git/builtin/merge.c

/*
 * Builtin "git merge"
 *
 * Copyright (c) 2008 Miklos Vajna <vmiklos@frugalware.org>
 *
 * Based on git-merge.sh by Junio C Hamano.
 */

#define USE_THE_INDEX_COMPATIBILITY_MACROS
#include "cache.h"
#include "config.h"
#include "parse-options.h"
#include "builtin.h"
#include "lockfile.h"
#include "run-command.h"
#include "hook.h"
#include "diff.h"
#include "diff-merges.h"
#include "refs.h"
#include "refspec.h"
#include "commit.h"
#include "diffcore.h"
#include "revision.h"
#include "unpack-trees.h"
#include "cache-tree.h"
#include "dir.h"
#include "utf8.h"
#include "log-tree.h"
#include "color.h"
#include "rerere.h"
#include "help.h"
#include "merge-recursive.h"
#include "merge-ort-wrappers.h"
#include "resolve-undo.h"
#include "remote.h"
#include "fmt-merge-msg.h"
#include "gpg-interface.h"
#include "sequencer.h"
#include "string-list.h"
#include "packfile.h"
#include "tag.h"
#include "alias.h"
#include "branch.h"
#include "commit-reach.h"
#include "wt-status.h"
#include "commit-graph.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[] = {
	N_("git merge [<options>] [<commit>...]"),
	"git merge --abort",
	"git merge --continue",
	NULL
};

static int show_diffstat = 1, shortlog_len = -1, squash;
static int option_commit = -1;
static int option_edit = -1;
static int allow_trivial = 1, have_message, verify_signatures;
static int check_trust_level = 1;
static int overwrite_ignore = 1;
static struct strbuf merge_msg = STRBUF_INIT;
static struct strategy **use_strategies;
static size_t use_strategies_nr, use_strategies_alloc;
static const char **xopts;
static size_t xopts_nr, xopts_alloc;
static const char *branch;
static char *branch_mergeoptions;
static int verbosity;
static int allow_rerere_auto;
static int abort_current_merge;
static int quit_current_merge;
static int continue_current_merge;
static int allow_unrelated_histories;
static int show_progress = -1;
static int default_to_upstream = 1;
static int signoff;
static const char *sign_commit;
static int autostash;
static int no_verify;
static char *into_name;

static struct strategy all_strategy[] = {
	{ "recursive",  NO_TRIVIAL },
	{ "octopus",    DEFAULT_OCTOPUS },
	{ "ort",        DEFAULT_TWOHEAD | NO_TRIVIAL },
	{ "resolve",    0 },
	{ "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
	{ "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
};

static const char *pull_twohead, *pull_octopus;

enum ff_type {
	FF_NO,
	FF_ALLOW,
	FF_ONLY
};

static enum ff_type fast_forward = FF_ALLOW;

static const char *cleanup_arg;
static enum commit_msg_cleanup_mode cleanup_mode;

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 if (arg) {
		strbuf_addf(buf, "%s%s", buf->len ? "\n\n" : "", arg);
		have_message = 1;
	} else
		return error(_("switch `m' requires a value"));
	return 0;
}

static enum parse_opt_result option_read_message(struct parse_opt_ctx_t *ctx,
						 const struct option *opt,
						 const char *arg_not_used,
						 int unset)
{
	struct strbuf *buf = opt->value;
	const char *arg;

	BUG_ON_OPT_ARG(arg_not_used);
	if (unset)
		BUG("-F cannot be negated");

	if (ctx->opt) {
		arg = ctx->opt;
		ctx->opt = NULL;
	} else if (ctx->argc > 1) {
		ctx->argc--;
		arg = *++ctx->argv;
	} else
		return error(_("option `%s' requires a value"), opt->long_name);

	if (buf->len)
		strbuf_addch(buf, '\n');
	if (ctx->prefix && !is_absolute_path(arg))
		arg = prefix_filename(ctx->prefix, arg);
	if (strbuf_read_file(buf, arg, 0) < 0)
		return error(_("could not read file '%s'"), arg);
	have_message = 1;

	return 0;
}

static struct strategy *get_strategy(const char *name)
{
	int i;
	struct strategy *ret;
	static struct cmdnames main_cmds, other_cmds;
	static int loaded;
	char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");

	if (!name)
		return NULL;

	if (default_strategy &&
	    !strcmp(default_strategy, "ort") &&
	    !strcmp(name, "recursive")) {
		name = "ort";
	}

	for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
		if (!strcmp(name, all_strategy[i].name))
			return &all_strategy[i];

	if (!loaded) {
		struct cmdnames not_strategies;
		loaded = 1;

		memset(&not_strategies, 0, sizeof(struct cmdnames));
		load_command_list("git-merge-", &main_cmds, &other_cmds);
		for (i = 0; i < main_cmds.cnt; i++) {
			int j, found = 0;
			struct cmdname *ent = main_cmds.names[i];
			for (j = 0; j < ARRAY_SIZE(all_strategy); j++)
				if (!strncmp(ent->name, all_strategy[j].name, ent->len)
						&& !all_strategy[j].name[ent->len])
					found = 1;
			if (!found)
				add_cmdname(&not_strategies, ent->name, ent->len);
		}
		exclude_cmds(&main_cmds, &not_strategies);
	}
	if (!is_in_cmdlist(&main_cmds, name) && !is_in_cmdlist(&other_cmds, name)) {
		fprintf(stderr, _("Could not find merge strategy '%s'.\n"), name);
		fprintf(stderr, _("Available strategies are:"));
		for (i = 0; i < main_cmds.cnt; i++)
			fprintf(stderr, " %s", main_cmds.names[i]->name);
		fprintf(stderr, ".\n");
		if (other_cmds.cnt) {
			fprintf(stderr, _("Available custom strategies are:"));
			for (i = 0; i < other_cmds.cnt; i++)
				fprintf(stderr, " %s", other_cmds.names[i]->name);
			fprintf(stderr, ".\n");
		}
		exit(1);
	}

	CALLOC_ARRAY(ret, 1);
	ret->name = xstrdup(name);
	ret->attr = NO_TRIVIAL;
	return ret;
}

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)
{
	if (unset)
		return 0;

	append_strategy(get_strategy(name));
	return 0;
}

static int option_parse_x(const struct option *opt,
			  const char *arg, int unset)
{
	if (unset)
		return 0;

	ALLOC_GROW(xopts, xopts_nr + 1, xopts_alloc);
	xopts[xopts_nr++] = xstrdup(arg);
	return 0;
}

static int option_parse_n(const struct option *opt,
			  const char *arg, int unset)
{
	BUG_ON_OPT_ARG(arg);
	show_diffstat = unset;
	return 0;
}

static struct option builtin_merge_options[] = {
	OPT_CALLBACK_F('n', NULL, NULL, NULL,
		N_("do not show a diffstat at the end of the merge"),
		PARSE_OPT_NOARG, option_parse_n),
	OPT_BOOL(0, "stat", &show_diffstat,
		N_("show a diffstat at the end of the merge")),
	OPT_BOOL(0, "summary", &show_diffstat, N_("(synonym to --stat)")),
	{ OPTION_INTEGER, 0, "log", &shortlog_len, N_("n"),
	  N_("add (at most <n>) entries from shortlog to merge commit message"),
	  PARSE_OPT_OPTARG, NULL, DEFAULT_MERGE_LOG_LEN },
	OPT_BOOL(0, "squash", &squash,
		N_("create a single commit instead of doing a merge")),
	OPT_BOOL(0, "commit", &option_commit,
		N_("perform a commit if the merge succeeds (default)")),
	OPT_BOOL('e', "edit", &option_edit,
		N_("edit message before committing")),
	OPT_CLEANUP(&cleanup_arg),
	OPT_SET_INT(0, "ff", &fast_forward, N_("allow fast-forward (default)"), FF_ALLOW),
	OPT_SET_INT_F(0, "ff-only", &fast_forward,
		      N_("abort if fast-forward is not possible"),
		      FF_ONLY, PARSE_OPT_NONEG),
	OPT_RERERE_AUTOUPDATE(&allow_rerere_auto),
	OPT_BOOL(0, "verify-signatures", &verify_signatures,
		N_("verify that the named commit has a valid GPG signature")),
	OPT_CALLBACK('s', "strategy", &use_strategies, N_("strategy"),
		N_("merge strategy to use"), option_parse_strategy),
	OPT_CALLBACK('X', "strategy-option", &xopts, N_("option=value"),
		N_("option for selected merge strategy"), option_parse_x),
	OPT_CALLBACK('m', "message", &merge_msg, N_("message"),
		N_("merge commit message (for a non-fast-forward merge)"),
		option_parse_message),
	{ OPTION_LOWLEVEL_CALLBACK, 'F', "file", &merge_msg, N_("path"),
		N_("read message from file"), PARSE_OPT_NONEG,
		NULL, 0, option_read_message },
	OPT_STRING(0, "into-name", &into_name, N_("name"),
		   N_("use <name> instead of the real target")),
	OPT__VERBOSITY(&verbosity),
	OPT_BOOL(0, "abort", &abort_current_merge,
		N_("abort the current in-progress merge")),
	OPT_BOOL(0, "quit", &quit_current_merge,
		N_("--abort but leave index and working tree alone")),
	OPT_BOOL(0, "continue", &continue_current_merge,
		N_("continue the current in-progress merge")),
	OPT_BOOL(0, "allow-unrelated-histories", &allow_unrelated_histories,
		 N_("allow merging unrelated histories")),
	OPT_SET_INT(0, "progress", &show_progress, N_("force progress reporting"), 1),
	{ OPTION_STRING, 'S', "gpg-sign", &sign_commit, N_("key-id"),
	  N_("GPG sign commit"), PARSE_OPT_OPTARG, NULL, (intptr_t) "" },
	OPT_AUTOSTASH(&autostash),
	OPT_BOOL(0, "overwrite-ignore", &overwrite_ignore, N_("update ignored files (default)")),
	OPT_BOOL(0, "signoff", &signoff, N_("add a Signed-off-by trailer")),
	OPT_BOOL(0, "no-verify", &no_verify, N_("bypass pre-merge-commit and commit-msg hooks")),
	OPT_END()
};

static int save_state(struct object_id *stash)
{
	int len;
	struct child_process cp = CHILD_PROCESS_INIT;
	struct strbuf buffer = STRBUF_INIT;
	int rc = -1;

	strvec_pushl(&cp.args, "stash", "create", NULL);
	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)		/* no changes */
		goto out;
	strbuf_setlen(&buffer, buffer.len-1);
	if (get_oid(buffer.buf, stash))
		die(_("not a valid object: %s"), buffer.buf);
	rc = 0;
out:
	strbuf_release(&buffer);
	return rc;
}

static void read_empty(const struct object_id *oid, int verbose)
{
	int i = 0;
	const char *args[7];

	args[i++] = "read-tree";
	if (verbose)
		args[i++] = "-v";
	args[i++] = "-m";
	args[i++] = "-u";
	args[i++] = empty_tree_oid_hex();
	args[i++] = oid_to_hex(oid);
	args[i] = NULL;

	if (run_command_v_opt(args, RUN_GIT_CMD))
		die(_("read-tree failed"));
}

static void reset_hard(const struct object_id *oid, 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++] = oid_to_hex(oid);
	args[i] = NULL;

	if (run_command_v_opt(args, RUN_GIT_CMD))
		die(_("read-tree failed"));
}

static void restore_state(const struct object_id *head,
			  const struct object_id *stash)
{
	struct strbuf sb = STRBUF_INIT;
	const char *args[] = { "stash", "apply", NULL, NULL };

	if (is_null_oid(stash))
		return;

	reset_hard(head, 1);

	args[2] = oid_to_hex(stash);

	/*
	 * It is OK to ignore error here, for example when there was
	 * nothing to restore.
	 */
	run_command_v_opt(args, RUN_GIT_CMD);

	strbuf_release(&sb);
	refresh_cache(REFRESH_QUIET);
}

/* This is called when no merge was necessary. */
static void finish_up_to_date(void)
{
	if (verbosity >= 0) {
		if (squash)
			puts(_("Already up to date. (nothing to squash)"));
		else
			puts(_("Already up to date."));
	}
	remove_merge_branch_state(the_repository);
}

static void squash_message(struct commit *commit, struct commit_list *remoteheads)
{
	struct rev_info rev;
	struct strbuf out = STRBUF_INIT;
	struct commit_list *j;
	struct pretty_print_context ctx = {0};

	printf(_("Squash commit -- not updating HEAD\n"));

	repo_init_revisions(the_repository, &rev, NULL);
	diff_merges_suppress(&rev);
	rev.commit_format = CMIT_FMT_MEDIUM;

	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"));

	ctx.abbrev = rev.abbrev;
	ctx.date_mode = rev.date_mode;
	ctx.fmt = rev.commit_format;

	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",
			oid_to_hex(&commit->object.oid));
		pretty_print_commit(&ctx, commit, &out);
	}
	write_file_buf(git_path_squash_msg(the_repository), out.buf, out.len);
	strbuf_release(&out);
	release_revisions(&rev);
}

static void finish(struct commit *head_commit,
		   struct commit_list *remoteheads,
		   const struct object_id *new_head, const char *msg)
{
	struct strbuf reflog_message = STRBUF_INIT;
	const struct object_id *head = &head_commit->object.oid;

	if (!msg)
		strbuf_addstr(&reflog_message, getenv("GIT_REFLOG_ACTION"));
	else {
		if (verbosity >= 0)
			printf("%s\n", msg);
		strbuf_addf(&reflog_message, "%s: %s",
			getenv("GIT_REFLOG_ACTION"), msg);
	}
	if (squash) {
		squash_message(head_commit, remoteheads);
	} else {
		if (verbosity >= 0 && !merge_msg.len)
			printf(_("No merge message -- not updating HEAD\n"));
		else {
			update_ref(reflog_message.buf, "HEAD", new_head, head,
				   0, UPDATE_REFS_DIE_ON_ERR);
			/*
			 * We ignore errors in 'gc --auto', since the
			 * user should see them.
			 */
			run_auto_maintenance(verbosity < 0);
		}
	}
	if (new_head && show_diffstat) {
		struct diff_options opts;
		repo_diff_setup(the_repository, &opts);
		opts.stat_width = -1; /* use full terminal width */
		opts.stat_graph_width = -1; /* respect statGraphWidth config */
		opts.output_format |=
			DIFF_FORMAT_SUMMARY | DIFF_FORMAT_DIFFSTAT;
		opts.detect_rename = DIFF_DETECT_RENAME;
		diff_setup_done(&opts);
		diff_tree_oid(head, new_head, "", &opts);
		diffcore_std(&opts);
		diff_flush(&opts);
	}

	/* Run a post-merge hook */
	run_hooks_l("post-merge", squash ? "1" : "0", NULL);

	apply_autostash(git_path_merge_autostash(the_repository));
	strbuf_release(&reflog_message);
}

/* Get the name for the merge commit's message. */
static void merge_name(const char *remote, struct strbuf *msg)
{
	struct commit *remote_head;
	struct object_id branch_head;
	struct strbuf buf = STRBUF_INIT;
	struct strbuf bname = STRBUF_INIT;
	struct merge_remote_desc *desc;
	const char *ptr;
	char *found_ref = NULL;
	int len, early;

	strbuf_branchname(&bname, remote, 0);
	remote = bname.buf;

	oidclr(&branch_head);
	remote_head = get_merge_parent(remote);
	if (!remote_head)
		die(_("'%s' does not point to a commit"), remote);

	if (dwim_ref(remote, strlen(remote), &branch_head, &found_ref, 0) > 0) {
		if (starts_with(found_ref, "refs/heads/")) {
			strbuf_addf(msg, "%s\t\tbranch '%s' of .\n",
				    oid_to_hex(&branch_head), remote);
			goto cleanup;
		}
		if (starts_with(found_ref, "refs/tags/")) {
			strbuf_addf(msg, "%s\t\ttag '%s' of .\n",
				    oid_to_hex(&branch_head), remote);
			goto cleanup;
		}
		if (starts_with(found_ref, "refs/remotes/")) {