list[i]))
-			printf(" of %s", srcs.list[i]);
+			strbuf_addf(out, " of %s", srcs.list[i]);
 	}
 
 	if (!strcmp("master", current_branch))
-		putchar('\n');
+		strbuf_addch(out, '\n');
 	else
-		printf(" into %s\n", current_branch);
+		strbuf_addf(out, " into %s\n", current_branch);
 
 	if (merge_summary) {
 		struct commit *head;
 		struct rev_info rev;
 
 		head = lookup_commit(head_sha1);
-		init_revisions(&rev, prefix);
+		init_revisions(&rev, NULL);
 		rev.commit_format = CMIT_FMT_ONELINE;
 		rev.ignore_merges = 1;
 		rev.limited = 1;
 
 		for (i = 0; i < origins.nr; i++)
 			shortlog(origins.list[i], origins.payload[i],
-					head, &rev, limit);
+					head, &rev, limit, out);
 	}
+	return 0;
+}
+
+int cmd_fmt_merge_msg(int argc, const char **argv, const char *prefix)
+{
+	FILE *in = stdin;
+	struct strbuf input, output;
+	int ret;
+
+	git_config(fmt_merge_msg_config, NULL);
+
+	while (argc > 1) {
+		if (!strcmp(argv[1], "--log") || !strcmp(argv[1], "--summary"))
+			merge_summary = 1;
+		else if (!strcmp(argv[1], "--no-log")
+				|| !strcmp(argv[1], "--no-summary"))
+			merge_summary = 0;
+		else if (!strcmp(argv[1], "-F") || !strcmp(argv[1], "--file")) {
+			if (argc < 3)
+				die ("Which file?");
+			if (!strcmp(argv[2], "-"))
+				in = stdin;
+			else {
+				fclose(in);
+				in = fopen(argv[2], "r");
+				if (!in)
+					die("cannot open %s", argv[2]);
+			}
+			argc--; argv++;
+		} else
+			break;
+		argc--; argv++;
+	}
+
+	if (argc > 1)
+		usage(fmt_merge_msg_usage);
 
-	/* No cleanup yet; is standalone anyway */
+	strbuf_init(&input, 0);
+	if (strbuf_read(&input, fileno(in), 0) < 0)
+		die("could not read input file %s", strerror(errno));
+	strbuf_init(&output, 0);
 
+	ret = fmt_merge_msg(merge_summary, &input, &output);
+	if (ret)
+		return ret;
+	printf("%s", output.buf);
 	return 0;
 }
diff --git a/builtin-merge-recursive.c b/builtin-merge-recursive.c
index 43bf6aa45eeacb..3731853f83be37 100644
--- a/builtin-merge-recursive.c
+++ b/builtin-merge-recursive.c
@@ -42,14 +42,6 @@ static struct tree *shift_tree_object(struct tree *one, struct tree *two)
  * - *(int *)commit->object.sha1 set to the virtual id.
  */
 
-static unsigned commit_list_count(const struct commit_list *l)
-{
-	unsigned c = 0;
-	for (; l; l = l->next )
-		c++;
-	return c;
-}
-
 static struct commit *make_virtual_commit(struct tree *tree, const char *comment)
 {
 	struct commit *commit = xcalloc(1, sizeof(struct commit));
diff --git a/builtin-merge.c b/builtin-merge.c
new file mode 100644
index 00000000000000..129b4e62dd3bc3
--- /dev/null
+++ b/builtin-merge.c
@@ -0,0 +1,1156 @@
+/*
+ * Builtin "git merge"
+ *
+ * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
+ *
+ * Based on git-merge.sh by Junio C Hamano.
+ */
+
+#include "cache.h"
+#include "parse-options.h"
+#include "builtin.h"
+#include "run-command.h"
+#include "diff.h"
+#include "refs.h"
+#include "commit.h"
+#include "diffcore.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"
+
+#define DEFAULT_TWOHEAD (1<<0)
+#define DEFAULT_OCTOPUS (1<<1)
+#define NO_FAST_FORWARD (1<<2)
+#define NO_TRIVIAL      (1<<3)
+
+struct strategy {
+	const char *name;
+	unsigned attr;
+};
+
+static const char * const builtin_merge_usage[] = {
+	"git-merge [options] <remote>...",
+	"git-merge [options] <msg> HEAD <remote>",
+	NULL
+};
+
+static int show_diffstat = 1, option_log, squash;
+static int option_commit = 1, allow_fast_forward = 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 struct strategy **use_strategies;
+static size_t use_strategies_nr, use_strategies_alloc;
+static const char *branch;
+
+static struct strategy all_strategy[] = {
+	{ "recur",      NO_TRIVIAL },
+	{ "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
+	{ "octopus",    DEFAULT_OCTOPUS },
+	{ "resolve",    0 },
+	{ "stupid",     0 },
+	{ "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
+	{ "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
+};
+
+static const char *pull_twohead, *pull_octopus;
+
+static int option_parse_message(const struct option *opt,
+				const char *arg, int unset)
+{
+	struct strbuf *buf = opt->value;
+
+	if (unset)
+		strbuf_setlen(buf, 0);
+	else {
+		strbuf_addf(buf, "%s\n\n", arg);
+		have_message = 1;
+	}
+	return 0;
+}
+
+static struct strategy *get_strategy(const char *name)
+{
+	int i;
+
+	if (!name)
+		return NULL;
+
+	for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
+		if (!strcmp(name, all_strategy[i].name))
+			return &all_strategy[i];
+	return NULL;
+}
+
+static void append_strategy(struct strategy *s)
+{
+	ALLOC_GROW(use_strategies, use_strategies_nr + 1, use_strategies_alloc);
+	use_strategies[use_strategies_nr++] = s;
+}
+
+static int option_parse_strategy(const struct option *opt,
+				 const char *name, int unset)
+{
+	int i;
+	struct strategy *s;
+
+	if (unset)
+		return 0;
+
+	s = get_strategy(name);
+
+	if (s)
+		append_strategy(s);
+	else {
+		struct strbuf err;
+		strbuf_init(&err, 0);
+		for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
+			strbuf_addf(&err, " %s", all_strategy[i].name);
+		fprintf(stderr, "Could not find merge strategy '%s'.\n", name);
+		fprintf(stderr, "Available strategies are:%s.\n", err.buf);
+		exit(1);
+	}
+	return 0;
+}
+
+static int option_parse_n(const struct option *opt,
+			  const char *arg, int unset)
+{
+	show_diffstat = unset;
+	return 0;
+}
+
+static struct option builtin_merge_options[] = {
+	{ OPTION_CALLBACK, 'n', NULL, NULL, NULL,
+		"do not show a diffstat at the end of the merge",
+		PARSE_OPT_NOARG, option_parse_n },
+	OPT_BOOLEAN(0, "stat", &show_diffstat,
+		"show a diffstat at the end of the merge"),
+	OPT_BOOLEAN(0, "summary", &show_diffstat, "(synonym to --stat)"),
+	OPT_BOOLEAN(0, "log", &option_log,
+		"add list of one-line log to merge commit message"),
+	OPT_BOOLEAN(0, "squash", &squash,
+		"create a single commit instead of doing a merge"),
+	OPT_BOOLEAN(0, "commit", &option_commit,
+		"perform a commit if the merge succeeds (default)"),
+	OPT_BOOLEAN(0, "ff", &allow_fast_forward,
+		"allow fast forward (default)"),
+	OPT_CALLBACK('s', "strategy", &use_strategies, "strategy",
+		"merge strategy to use", option_parse_strategy),
+	OPT_CALLBACK('m', "message", &merge_msg, "message",
+		"message to be used for the merge commit (if any)",
+		option_parse_message),
+	OPT_END()
+};
+
+/* Cleans up metadata that is uninteresting after a succeeded merge. */
+static void drop_save(void)
+{
+	unlink(git_path("MERGE_HEAD"));
+	unlink(git_path("MERGE_MSG"));
+}
+
+static void save_state(void)
+{
+	int len;
+	struct child_process cp;
+	struct strbuf buffer = STRBUF_INIT;
+	const char *argv[] = {"stash", "create", NULL};
+
+	memset(&cp, 0, sizeof(cp));
+	cp.argv = argv;
+	cp.out = -1;
+	cp.git_cmd = 1;
+
+	if (start_command(&cp))
+		die("could not run stash.");
+	len = strbuf_read(&buffer, cp.out, 1024);
+	close(cp.out);
+
+	if (finish_command(&cp) || len < 0)
+		die("stash failed");
+	else if (!len)
+		return;
+	strbuf_setlen(&buffer, buffer.len-1);
+	if (get_sha1(buffer.buf, stash))
+		die("not a valid object: %s", buffer.buf);
+}
+
+static void reset_hard(unsigned const char *sha1, int verbose)
+{
+	int i = 0;
+	const char *args[6];
+
+	args[i++] = "read-tree";
+	if (verbose)
+		args[i++] = "-v";
+	args[i++] = "--reset";
+	args[i++] = "-u";
+	args[i++] = sha1_to_hex(sha1);
+	args[i] = NULL;
+
+	if (run_command_v_opt(args, RUN_GIT_CMD))
+		die("read-tree failed");
+}
+
+static void restore_state(void)
+{
+	struct strbuf sb;
+	const char *args[] = { "stash", "apply", NULL, NULL };
+
+	if (is_null_sha1(stash))
+		return;
+
+	reset_hard(head, 1);
+
+	strbuf_init(&sb, 0);
+	args[2] = sha1_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);
+
+	strbuf_release(&sb);
+	refresh_cache(REFRESH_QUIET);
+}
+
+/* This is called when no merge was necessary. */
+static void finish_up_to_date(const char *msg)
+{
+	printf("%s%s\n", squash ? " (nothing to squash)" : "", msg);
+	drop_save();
+}
+
+static void squash_message(void)
+{
+	struct rev_info rev;
+	struct commit *commit;
+	struct strbuf out;
+	struct commit_list *j;
+	int fd;
+
+	printf("Squash commit -- not updating HEAD\n");
+	fd = open(git_path("SQUASH_MSG"), O_WRONLY | O_CREAT, 0666);
+	if (fd < 0)
+		die("Could not write to %s", git_path("SQUASH_MSG"));
+
+	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);
+
+	for (j = remoteheads; j; j = j->next)
+		add_pending_object(&rev, &j->item->object, NULL);
+
+	setup_revisions(0, NULL, &rev, NULL);
+	if (prepare_revision_walk(&rev))
+		die("revision walk setup failed");
+
+	strbuf_init(&out, 0);
+	strbuf_addstr(&out, "Squashed commit of the following:\n");
+	while ((commit = get_revision(&rev)) != NULL) {
+		strbuf_addch(&out, '\n');
+		strbuf_addf(&out, "commit %s\n",
+			sha1_to_hex(commit->object.sha1));
+		pretty_print_commit(rev.commit_format, commit, &out, rev.abbrev,
+			NULL, NULL, rev.date_mode, 0);
+	}
+	write(fd, out.buf, out.len);
+	close(fd);
+	strbuf_release(&out);
+}
+
+static int run_hook(const char *name)
+{
+	struct child_process hook;
+	const char *argv[3], *env[2];
+	char index[PATH_MAX];
+
+	argv[0] = git_path("hooks/%s", name);
+	if (access(argv[0], X_OK) < 0)
+		return 0;
+
+	snprintf(index, sizeof(index), "GIT_INDEX_FILE=%s", get_index_file());
+	env[0] = index;
+	env[1] = NULL;
+
+	if (squash)
+		argv[1] = "1";
+	else
+		argv[1] = "0";
+	argv[2] = NULL;
+
+	memset(&hook, 0, sizeof(hook));
+	hook.argv = argv;
+	hook.no_stdin = 1;
+	hook.stdout_to_stderr = 1;
+	hook.env = env;
+
+	return run_command(&hook);
+}
+
+static void finish(const unsigned char *new_head, const char *msg)
+{
+	struct strbuf reflog_message;
+
+	strbuf_init(&reflog_message, 0);
+	if (!msg)
+		strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
+	else {
+		printf("%s\n", msg);
+		strbuf_addf(&reflog_message, "%s: %s",
+			getenv("GIT_REFLOG_ACTION"), msg);
+	}
+	if (squash) {
+		squash_message();
+	} else {
+		if (!merge_msg.len)
+			printf("No merge message -- not updating HEAD\n");
+		else {
+			const char *argv_gc_auto[] = { "gc", "--auto", NULL };
+			update_ref(reflog_message.buf, "HEAD",
+				new_head, head, 0,
+				DIE_ON_ERR);
+			/*
+			 * We ignore errors in 'gc --auto', since the
+			 * user should see them.
+			 */
+			run_command_v_opt(argv_gc_auto, RUN_GIT_CMD);
+		}
+	}
+	if (new_head && show_diffstat) {
+		struct diff_options opts;
+		diff_setup(&opts);
+		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);
+		diffcore_std(&opts);
+		diff_flush(&opts);
+	}
+
+	/* Run a post-merge hook */
+	run_hook("post-merge");
+
+	strbuf_release(&reflog_message);
+}
+
+/* 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 strbuf buf;
+	const char *ptr;
+	int len, early;
+
+	memset(branch_head, 0, sizeof(branch_head));
+	remote_head = peel_to_type(remote, 0, NULL, OBJ_COMMIT);
+	if (!remote_head)
+		die("'%s' does not point to a commit", remote);
+
+	strbuf_init(&buf, 0);
+	strbuf_addstr(&buf, "refs/heads/");
+	strbuf_addstr(&buf, remote);
+	resolve_ref(buf.buf, branch_head, 0, 0);
+
+	if (!hashcmp(remote_head->sha1, branch_head)) {
+		strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
+			sha1_to_hex(branch_head), remote);
+		return;
+	}
+
+	/* See if remote matches <name>^^^.. or <name>~<number> */
+	for (len = 0, ptr = remote + strlen(remote);
+	     remote < ptr && ptr[-1] == '^';
+	     ptr--)
+		len++;
+	if (len)
+		early = 1;
+	else {
+		early = 0;
+		ptr = strrchr(remote, '~');
+		if (ptr) {
+			int seen_nonzero = 0;
+
+			len++; /* count ~ */
+			while (*++ptr && isdigit(*ptr)) {
+				seen_nonzero |= (*ptr != '0');
+				len++;
+			}
+			if (*ptr)
+				len = 0; /* not ...~<number> */
+			else if (seen_nonzero)
+				early = 1;
+			else if (len == 1)
+				early = 1; /* "name~" is "name~1"! */
+		}
+	}
+	if (len) {
+		struct strbuf truname = STRBUF_INIT;
+		strbuf_addstr(&truname, "refs/heads/");
+		strbuf_addstr(&truname, remote);
+		strbuf_setlen(&truname, len+11);
+		if (resolve_ref(truname.buf, buf_sha, 0, 0)) {
+			strbuf_addf(msg,
+				    "%s\t\tbranch '%s'%s of .\n",
+				    sha1_to_hex(remote_head->sha1),
+				    truname.buf,
+				    (early ? " (early part)" : ""));
+			return;
+		}
+	}
+
+	if (!strcmp(remote, "FETCH_HEAD") &&
+			!access(git_path("FETCH_HEAD"), R_OK)) {
+		FILE *fp;
+		struct strbuf line;
+		char *ptr;
+
+		strbuf_init(&line, 0);
+		fp = fopen(git_path("FETCH_HEAD"), "r");
+		if (!fp)
+			die("could not open %s for reading: %s",
+				git_path("FETCH_HEAD"), strerror(errno));
+		strbuf_getline(&line, fp, '\n');
+		fclose(fp);
+		ptr = strstr(line.buf, "\tnot-for-merge\t");
+		if (ptr)
+			strbuf_remove(&line, ptr-line.buf+1, 13);
+		strbuf_addbuf(msg, &line);
+		strbuf_release(&line);
+		return;
+	}
+	strbuf_addf(msg, "%s\t\tcommit '%s'\n",
+		sha1_to_hex(remote_head->sha1), remote);
+}
+
+int git_merge_config(const char *k, const char *v, void *cb)
+{
+	if (branch && !prefixcmp(k, "branch.") &&
+		!prefixcmp(k + 7, branch) &&
+		!strcmp(k + 7 + strlen(branch), ".mergeoptions")) {
+		const char **argv;
+		int argc;
+		char *buf;
+
+		buf = xstrdup(v);
+		argc = split_cmdline(buf, &argv);
+		argv = xrealloc(argv, sizeof(*argv) * (argc + 2));
+		memmove(argv + 1, argv, sizeof(*argv) * (argc + 1));
+		argc++;
+		parse_options(argc, argv, builtin_merge_options,
+			      builtin_merge_usage, 0);
+		free(buf);
+	}
+
+	if (!strcmp(k, "merge.diffstat") || !strcmp(k, "merge.stat"))
+		show_diffstat = git_config_bool(k, v);
+	else if (!strcmp(k, "pull.twohead"))
+		return git_config_string(&pull_twohead, k, v);
+	else if (!strcmp(k, "pull.octopus"))
+		return git_config_string(&pull_octopus, k, v);
+	else if (!strcmp(k, "merge.log") || !strcmp(k, "merge.summary"))
+		option_log = git_config_bool(k, v);
+	return git_diff_ui_config(k, v, cb);
+}
+
+static int read_tree_trivial(unsigned char *common, unsigned char *head,
+			     unsigned char *one)
+{
+	int i, nr_trees = 0;
+	struct tree *trees[MAX_UNPACK_TREES];
+	struct tree_desc t[MAX_UNPACK_TREES];
+	struct unpack_trees_options opts;
+
+	memset(&opts, 0, sizeof(opts));
+	opts.head_idx = 2;
+	opts.src_index = &the_index;
+	opts.dst_index = &the_index;
+	opts.update = 1;
+	opts.verbose_update = 1;
+	opts.trivial_merges_only = 1;
+	opts.merge = 1;
+	trees[nr_trees] = parse_tree_indirect(common);
+	if (!trees[nr_trees++])
+		return -1;
+	trees[nr_trees] = parse_tree_indirect(head);
+	if (!trees[nr_trees++])
+		return -1;
+	trees[nr_trees] = parse_tree_indirect(one);
+	if (!trees[nr_trees++])
+		return -1;
+	opts.fn = threeway_merge;
+	cache_tree_free(&active_cache_tree);
+	for (i = 0; i < nr_trees; i++) {
+		parse_tree(trees[i]);
+		init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
+	}
+	if (unpack_trees(nr_trees, t, &opts))
+		return -1;
+	return 0;
+}
+
+static void write_tree_trivial(unsigned char *sha1)
+{
+	if (write_cache_as_tree(sha1, 0, NULL))
+		die("git write-tree failed to write a tree");
+}
+
+static int try_merge_strategy(const char *strategy, struct commit_list *common,
+			      const char *head_arg)
+{
+	const char **args;
+	int i = 0, ret;
+	struct commit_list *j;
+	struct strbuf buf;
+
+	args = xmalloc((4 + commit_list_count(common) +
+			commit_list_count(remoteheads)) * sizeof(char *));
+	strbuf_init(&buf, 0);
+	strbuf_addf(&buf, "merge-%s", strategy);
+	args[i++] = buf.buf;
+	for (j = common; j; j = j->next)
+		args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
+	args[i++] = "--";
+	args[i++] = head_arg;
+	for (j = remoteheads; j; j = j->next)
+		args[i++] = xstrdup(sha1_to_hex(j->item->object.sha1));
+	args[i] = NULL;
+	ret = run_command_v_opt(args, RUN_GIT_CMD);
+	strbuf_release(&buf);
+	i = 1;
+	for (j = common; j; j = j->next)
+		free((void *)args[i++]);
+	i += 2;
+	for (j = remoteheads; j; j = j->next)
+		free((void *)args[i++]);
+	free(args);
+	return -ret;
+}
+
+static void count_diff_files(struct diff_queue_struct *q,
+			     struct diff_options *opt, void *data)
+{
+	int *count = data;
+
+	(*count) += q->nr;
+}
+
+static int count_unmerged_entries(void)
+{
+	const struct index_state *state = &the_index;
+	int i, ret = 0;
+
+	for (i = 0; i < state->cache_nr; i++)
+		if (ce_stage(state->cache[i]))
+			ret++;
+
+	return ret;
+}
+
+static int checkout_fast_forward(unsigned char *head, unsigned char *remote)
+{
+	struct tree *trees[MAX_UNPACK_TREES];
+	struct unpack_trees_options opts;
+	struct tree_desc t[MAX_UNPACK_TREES];
+	int i, fd, nr_trees = 0;
+	struct dir_struct dir;
+	struct lock_file *lock_file = xcalloc(1, sizeof(struct lock_file));
+
+	if (read_cache_unmerged())
+		die("you need to resolve your current index first");
+
+	fd = hold_locked_index(lock_file, 1);
+
+	memset(&trees, 0, sizeof(trees));
+	memset(&opts, 0, sizeof(opts));
+	memset(&t, 0, sizeof(t));
+	dir.show_ignored = 1;
+	dir.exclude_per_dir = ".gitignore";
+	opts.dir = &dir;
+
+	opts.head_idx = 1;
+	opts.src_index = &the_index;
+	opts.dst_index = &the_index;
+	opts.update = 1;
+	opts.verbose_update = 1;
+	opts.merge = 1;
+	opts.fn = twoway_merge;
+
+	trees[nr_trees] = parse_tree_indirect(head);
+	if (!trees[nr_trees++])
+		return -1;
+	trees[nr_trees] = parse_tree_indirect(remote);
+	if (!trees[nr_trees++])
+		return -1;
+	for (i = 0; i < nr_trees; i++) {
+		parse_tree(trees[i]);
+		init_tree_desc(t+i, trees[i]->buffer, trees[i]->size);
+	}
+	if (unpack_trees(nr_trees, t, &opts))
+		return -1;
+	if (write_cache(fd, active_cache, active_nr) ||
+		commit_locked_index(lock_file))
+		die("unable to write new index file");
+	return 0;
+}
+
+static void split_merge_strategies(const char *string, struct strategy **list,
+				   int *nr, int *alloc)
+{
+	char *p, *q, *buf;
+
+	if (!string)
+		return;
+
+	buf = xstrdup(string);
+	q = buf;
+	for (;;) {
+		p = strchr(q, ' ');
+		if (!p) {
+			ALLOC_GROW(*list, *nr + 1, *alloc);
+			(*list)[(*nr)++].name = xstrdup(q);
+			free(buf);
+			return;
+		} else {
+			*p = '\0';
+			ALLOC_GROW(*list, *nr + 1, *alloc);
+			(*list)[(*nr)++].name = xstrdup(q);
+			q = ++p;
+		}
+	}
+}
+
+static void add_strategies(const char *string, unsigned attr)
+{
+	struct strategy *list = NULL;
+	int list_alloc = 0, list_nr = 0, i;
+
+	memset(&list, 0, sizeof(list));
+	split_merge_strategies(string, &list, &list_nr, &list_alloc);
+	if (list != NULL) {
+		for (i = 0; i < list_nr; i++) {
+			struct strategy *s;
+
+			s = get_strategy(list[i].name);
+			if (s)
+				append_strategy(s);
+		}
+		return;
+	}
+	for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
+		if (all_strategy[i].attr & attr)
+			append_strategy(&all_strategy[i]);
+
+}
+
+static int merge_trivial(void)
+{
+	unsigned char result_tree[20], result_commit[20];
+	struct commit_list parent;
+
+	write_tree_trivial(result_tree);
+	printf("Wonderful.\n");
+	parent.item = remoteheads->item;
+	parent.next = NULL;
+	commit_tree(merge_msg.buf, result_tree, &parent, result_commit);
+	finish(result_commit, "In-index merge");
+	drop_save();
+	return 0;
+}
+
+static int finish_automerge(struct commit_list *common,
+			    unsigned char *result_tree,
+			    const char *wt_strategy)
+{
+	struct commit_list *parents = NULL, *j;
+	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);
+	strbuf_addch(&merge_msg, '\n');
+	commit_tree(merge_msg.buf, result_tree, parents, result_commit);
+	strbuf_addf(&buf, "Merge made by %s.", wt_strategy);
+	finish(result_commit, buf.buf);
+	strbuf_release(&buf);
+	drop_save();
+	return 0;
+}
+
+static int suggest_conflicts(void)
+{
+	FILE *fp;
+	int pos;
+
+	fp = fopen(git_path("MERGE_MSG"), "a");
+	if (!fp)
+		die("Could open %s for writing", git_path("MERGE_MSG"));
+	fprintf(fp, "\nConflicts:\n");
+	for (pos = 0; pos < active_nr; pos++) {
+		struct cache_entry *ce = active_cache[pos];
+
+		if (ce_stage(ce)) {
+			fprintf(fp, "\t%s\n", ce->name);
+			while (pos + 1 < active_nr &&
+					!strcmp(ce->name,
+						active_cache[pos + 1]->name))
+				pos++;
+		}
+	}
+	fclose(fp);
+	rerere();
+	printf("Automatic merge failed; "
+			"fix conflicts and then commit the result.\n");
+	return 1;
+}
+
+static struct commit *is_old_style_invocation(int argc, const char **argv)
+{
+	struct commit *second_token = NULL;
+	if (argc > 1) {
+		unsigned char second_sha1[20];
+
+		if (get_sha1(argv[1], second_sha1))
+			return NULL;
+		second_token = lookup_commit_reference_gently(second_sha1, 0);
+		if (!second_token)
+			die("'%s' is not a commit", argv[1]);
+		if (hashcmp(second_token->object.sha1, head))
+			return NULL;
+	}
+	return second_token;
+}
+
+static int evaluate_result(void)
+{
+	int cnt = 0;
+	struct rev_info rev;
+
+	if (read_cache() < 0)
+		die("failed to read the cache");
+
+	/* Check how many files differ. */
+	init_revisions(&rev, "");
+	setup_revisions(0, NULL, &rev, NULL);
+	rev.diffopt.output_format |=
+		DIFF_FORMAT_CALLBACK;
+	rev.diffopt.format_callback = count_diff_files;
+	rev.diffopt.format_callback_data = &cnt;
+	run_diff_files(&rev, 0);
+
+	/*
+	 * Check how many unmerged entries are
+	 * there.
+	 */
+	cnt += count_unmerged_entries();
+
+	return cnt;
+}
+
+int cmd_merge(int argc, const char **argv, const char *prefix)
+{
+	unsigned char result_tree[20];
+	struct strbuf buf;
+	const char *head_arg;
+	int flag, head_invalid = 0, i;
+	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;
+
+	setup_work_tree();
+	if (unmerged_cache())
+		die("You are in the middle of a conflicted merge.");
+
+	/*
+	 * Check if we are _not_ on a detached HEAD, i.e. if there is a
+	 * current branch.
+	 */
+	branch = resolve_ref("HEAD", head, 0, &flag);
+	if (branch && !prefixcmp(branch, "refs/heads/"))
+		branch += 11;
+	if (is_null_sha1(head))
+		head_invalid = 1;
+
+	git_config(git_merge_config, NULL);
+
+	/* for color.ui */
+	if (diff_use_color_default == -1)
+		diff_use_color_default = git_use_color_default;
+
+	argc = parse_options(argc, argv, builtin_merge_options,
+			builtin_merge_usage, 0);
+
+	if (squash) {
+		if (!allow_fast_forward)
+			die("You cannot combine --squash with --no-ff.");
+		option_commit = 0;
+	}
+
+	if (!argc)
+		usage_with_options(builtin_merge_usage,
+			builtin_merge_options);
+
+	/*
+	 * This could be traditional "merge <msg> HEAD <commit>..."  and
+	 * the way we can tell it is to see if the second token is HEAD,
+	 * but some people might have misused the interface and used a
+	 * committish that is the same as HEAD there instead.
+	 * Traditional format never would have "-m" so it is an
+	 * additional safety measure to check for it.
+	 */
+	strbuf_init(&buf, 0);
+
+	if (!have_message && is_old_style_invocation(argc, argv)) {
+		strbuf_addstr(&merge_msg, argv[0]);
+		head_arg = argv[1];
+		argv += 2;
+		argc -= 2;
+	} else if (head_invalid) {
+		struct object *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.
+		 * We do the same for "git pull".
+		 */
+		if (argc != 1)
+			die("Can merge only exactly one commit into "
+				"empty head");
+		remote_head = peel_to_type(argv[0], 0, NULL, OBJ_COMMIT);
+		if (!remote_head)
+			die("%s - not something we can merge", argv[0]);
+		update_ref("initial pull", "HEAD", remote_head->sha1, NULL, 0,
+				DIE_ON_ERR);
+		reset_hard(remote_head->sha1, 0);
+		return 0;
+	} else {
+		struct strbuf msg;
+
+		/* We are invoked directly as the first-class UI. */
+		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.
+		 */
+		strbuf_init(&msg, 0);
+		for (i = 0; i < argc; i++)
+			merge_name(argv[i], &msg);
+		fmt_merge_msg(option_log, &msg, &merge_msg);
+		if (merge_msg.len)
+			strbuf_setlen(&merge_msg, merge_msg.len-1);
+	}
+
+	if (head_invalid || !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]);
+	setenv("GIT_REFLOG_ACTION", buf.buf, 0);
+	strbuf_reset(&buf);
+
+	for (i = 0; i < argc; i++) {
+		struct object *o;
+
+		o = peel_to_type(argv[i], 0, NULL, OBJ_COMMIT);
+		if (!o)
+			die("%s - not something we can merge", argv[i]);
+		remotes = &commit_list_insert(lookup_commit(o->sha1),
+			remotes)->next;
+
+		strbuf_addf(&buf, "GITHEAD_%s", sha1_to_hex(o->sha1));
+		setenv(buf.buf, argv[i], 1);
+		strbuf_reset(&buf);
+	}
+
+	if (!use_strategies) {
+		if (!remoteheads->next)
+			add_strategies(pull_twohead, DEFAULT_TWOHEAD);
+		else
+			add_strategies(pull_octopus, DEFAULT_OCTOPUS);
+	}
+
+	for (i = 0; i < use_strategies_nr; i++) {
+		if (use_strategies[i]->attr & NO_FAST_FORWARD)
+			allow_fast_forward = 0;
+		if (use_strategies[i]->attr & NO_TRIVIAL)
+			allow_trivial = 0;
+	}
+
+	if (!remoteheads->next)
+		common = get_merge_bases(lookup_commit(head),
+				remoteheads->item, 1);
+	else {
+		struct commit_list *list = remoteheads;
+		commit_list_insert(lookup_commit(head), &list);
+		common = get_octopus_merge_bases(list);
+		free(list);
+	}
+
+	update_ref("updating ORIG_HEAD", "ORIG_HEAD", head, NULL, 0,
+		DIE_ON_ERR);
+
+	if (!common)
+		; /* No common ancestors found. We need a real merge. */
+	else if (!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;
+	} else if (allow_fast_forward && !remoteheads->next &&
+			!common->next &&
+			!hashcmp(common->item->object.sha1, head)) {
+		/* Again the most common case of merging one remote. */
+		struct strbuf msg;
+		struct object *o;
+		char hex[41];
+
+		strcpy(hex, find_unique_abbrev(head, DEFAULT_ABBREV));
+
+		printf("Updating %s..%s\n",
+			hex,
+			find_unique_abbrev(remoteheads->item->object.sha1,
+			DEFAULT_ABBREV));
+		refresh_cache(REFRESH_QUIET);
+		strbuf_init(&msg, 0);
+		strbuf_addstr(&msg, "Fast forward");
+		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;
+
+		if (checkout_fast_forward(head, remoteheads->item->object.sha1))
+			return 1;
+
+		finish(o->sha1, msg.buf);
+		drop_save();
+		return 0;
+	} else if (!remoteheads->next && common->next)
+		;
+		/*
+		 * We are not doing octopus and not fast forward.  Need
+		 * a real merge.
+		 */
+	else if (!remoteheads->next && !common->next && option_commit) {
+		/*
+		 * We are not doing octopus, not fast forward, and have
+		 * only one common.
+		 */
+		refresh_cache(REFRESH_QUIET);
+		if (allow_trivial) {
+			/* See if it is really trivial. */
+			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();
+			printf("Nope.\n");
+		}
+	} else {
+		/*
+		 * An octopus.  If we can reach all the remote we are up
+		 * to date.
+		 */
+		int up_to_date = 1;
+		struct commit_list *j;
+
+		for (j = remoteheads; j; j = j->next) {
+			struct commit_list *common_one;
+
+			/*
+			 * Here we *have* to calculate the individual
+			 * merge_bases again, otherwise "git merge HEAD^
+			 * HEAD^^" would be missed.
+			 */
+			common_one = get_merge_bases(lookup_commit(head),
+				j->item, 1);
+			if (hashcmp(common_one->item->object.sha1,
+				j->item->object.sha1)) {
+				up_to_date = 0;
+				break;
+			}
+		}
+		if (up_to_date) {
+			finish_up_to_date("Already up-to-date. Yeeah!");
+			return 0;
+		}
+	}
+
+	/* We are going to make a new commit. */
+	git_committer_info(IDENT_ERROR_ON_NO_NAME);
+
+	/*
+	 * At this point, we need a real merge.  No matter what strategy
+	 * we use, it would operate on the index, possibly affecting the
+	 * working tree, and when resolved cleanly, have the desired
+	 * tree in the index -- this means that the index must be in
+	 * 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);
+	}
+
+	for (i = 0; i < use_strategies_nr; i++) {
+		int ret;
+		if (i) {
+			printf("Rewinding the tree to pristine...\n");
+			restore_state();
+		}
+		if (use_strategies_nr != 1)
+			printf("Trying merge strategy %s...\n",
+				use_strategies[i]->name);
+		/*
+		 * Remember which strategy left the state in the working
+		 * tree.
+		 */
+		wt_strategy = use_strategies[i]->name;
+
+		ret = try_merge_strategy(use_strategies[i]->name,
+			common, head_arg);
+		if (!option_commit && !ret) {
+			merge_was_ok = 1;
+			/*
+			 * This is necessary here just to avoid writing
+			 * the tree, but later we will *not* exit with
+			 * status code 1 because merge_was_ok is set.
+			 */
+			ret = 1;
+		}
+
+		if (ret) {
+			/*
+			 * The backend exits with 1 when conflicts are
+			 * left to be resolved, with 2 when it does not
+			 * handle the given merge at all.
+			 */
+			if (ret == 1) {
+				int cnt = evaluate_result();
+
+				if (best_cnt <= 0 || cnt <= best_cnt) {
+					best_strategy = use_strategies[i]->name;
+					best_cnt = cnt;
+				}
+			}
+			if (merge_was_ok)
+				break;
+			else
+				continue;
+		}
+
+		/* Automerge succeeded. */
+		write_tree_trivial(result_tree);
+		automerge_was_ok = 1;
+		break;
+	}
+
+	/*
+	 * 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);
+
+	/*
+	 * Pick the result from the best strategy and have the user fix
+	 * it up.
+	 */
+	if (!best_strategy) {
+		restore_state();
+		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;
+	} 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();
+		printf("Using the %s to prepare resolving by hand.\n",
+			best_strategy);
+		try_merge_strategy(best_strategy, common, 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("Could open %s for writing",
+				git_path("MERGE_HEAD"));
+		if (write_in_full(fd, buf.buf, buf.len) != buf.len)
+			die("Could not write to %s", git_path("MERGE_HEAD"));
+		close(fd);
+		strbuf_addch(&merge_msg, '\n');
+		fd = open(git_path("MERGE_MSG"), O_WRONLY | O_CREAT, 0666);
+		if (fd < 0)
+			die("Could open %s for writing", git_path("MERGE_MSG"));
+		if (write_in_full(fd, merge_msg.buf, merge_msg.len) !=
+			merge_msg.len)
+			die("Could not write to %s", git_path("MERGE_MSG"));
+		close(fd);
+	}
+
+	if (merge_was_ok) {
+		fprintf(stderr, "Automatic merge went well; "
+			"stopped before committing as requested\n");
+		return 0;
+	} else
+		return suggest_conflicts();
+}
diff --git a/builtin-read-tree.c b/builtin-read-tree.c
index 5a09e17f1ad4fe..72a6de302f8872 100644
--- a/builtin-read-tree.c
+++ b/builtin-read-tree.c
@@ -29,30 +29,6 @@ static int list_tree(unsigned char *sha1)
 	return 0;
 }
 
-static int read_cache_unmerged(void)
-{
-	int i;
-	struct cache_entry **dst;
-	struct cache_entry *last = NULL;
-
-	read_cache();
-	dst = active_cache;
-	for (i = 0; i < active_nr; i++) {
-		struct cache_entry *ce = active_cache[i];
-		if (ce_stage(ce)) {
-			remove_name_hash(ce);
-			if (last && !strcmp(ce->name, last->name))
-				continue;
-			cache_tree_invalidate_path(active_cache_tree, ce->name);
-			last = ce;
-			continue;
-		}
-		*dst++ = ce;
-	}
-	active_nr = dst - active_cache;
-	return !!last;
-}
-
 static void prime_cache_tree_rec(struct cache_tree *it, struct tree *tree)
 {
 	struct tree_desc desc;
diff --git a/builtin-remote.c b/builtin-remote.c
index 145dd8568c7a64..1491354a9d5d22 100644
--- a/builtin-remote.c
+++ b/builtin-remote.c
@@ -29,12 +29,6 @@ static inline int postfixcmp(const char *string, const char *postfix)
 	return strcmp(string + len1 - len2, postfix);
 }
 
-static inline const char *skip_prefix(const char *name, const char *prefix)
-{
-	return !name ? "" :
-		prefixcmp(name, prefix) ?  name : name + strlen(prefix);
-}
-
 static int opt_parse_track(const struct option *opt, const char *arg, int not)
 {
 	struct path_list *list = opt->value;
@@ -182,12 +176,18 @@ static int config_read_branches(const char *key, const char *value, void *cb)
 			info->remote = xstrdup(value);
 		} else {
 			char *space = strchr(value, ' ');
-			value = skip_prefix(value, "refs/heads/");
+			const char *ptr = skip_prefix(value, "refs/heads/");
+			if (ptr)
+				value = ptr;
 			while (space) {
 				char *merge;
 				merge = xstrndup(value, space - value);
 				path_list_append(merge, &info->merge);
-				value = skip_prefix(space + 1, "refs/heads/");
+				ptr = skip_prefix(space + 1, "refs/heads/");
+				if (ptr)
+					value = ptr;
+				else
+					value = space + 1;
 				space = strchr(value, ' ');
 			}
 			path_list_append(xstrdup(value), &info->merge);
@@ -219,7 +219,12 @@ static int handle_one_branch(const char *refname,
 	refspec.dst = (char *)refname;
 	if (!remote_find_tracking(states->remote, &refspec)) {
 		struct path_list_item *item;
-		const char *name = skip_prefix(refspec.src, "refs/heads/");
+		const char *name, *ptr;
+		ptr = skip_prefix(refspec.src, "refs/heads/");
+		if (ptr)
+			name = ptr;
+		else
+			name = refspec.src;
 		/* symbolic refs pointing nowhere were handled already */
 		if ((flags & REF_ISSYMREF) ||
 				unsorted_path_list_has_path(&states->tracked,
@@ -248,6 +253,7 @@ static int get_ref_states(const struct ref *ref, struct ref_states *states)
 		struct path_list *target = &states->tracked;
 		unsigned char sha1[20];
 		void *util = NULL;
+		const char *ptr;
 
 		if (!ref->peer_ref || read_ref(ref->peer_ref->name, sha1))
 			target = &states->new;
@@ -256,8 +262,10 @@ static int get_ref_states(const struct ref *ref, struct ref_states *states)
 			if (hashcmp(sha1, ref->new_sha1))
 				util = &states;
 		}
-		path_list_append(skip_prefix(ref->name, "refs/heads/"),
-				target)->util = util;
+		ptr = skip_prefix(ref->name, "refs/heads/");
+		if (!ptr)
+			ptr = ref->name;
+		path_list_append(ptr, target)->util = util;
 	}
 	free_refs(fetch_map);
 
@@ -522,10 +530,15 @@ static int show(int argc, const char **argv)
 					"es" : "");
 			for (i = 0; i < states.remote->push_refspec_nr; i++) {
 				struct refspec *spec = states.remote->push + i;
+				const char *p = "", *q = "";
+				if (spec->src)
+					p = skip_prefix(spec->src, "refs/heads/");
+				if (spec->dst)
+					q = skip_prefix(spec->dst, "refs/heads/");
 				printf(" %s%s%s%s", spec->force ? "+" : "",
-					skip_prefix(spec->src, "refs/heads/"),
+					p ? p : spec->src,
 					spec->dst ? ":" : "",
-					skip_prefix(spec->dst, "refs/heads/"));
+					q ? q : spec->dst);
 			}
 			printf("\n");
 		}
diff --git a/builtin.h b/builtin.h
index b460b2da6f4179..0e605d4f4aa748 100644
--- a/builtin.h
+++ b/builtin.h
@@ -2,6 +2,9 @@
 #define BUILTIN_H
 
 #include "git-compat-util.h"
+#include "strbuf.h"
+#include "cache.h"
+#include "commit.h"
 
 extern const char git_version_string[];
 extern const char git_usage_string[];
@@ -11,6 +14,10 @@ extern void list_common_cmds_help(void);
 extern void help_unknown_cmd(const char *cmd);
 extern void prune_packed_objects(int);
 extern int read_line_with_nul(char *buf, int size, FILE *file);
+extern int fmt_merge_msg(int merge_summary, struct strbuf *in,
+	struct strbuf *out);
+extern int commit_tree(const char *msg, unsigned char *tree,
+		struct commit_list *parents, unsigned char *ret);
 
 extern int cmd_add(int argc, const char **argv, const char *prefix);
 extern int cmd_annotate(int argc, const char **argv, const char *prefix);
@@ -57,6 +64,7 @@ extern int cmd_ls_tree(int argc, const char **argv, const char *prefix);
 extern int cmd_ls_remote(int argc, const char **argv, const char *prefix);
 extern int cmd_mailinfo(int argc, const char **argv, const char *prefix);
 extern int cmd_mailsplit(int argc, const char **argv, const char *prefix);
+extern int cmd_merge(int argc, const char **argv, const char *prefix);
 extern int cmd_merge_base(int argc, const char **argv, const char *prefix);
 extern int cmd_merge_ours(int argc, const char **argv, const char *prefix);
 extern int cmd_merge_file(int argc, const char **argv, const char *prefix);
diff --git a/cache.h b/cache.h
index a8254e2f9e076b..a779d9207c8ea4 100644
--- a/cache.h
+++ b/cache.h
@@ -254,6 +254,7 @@ static inline void remove_name_hash(struct cache_entry *ce)
 
 #define read_cache() read_index(&the_index)
 #define read_cache_from(path) read_index_from(&the_index, (path))
+#define read_cache_unmerged() read_index_unmerged(&the_index)
 #define write_cache(newfd, cache, entries) write_index(&the_index, (newfd))
 #define discard_cache() discard_index(&the_index)
 #define unmerged_cache() unmerged_index(&the_index)
@@ -356,6 +357,7 @@ extern int init_db(const char *template_dir, unsigned int flags);
 /* Initialize and use the cache information */
 extern int read_index(struct index_state *);
 extern int read_index_from(struct index_state *, const char *path);
+extern int read_index_unmerged(struct index_state *);
 extern int write_index(const struct index_state *, int newfd);
 extern int discard_index(struct index_state *);
 extern int unmerged_index(const struct index_state *);
@@ -837,5 +839,6 @@ int report_path_error(const char *ps_matched, const char **pathspec, int prefix_
 void overlay_tree_on_cache(const char *tree_name, const char *prefix);
 
 char *alias_lookup(const char *alias);
+int split_cmdline(char *cmdline, const char ***argv);
 
 #endif /* CACHE_H */
diff --git a/commit.c b/commit.c
index e2d8624d9c19ad..5148ec552708bb 100644
--- a/commit.c
+++ b/commit.c
@@ -325,6 +325,14 @@ struct commit_list *commit_list_insert(struct commit *item, struct commit_list *
 	return new_list;
 }
 
+unsigned commit_list_count(const struct commit_list *l)
+{
+	unsigned c = 0;
+	for (; l; l = l->next )
+		c++;
+	return c;
+}
+
 void free_commit_list(struct commit_list *list)
 {
 	while (list) {
@@ -525,26 +533,34 @@ static struct commit *interesting(struct commit_list *list)
 	return NULL;
 }
 
-static struct commit_list *merge_bases(struct commit *one, struct commit *two)
+static struct commit_list *merge_bases_many(struct commit *one, int n, struct commit **twos)
 {
 	struct commit_list *list = NULL;
 	struct commit_list *result = NULL;
+	int i;
 
-	if (one == two)
-		/* We do not mark this even with RESULT so we do not
-		 * have to clean it up.
-		 */
-		return commit_list_insert(one, &result);
+	for (i = 0; i < n; i++) {
+		if (one == twos[i])
+			/*
+			 * We do not mark this even with RESULT so we do not
+			 * have to clean it up.
+			 */
+			return commit_list_insert(one, &result);
+	}
 
 	if (parse_commit(one))
 		return NULL;
-	if (parse_commit(two))
-		return NULL;
+	for (i = 0; i < n; i++) {
+		if (parse_commit(twos[i]))
+			return NULL;
+	}
 
 	one->object.flags |= PARENT1;
-	two->object.flags |= PARENT2;
 	insert_by_date(one, &list);
-	insert_by_date(two, &list);
+	for (i = 0; i < n; i++) {
+		twos[i]->object.flags |= PARENT2;
+		insert_by_date(twos[i], &list);
+	}
 
 	while (interesting(list)) {
 		struct commit *commit;
@@ -592,21 +608,53 @@ static struct commit_list *merge_bases(struct commit *one, struct commit *two)
 	return result;
 }
 
-struct commit_list *get_merge_bases(struct commit *one,
-					struct commit *two, int cleanup)
+struct commit_list *get_octopus_merge_bases(struct commit_list *in)
+{
+	struct commit_list *i, *j, *k, *ret = NULL;
+	struct commit_list **pptr = &ret;
+
+	for (i = in; i; i = i->next) {
+		if (!ret)
+			pptr = &commit_list_insert(i->item, pptr)->next;
+		else {
+			struct commit_list *new = NULL, *end = NULL;
+
+			for (j = ret; j; j = j->next) {
+				struct commit_list *bases;
+				bases = get_merge_bases(i->item, j->item, 1);
+				if (!new)
+					new = bases;
+				else
+					end->next = bases;
+				for (k = bases; k; k = k->next)
+					end = k;
+			}
+			ret = new;
+		}
+	}
+	return ret;
+}
+
+struct commit_list *get_merge_bases_many(struct commit *one,
+					 int n,
+					 struct commit **twos,
+					 int cleanup)
 {
 	struct commit_list *list;
 	struct commit **rslt;
 	struct commit_list *result;
 	int cnt, i, j;
 
-	result = merge_bases(one, two);
-	if (one == two)
-		return result;
+	result = merge_bases_many(one, n, twos);
+	for (i = 0; i < n; i++) {
+		if (one == twos[i])
+			return result;
+	}
 	if (!result || !result->next) {
 		if (cleanup) {
 			clear_commit_marks(one, all_flags);
-			clear_commit_marks(two, all_flags);
+			for (i = 0; i < n; i++)
+				clear_commit_marks(twos[i], all_flags);
 		}
 		return result;
 	}
@@ -624,12 +672,13 @@ struct commit_list *get_merge_bases(struct commit *one,
 	free_commit_list(result);
 
 	clear_commit_marks(one, all_flags);
-	clear_commit_marks(two, all_flags);
+	for (i = 0; i < n; i++)
+		clear_commit_marks(twos[i], all_flags);
 	for (i = 0; i < cnt - 1; i++) {
 		for (j = i+1; j < cnt; j++) {
 			if (!rslt[i] || !rslt[j])
 				continue;
-			result = merge_bases(rslt[i], rslt[j]);
+			result = merge_bases_many(rslt[i], 1, &rslt[j]);
 			clear_commit_marks(rslt[i], all_flags);
 			clear_commit_marks(rslt[j], all_flags);
 			for (list = result; list; list = list->next) {
@@ -651,6 +700,12 @@ struct commit_list *get_merge_bases(struct commit *one,
 	return result;
 }
 
+struct commit_list *get_merge_bases(struct commit *one, struct commit *two,
+				    int cleanup)
+{
+	return get_merge_bases_many(one, 1, &two, cleanup);
+}
+
 int in_merge_bases(struct commit *commit, struct commit **reference, int num)
 {
 	struct commit_list *bases, *b;
@@ -670,3 +725,55 @@ int in_merge_bases(struct commit *commit, struct commit **reference, int num)
 	free_commit_list(bases);
 	return ret;
 }
+
+struct commit_list *reduce_heads(struct commit_list *heads)
+{
+	struct commit_list *p;
+	struct commit_list *result = NULL, **tail = &result;
+	struct commit **other;
+	size_t num_head, num_other;
+
+	if (!heads)
+		return NULL;
+
+	/* Avoid unnecessary reallocations */
+	for (p = heads, num_head = 0; p; p = p->next)
+		num_head++;
+	other = xcalloc(sizeof(*other), num_head);
+
+	/* For each commit, see if it can be reached by others */
+	for (p = heads; p; p = p->next) {
+		struct commit_list *q, *base;
+
+		/* Do we already have this in the result? */
+		for (q = result; q; q = q->next)
+			if (p->item == q->item)
+				break;
+		if (q)
+			continue;
+
+		num_other = 0;
+		for (q = heads; q; q = q->next) {
+			if (p->item == q->item)
+				continue;
+			other[num_other++] = q->item;
+		}
+		if (num_other)
+			base = get_merge_bases_many(p->item, num_other, other, 1);
+		else
+			base = NULL;
+		/*
+		 * If p->item does not have anything common with other
+		 * commits, there won't be any merge base.  If it is
+		 * reachable from some of the others, p->item will be
+		 * the merge base.  If its history is connected with
+		 * others, but p->item is not reachable by others, we
+		 * will get something other than p->item back.
+		 */
+		if (!base || (base->item != p->item))
+			tail = &(commit_list_insert(p->item, tail)->next);
+		free_commit_list(base);
+	}
+	free(other);
+	return result;
+}
diff --git a/commit.h b/commit.h
index fda7ad03c0b1d0..77de9621d9c926 100644
--- a/commit.h
+++ b/commit.h
@@ -41,6 +41,7 @@ int parse_commit_buffer(struct commit *item, void *buffer, unsigned long size);
 int parse_commit(struct commit *item);
 
 struct commit_list * commit_list_insert(struct commit *item, struct commit_list **list_p);
+unsigned commit_list_count(const struct commit_list *l);
 struct commit_list * insert_by_date(struct commit *item, struct commit_list **list);
 
 void free_commit_list(struct commit_list *list);
@@ -120,6 +121,7 @@ int read_graft_file(const char *graft_file);
 struct commit_graft *lookup_commit_graft(const unsigned char *sha1);
 
 extern struct commit_list *get_merge_bases(struct commit *rev1, struct commit *rev2, int cleanup);
+extern struct commit_list *get_octopus_merge_bases(struct commit_list *in);
 
 extern int register_shallow(const unsigned char *sha1);
 extern int unregister_shallow(const unsigned char *sha1);
@@ -137,4 +139,6 @@ static inline int single_parent(struct commit *commit)
 	return commit->parents && !commit->parents->next;
 }
 
+struct commit_list *reduce_heads(struct commit_list *heads);
+
 #endif /* COMMIT_H */
diff --git a/git-merge.sh b/contrib/examples/git-merge.sh
similarity index 100%
rename from git-merge.sh
rename to contrib/examples/git-merge.sh
diff --git a/git-compat-util.h b/git-compat-util.h
index 8c7e11473390c1..cf89cdf4598b37 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -157,6 +157,12 @@ extern void set_warn_routine(void (*routine)(const char *warn, va_list params));
 extern int prefixcmp(const char *str, const char *prefix);
 extern time_t tm_to_time_t(const struct tm *tm);
 
+static inline const char *skip_prefix(const char *str, const char *prefix)
+{
+	size_t len = strlen(prefix);
+	return strncmp(str, prefix, len) ? NULL : str + len;
+}
+
 #ifdef NO_MMAP
 
 #ifndef PROT_READ
diff --git a/git.c b/git.c
index 7075533aa7243a..74ea0e6cc52f62 100644
--- a/git.c
+++ b/git.c
@@ -127,59 +127,6 @@ static int handle_options(const char*** argv, int* argc, int* envchanged)
 	return handled;
 }
 
-static int split_cmdline(char *cmdline, const char ***argv)
-{
-	int src, dst, count = 0, size = 16;
-	char quoted = 0;
-
-	*argv = xmalloc(sizeof(char*) * size);
-
-	/* split alias_string */
-	(*argv)[count++] = cmdline;
-	for (src = dst = 0; cmdline[src];) {
-		char c = cmdline[src];
-		if (!quoted && isspace(c)) {
-			cmdline[dst++] = 0;
-			while (cmdline[++src]
-					&& isspace(cmdline[src]))
-				; /* skip */
-			if (count >= size) {
-				size += 16;
-				*argv = xrealloc(*argv, sizeof(char*) * size);
-			}
-			(*argv)[count++] = cmdline + dst;
-		} else if(!quoted && (c == '\'' || c == '"')) {
-			quoted = c;
-			src++;
-		} else if (c == quoted) {
-			quoted = 0;
-			src++;
-		} else {
-			if (c == '\\' && quoted != '\'') {
-				src++;
-				c = cmdline[src];
-				if (!c) {
-					free(*argv);
-					*argv = NULL;
-					return error("cmdline ends with \\");
-				}
-			}
-			cmdline[dst++] = c;
-			src++;
-		}
-	}
-
-	cmdline[dst] = 0;
-
-	if (quoted) {
-		free(*argv);
-		*argv = NULL;
-		return error("unclosed quote");
-	}
-
-	return count;
-}
-
 static int handle_alias(int *argcp, const char ***argv)
 {
 	int envchanged = 0, ret = 0, saved_errno = errno;
@@ -366,6 +313,7 @@ static void handle_internal_command(int argc, const char **argv)
 		{ "ls-remote", cmd_ls_remote },
 		{ "mailinfo", cmd_mailinfo },
 		{ "mailsplit", cmd_mailsplit },
+		{ "merge", cmd_merge, RUN_SETUP | NEED_WORK_TREE },
 		{ "merge-base", cmd_merge_base, RUN_SETUP },
 		{ "merge-file", cmd_merge_file },
 		{ "merge-ours", cmd_merge_ours, RUN_SETUP },
diff --git a/parse-options.c b/parse-options.c
index ae88885d4da573..2fd5edbf53546a 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -5,12 +5,6 @@
 #define OPT_SHORT 1
 #define OPT_UNSET 2
 
-static inline const char *skip_prefix(const char *str, const char *prefix)
-{
-	size_t len = strlen(prefix);
-	return strncmp(str, prefix, len) ? NULL : str + len;
-}
-
 static int opterror(const struct option *opt, const char *reason, int flags)
 {
 	if (flags & OPT_SHORT)
diff --git a/read-cache.c b/read-cache.c
index f83de8c4158e08..d801f9d1cf9eca 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -1410,3 +1410,34 @@ int write_index(const struct index_state *istate, int newfd)
 	}
 	return ce_flush(&c, newfd);
 }
+
+/*
+ * Read the index file that is potentially unmerged into given
+ * index_state, dropping any unmerged entries.  Returns true is
+ * the index is unmerged.  Callers who want to refuse to work
+ * from an unmerged state can call this and check its return value,
+ * instead of calling read_cache().
+ */
+int read_index_unmerged(struct index_state *istate)
+{
+	int i;
+	struct cache_entry **dst;
+	struct cache_entry *last = NULL;
+
+	read_index(istate);
+	dst = istate->cache;
+	for (i = 0; i < istate->cache_nr; i++) {
+		struct cache_entry *ce = istate->cache[i];
+		if (ce_stage(ce)) {
+			remove_name_hash(ce);
+			if (last && !strcmp(ce->name, last->name))
+				continue;
+			cache_tree_invalidate_path(istate->cache_tree, ce->name);
+			last = ce;
+			continue;
+		}
+		*dst++ = ce;
+	}
+	istate->cache_nr = dst - istate->cache;
+	return !!last;
+}
diff --git a/t/t6021-merge-criss-cross.sh b/t/t6021-merge-criss-cross.sh
index 0ab14a6e81302d..331b9b07d4eedb 100755
--- a/t/t6021-merge-criss-cross.sh
+++ b/t/t6021-merge-criss-cross.sh
@@ -89,4 +89,8 @@ EOF
 
 test_expect_success 'Criss-cross merge result' 'cmp file file-expect'
 
+test_expect_success 'Criss-cross merge fails (-s resolve)' \
+'git reset --hard A^ &&
+test_must_fail git merge -s resolve -m "final merge" B'
+
 test_done
diff --git a/t/t7600-merge.sh b/t/t7600-merge.sh
index d21cd290d3d8e3..d4cf6289a4c06e 100755
--- a/t/t7600-merge.sh
+++ b/t/t7600-merge.sh
@@ -465,11 +465,51 @@ test_expect_success 'merge log message' '
 	git merge --no-log c2 &&
 	git show -s --pretty=format:%b HEAD >msg.act &&
 	verify_diff msg.nolog msg.act "[OOPS] bad merge log message" &&
+
 	git merge --log c3 &&
 	git show -s --pretty=format:%b HEAD >msg.act &&
+	verify_diff msg.log msg.act "[OOPS] bad merge log message" &&
+
+	git reset --hard HEAD^ &&
+	git config merge.log yes &&
+	git merge c3 &&
+	git show -s --pretty=format:%b HEAD >msg.act &&
 	verify_diff msg.log msg.act "[OOPS] bad merge log message"
 '
 
 test_debug 'gitk --all'
 
+test_expect_success 'merge c1 with c0, c2, c0, and c1' '
+       git reset --hard c1 &&
+       git config branch.master.mergeoptions "" &&
+       test_tick &&
+       git merge c0 c2 c0 c1 &&
+       verify_merge file result.1-5 &&
+       verify_parents $c1 $c2
+'
+
+test_debug 'gitk --all'
+
+test_expect_success 'merge c1 with c0, c2, c0, and c1' '
+       git reset --hard c1 &&
+       git config branch.master.mergeoptions "" &&
+       test_tick &&
+       git merge c0 c2 c0 c1 &&
+       verify_merge file result.1-5 &&
+       verify_parents $c1 $c2
+'
+
+test_debug 'gitk --all'
+
+test_expect_success 'merge c1 with c1 and c2' '
+       git reset --hard c1 &&
+       git config branch.master.mergeoptions "" &&
+       test_tick &&
+       git merge c1 c2 &&
+       verify_merge file result.1-5 &&
+       verify_parents $c1 $c2
+'
+
+test_debug 'gitk --all'
+
 test_done
diff --git a/t/t7601-merge-pull-config.sh b/t/t7601-merge-pull-config.sh
new file mode 100755
index 00000000000000..95b4d71c5154a6
--- /dev/null
+++ b/t/t7601-merge-pull-config.sh
@@ -0,0 +1,129 @@
+#!/bin/sh
+
+test_description='git-merge
+
+Testing pull.* configuration parsing.'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	echo c0 >c0.c &&
+	git add c0.c &&
+	git commit -m c0 &&
+	git tag c0 &&
+	echo c1 >c1.c &&
+	git add c1.c &&
+	git commit -m c1 &&
+	git tag c1 &&
+	git reset --hard c0 &&
+	echo c2 >c2.c &&
+	git add c2.c &&
+	git commit -m c2 &&
+	git tag c2 &&
+	git reset --hard c0 &&
+	echo c3 >c3.c &&
+	git add c3.c &&
+	git commit -m c3 &&
+	git tag c3
+'
+
+test_expect_success 'merge c1 with c2' '
+	git reset --hard c1 &&
+	test -f c0.c &&
+	test -f c1.c &&
+	test ! -f c2.c &&
+	test ! -f c3.c &&
+	git merge c2 &&
+	test -f c1.c &&
+	test -f c2.c
+'
+
+test_expect_success 'merge c1 with c2 (ours in pull.twohead)' '
+	git reset --hard c1 &&
+	git config pull.twohead ours &&
+	git merge c2 &&
+	test -f c1.c &&
+	! test -f c2.c
+'
+
+test_expect_success 'merge c1 with c2 and c3 (recursive in pull.octopus)' '
+	git reset --hard c1 &&
+	git config pull.octopus "recursive" &&
+	test_must_fail git merge c2 c3 &&
+	test "$(git rev-parse c1)" = "$(git rev-parse HEAD)"
+'
+
+test_expect_success 'merge c1 with c2 and c3 (recursive and octopus in pull.octopus)' '
+	git reset --hard c1 &&
+	git config pull.octopus "recursive octopus" &&
+	git merge c2 c3 &&
+	test "$(git rev-parse c1)" != "$(git rev-parse HEAD)" &&
+	test "$(git rev-parse c1)" = "$(git rev-parse HEAD^1)" &&
+	test "$(git rev-parse c2)" = "$(git rev-parse HEAD^2)" &&
+	test "$(git rev-parse c3)" = "$(git rev-parse HEAD^3)" &&
+	git diff --exit-code &&
+	test -f c0.c &&
+	test -f c1.c &&
+	test -f c2.c &&
+	test -f c3.c
+'
+
+conflict_count()
+{
+	{
+		git diff-files --name-only
+		git ls-files --unmerged
+	} | wc -l
+}
+
+# c4 - c5
+#    \ c6
+#
+# There are two conflicts here:
+#
+# 1) Because foo.c is renamed to bar.c, recursive will handle this,
+# resolve won't.
+#
+# 2) One in conflict.c and that will always fail.
+
+test_expect_success 'setup conflicted merge' '
+	git reset --hard c0 &&
+	echo A >conflict.c &&
+	git add conflict.c &&
+	echo contents >foo.c &&
+	git add foo.c &&
+	git commit -m c4 &&
+	git tag c4 &&
+	echo B >conflict.c &&
+	git add conflict.c &&
+	git mv foo.c bar.c &&
+	git commit -m c5 &&
+	git tag c5 &&
+	git reset --hard c4 &&
+	echo C >conflict.c &&
+	git add conflict.c &&
+	echo secondline >> foo.c &&
+	git add foo.c &&
+	git commit -m c6 &&
+	git tag c6
+'
+
+# First do the merge with resolve and recursive then verify that
+# recusive is choosen.
+
+test_expect_success 'merge picks up the best result' '
+	git config pull.twohead "recursive resolve" &&
+	git reset --hard c5 &&
+	git merge -s resolve c6
+	resolve_count=$(conflict_count) &&
+	git reset --hard c5 &&
+	git merge -s recursive c6
+	recursive_count=$(conflict_count) &&
+	git reset --hard c5 &&
+	git merge c6
+	auto_count=$(conflict_count) &&
+	test $auto_count = $recursive_count &&
+	test $auto_count != $resolve_count
+'
+
+test_done
diff --git a/t/t7602-merge-octopus-many.sh b/t/t7602-merge-octopus-many.sh
new file mode 100755
index 00000000000000..fcb8285746420e
--- /dev/null
+++ b/t/t7602-merge-octopus-many.sh
@@ -0,0 +1,52 @@
+#!/bin/sh
+
+test_description='git-merge
+
+Testing octopus merge with more than 25 refs.'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	echo c0 > c0.c &&
+	git add c0.c &&
+	git commit -m c0 &&
+	git tag c0 &&
+	i=1 &&
+	while test $i -le 30
+	do
+		git reset --hard c0 &&
+		echo c$i > c$i.c &&
+		git add c$i.c &&
+		git commit -m c$i &&
+		git tag c$i &&
+		i=`expr $i + 1` || return 1
+	done
+'
+
+test_expect_success 'merge c1 with c2, c3, c4, ... c29' '
+	git reset --hard c1 &&
+	i=2 &&
+	refs="" &&
+	while test $i -le 30
+	do
+		refs="$refs c$i"
+		i=`expr $i + 1`
+	done
+	git merge $refs &&
+	test "$(git rev-parse c1)" != "$(git rev-parse HEAD)" &&
+	i=1 &&
+	while test $i -le 30
+	do
+		test "$(git rev-parse c$i)" = "$(git rev-parse HEAD^$i)" &&
+		i=`expr $i + 1` || return 1
+	done &&
+	git diff --exit-code &&
+	i=1 &&
+	while test $i -le 30
+	do
+		test -f c$i.c &&
+		i=`expr $i + 1` || return 1
+	done
+'
+
+test_done
diff --git a/t/t7603-merge-reduce-heads.sh b/t/t7603-merge-reduce-heads.sh
new file mode 100755
index 00000000000000..17b19dc11f2b1a
--- /dev/null
+++ b/t/t7603-merge-reduce-heads.sh
@@ -0,0 +1,63 @@
+#!/bin/sh
+
+test_description='git-merge
+
+Testing octopus merge when reducing parents to independent branches.'
+
+. ./test-lib.sh
+
+# 0 - 1
+#   \ 2
+#   \ 3
+#   \ 4 - 5
+#
+# So 1, 2, 3 and 5 should be kept, 4 should be avoided.
+
+test_expect_success 'setup' '
+	echo c0 > c0.c &&
+	git add c0.c &&
+	git commit -m c0 &&
+	git tag c0 &&
+	echo c1 > c1.c &&
+	git add c1.c &&
+	git commit -m c1 &&
+	git tag c1 &&
+	git reset --hard c0 &&
+	echo c2 > c2.c &&
+	git add c2.c &&
+	git commit -m c2 &&
+	git tag c2 &&
+	git reset --hard c0 &&
+	echo c3 > c3.c &&
+	git add c3.c &&
+	git commit -m c3 &&
+	git tag c3 &&
+	git reset --hard c0 &&
+	echo c4 > c4.c &&
+	git add c4.c &&
+	git commit -m c4 &&
+	git tag c4 &&
+	echo c5 > c5.c &&
+	git add c5.c &&
+	git commit -m c5 &&
+	git tag c5
+'
+
+test_expect_success 'merge c1 with c2, c3, c4, c5' '
+	git reset --hard c1 &&
+	git merge c2 c3 c4 c5 &&
+	test "$(git rev-parse c1)" != "$(git rev-parse HEAD)" &&
+	test "$(git rev-parse c1)" = "$(git rev-parse HEAD^1)" &&
+	test "$(git rev-parse c2)" = "$(git rev-parse HEAD^2)" &&
+	test "$(git rev-parse c3)" = "$(git rev-parse HEAD^3)" &&
+	test "$(git rev-parse c5)" = "$(git rev-parse HEAD^4)" &&
+	git diff --exit-code &&
+	test -f c0.c &&
+	test -f c1.c &&
+	test -f c2.c &&
+	test -f c3.c &&
+	test -f c4.c &&
+	test -f c5.c
+'
+
+test_done
diff --git a/t/t7604-merge-custom-message.sh b/t/t7604-merge-custom-message.sh
new file mode 100755
index 00000000000000..6081677d234f1f
--- /dev/null
+++ b/t/t7604-merge-custom-message.sh
@@ -0,0 +1,37 @@
+#!/bin/sh
+
+test_description='git-merge
+
+Testing merge when using a custom message for the merge commit.'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	echo c0 > c0.c &&
+	git add c0.c &&
+	git commit -m c0 &&
+	git tag c0 &&
+	echo c1 > c1.c &&
+	git add c1.c &&
+	git commit -m c1 &&
+	git tag c1 &&
+	git reset --hard c0 &&
+	echo c2 > c2.c &&
+	git add c2.c &&
+	git commit -m c2 &&
+	git tag c2
+'
+
+cat >expected <<\EOF
+custom message
+
+Merge commit 'c2'
+EOF
+test_expect_success 'merge c2 with a custom message' '
+	git reset --hard c1 &&
+	git merge -m "custom message" c2 &&
+	git cat-file commit HEAD | sed -e "1,/^$/d" > actual &&
+	test_cmp expected actual
+'
+
+test_done
diff --git a/t/t7605-merge-resolve.sh b/t/t7605-merge-resolve.sh
new file mode 100755
index 00000000000000..ee21a107fd99e3
--- /dev/null
+++ b/t/t7605-merge-resolve.sh
@@ -0,0 +1,46 @@
+#!/bin/sh
+
+test_description='git-merge
+
+Testing the resolve strategy.'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	echo c0 > c0.c &&
+	git add c0.c &&
+	git commit -m c0 &&
+	git tag c0 &&
+	echo c1 > c1.c &&
+	git add c1.c &&
+	git commit -m c1 &&
+	git tag c1 &&
+	git reset --hard c0 &&
+	echo c2 > c2.c &&
+	git add c2.c &&
+	git commit -m c2 &&
+	git tag c2 &&
+	git reset --hard c0 &&
+	echo c3 > c2.c &&
+	git add c2.c &&
+	git commit -m c3 &&
+	git tag c3
+'
+
+test_expect_success 'merge c1 to c2' '
+	git reset --hard c1 &&
+	git merge -s resolve c2 &&
+	test "$(git rev-parse c1)" != "$(git rev-parse HEAD)" &&
+	test "$(git rev-parse c1)" = "$(git rev-parse HEAD^1)" &&
+	test "$(git rev-parse c2)" = "$(git rev-parse HEAD^2)" &&
+	git diff --exit-code &&
+	test -f c0.c &&
+	test -f c1.c &&
+	test -f c2.c
+'
+
+test_expect_success 'merge c2 to c3 (fails)' '
+	git reset --hard c2 &&
+	test_must_fail git merge -s resolve c3
+'
+test_done