#include "cache.h"
#include "config.h"
#include "lockfile.h"
#include "dir.h"
#include "object-store.h"
#include "object.h"
#include "commit.h"
#include "sequencer.h"
#include "tag.h"
#include "run-command.h"
#include "exec-cmd.h"
#include "utf8.h"
#include "cache-tree.h"
#include "diff.h"
#include "revision.h"
#include "rerere.h"
#include "merge-recursive.h"
#include "refs.h"
#include "argv-array.h"
#include "quote.h"
#include "trailer.h"
#include "log-tree.h"
#include "wt-status.h"
#include "hashmap.h"
#include "notes-utils.h"
#include "sigchain.h"
#include "unpack-trees.h"
#include "worktree.h"
#include "oidmap.h"
#include "oidset.h"
#include "commit-slab.h"
#include "alias.h"

#define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"

const char sign_off_header[] = "Signed-off-by: ";
static const char cherry_picked_prefix[] = "(cherry picked from commit ";

GIT_PATH_FUNC(git_path_commit_editmsg, "COMMIT_EDITMSG")

GIT_PATH_FUNC(git_path_seq_dir, "sequencer")

static GIT_PATH_FUNC(git_path_todo_file, "sequencer/todo")
static GIT_PATH_FUNC(git_path_opts_file, "sequencer/opts")
static GIT_PATH_FUNC(git_path_head_file, "sequencer/head")
static GIT_PATH_FUNC(git_path_abort_safety_file, "sequencer/abort-safety")

static GIT_PATH_FUNC(rebase_path, "rebase-merge")
/*
 * The file containing rebase commands, comments, and empty lines.
 * This file is created by "git rebase -i" then edited by the user. As
 * the lines are processed, they are removed from the front of this
 * file and written to the tail of 'done'.
 */
static GIT_PATH_FUNC(rebase_path_todo, "rebase-merge/git-rebase-todo")
/*
 * The rebase command lines that have already been processed. A line
 * is moved here when it is first handled, before any associated user
 * actions.
 */
static GIT_PATH_FUNC(rebase_path_done, "rebase-merge/done")
/*
 * The file to keep track of how many commands were already processed (e.g.
 * for the prompt).
 */
static GIT_PATH_FUNC(rebase_path_msgnum, "rebase-merge/msgnum");
/*
 * The file to keep track of how many commands are to be processed in total
 * (e.g. for the prompt).
 */
static GIT_PATH_FUNC(rebase_path_msgtotal, "rebase-merge/end");
/*
 * The commit message that is planned to be used for any changes that
 * need to be committed following a user interaction.
 */
static GIT_PATH_FUNC(rebase_path_message, "rebase-merge/message")
/*
 * The file into which is accumulated the suggested commit message for
 * squash/fixup commands. When the first of a series of squash/fixups
 * is seen, the file is created and the commit message from the
 * previous commit and from the first squash/fixup commit are written
 * to it. The commit message for each subsequent squash/fixup commit
 * is appended to the file as it is processed.
 */
static GIT_PATH_FUNC(rebase_path_squash_msg, "rebase-merge/message-squash")
/*
 * If the current series of squash/fixups has not yet included a squash
 * command, then this file exists and holds the commit message of the
 * original "pick" commit.  (If the series ends without a "squash"
 * command, then this can be used as the commit message of the combined
 * commit without opening the editor.)
 */
static GIT_PATH_FUNC(rebase_path_fixup_msg, "rebase-merge/message-fixup")
/*
 * This file contains the list fixup/squash commands that have been
 * accumulated into message-fixup or message-squash so far.
 */
static GIT_PATH_FUNC(rebase_path_current_fixups, "rebase-merge/current-fixups")
/*
 * A script to set the GIT_AUTHOR_NAME, GIT_AUTHOR_EMAIL, and
 * GIT_AUTHOR_DATE that will be used for the commit that is currently
 * being rebased.
 */
static GIT_PATH_FUNC(rebase_path_author_script, "rebase-merge/author-script")
/*
 * When an "edit" rebase command is being processed, the SHA1 of the
 * commit to be edited is recorded in this file.  When "git rebase
 * --continue" is executed, if there are any staged changes then they
 * will be amended to the HEAD commit, but only provided the HEAD
 * commit is still the commit to be edited.  When any other rebase
 * command is processed, this file is deleted.
 */
static GIT_PATH_FUNC(rebase_path_amend, "rebase-merge/amend")
/*
 * When we stop at a given patch via the "edit" command, this file contains
 * the abbreviated commit name of the corresponding patch.
 */
static GIT_PATH_FUNC(rebase_path_stopped_sha, "rebase-merge/stopped-sha")
/*
 * For the post-rewrite hook, we make a list of rewritten commits and
 * their new sha1s.  The rewritten-pending list keeps the sha1s of
 * commits that have been processed, but not committed yet,
 * e.g. because they are waiting for a 'squash' command.
 */
static GIT_PATH_FUNC(rebase_path_rewritten_list, "rebase-merge/rewritten-list")
static GIT_PATH_FUNC(rebase_path_rewritten_pending,
	"rebase-merge/rewritten-pending")

/*
 * The path of the file containig the OID of the "squash onto" commit, i.e.
 * the dummy commit used for `reset [new root]`.
 */
static GIT_PATH_FUNC(rebase_path_squash_onto, "rebase-merge/squash-onto")

/*
 * The path of the file listing refs that need to be deleted after the rebase
 * finishes. This is used by the `label` command to record the need for cleanup.
 */
static GIT_PATH_FUNC(rebase_path_refs_to_delete, "rebase-merge/refs-to-delete")

/*
 * The following files are written by git-rebase just after parsing the
 * command-line (and are only consumed, not modified, by the sequencer).
 */
static GIT_PATH_FUNC(rebase_path_gpg_sign_opt, "rebase-merge/gpg_sign_opt")
static GIT_PATH_FUNC(rebase_path_orig_head, "rebase-merge/orig-head")
static GIT_PATH_FUNC(rebase_path_verbose, "rebase-merge/verbose")
static GIT_PATH_FUNC(rebase_path_signoff, "rebase-merge/signoff")
static GIT_PATH_FUNC(rebase_path_head_name, "rebase-merge/head-name")
static GIT_PATH_FUNC(rebase_path_onto, "rebase-merge/onto")
static GIT_PATH_FUNC(rebase_path_autostash, "rebase-merge/autostash")
static GIT_PATH_FUNC(rebase_path_strategy, "rebase-merge/strategy")
static GIT_PATH_FUNC(rebase_path_strategy_opts, "rebase-merge/strategy_opts")
static GIT_PATH_FUNC(rebase_path_allow_rerere_autoupdate, "rebase-merge/allow_rerere_autoupdate")

static int git_sequencer_config(const char *k, const char *v, void *cb)
{
	struct replay_opts *opts = cb;
	int status;

	if (!strcmp(k, "commit.cleanup")) {
		const char *s;

		status = git_config_string(&s, k, v);
		if (status)
			return status;

		if (!strcmp(s, "verbatim"))
			opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_NONE;
		else if (!strcmp(s, "whitespace"))
			opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_SPACE;
		else if (!strcmp(s, "strip"))
			opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_ALL;
		else if (!strcmp(s, "scissors"))
			opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_SPACE;
		else
			warning(_("invalid commit message cleanup mode '%s'"),
				  s);

		free((char *)s);
		return status;
	}

	if (!strcmp(k, "commit.gpgsign")) {
		opts->gpg_sign = git_config_bool(k, v) ? xstrdup("") : NULL;
		return 0;
	}

	status = git_gpg_config(k, v, NULL);
	if (status)
		return status;

	return git_diff_basic_config(k, v, NULL);
}

void sequencer_init_config(struct replay_opts *opts)
{
	opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_NONE;
	git_config(git_sequencer_config, opts);
}

static inline int is_rebase_i(const struct replay_opts *opts)
{
	return opts->action == REPLAY_INTERACTIVE_REBASE;
}

static const char *get_dir(const struct replay_opts *opts)
{
	if (is_rebase_i(opts))
		return rebase_path();
	return git_path_seq_dir();
}

static const char *get_todo_path(const struct replay_opts *opts)
{
	if (is_rebase_i(opts))
		return rebase_path_todo();
	return git_path_todo_file();
}

/*
 * Returns 0 for non-conforming footer
 * Returns 1 for conforming footer
 * Returns 2 when sob exists within conforming footer
 * Returns 3 when sob exists within conforming footer as last entry
 */
static int has_conforming_footer(struct strbuf *sb, struct strbuf *sob,
	int ignore_footer)
{
	struct trailer_info info;
	int i;
	int found_sob = 0, found_sob_last = 0;

	trailer_info_get(&info, sb->buf);

	if (info.trailer_start == info.trailer_end)
		return 0;

	for (i = 0; i < info.trailer_nr; i++)
		if (sob && !strncmp(info.trailers[i], sob->buf, sob->len)) {
			found_sob = 1;
			if (i == info.trailer_nr - 1)
				found_sob_last = 1;
		}

	trailer_info_release(&info);

	if (found_sob_last)
		return 3;
	if (found_sob)
		return 2;
	return 1;
}

static const char *gpg_sign_opt_quoted(struct replay_opts *opts)
{
	static struct strbuf buf = STRBUF_INIT;

	strbuf_reset(&buf);
	if (opts->gpg_sign)
		sq_quotef(&buf, "-S%s", opts->gpg_sign);
	return buf.buf;
}

int sequencer_remove_state(struct replay_opts *opts)
{
	struct strbuf buf = STRBUF_INIT;
	int i;

	if (is_rebase_i(opts) &&
	    strbuf_read_file(&buf, rebase_path_refs_to_delete(), 0) > 0) {
		char *p = buf.buf;
		while (*p) {
			char *eol = strchr(p, '\n');
			if (eol)
				*eol = '\0';
			if (delete_ref("(rebase -i) cleanup", p, NULL, 0) < 0)
				warning(_("could not delete '%s'"), p);
			if (!eol)
				break;
			p = eol + 1;
		}
	}

	free(opts->gpg_sign);
	free(opts->strategy);
	for (i = 0; i < opts->xopts_nr; i++)
		free(opts->xopts[i]);
	free(opts->xopts);
	strbuf_release(&opts->current_fixups);

	strbuf_reset(&buf);
	strbuf_addstr(&buf, get_dir(opts));
	remove_dir_recursively(&buf, 0);
	strbuf_release(&buf);

	return 0;
}

static const char *action_name(const struct replay_opts *opts)
{
	switch (opts->action) {
	case REPLAY_REVERT:
		return N_("revert");
	case REPLAY_PICK:
		return N_("cherry-pick");
	case REPLAY_INTERACTIVE_REBASE:
		return N_("rebase -i");
	}
	die(_("Unknown action: %d"), opts->action);
}

struct commit_message {
	char *parent_label;
	char *label;
	char *subject;
	const char *message;
};

static const char *short_commit_name(struct commit *commit)
{
	return find_unique_abbrev(&commit->object.oid, DEFAULT_ABBREV);
}

static int get_message(struct commit *commit, struct commit_message *out)
{
	const char *abbrev, *subject;
	int subject_len;

	out->message = logmsg_reencode(commit, NULL, get_commit_output_encoding());
	abbrev = short_commit_name(commit);

	subject_len = find_commit_subject(out->message, &subject);

	out->subject = xmemdupz(subject, subject_len);
	out->label = xstrfmt("%s... %s", abbrev, out->subject);
	out->parent_label = xstrfmt("parent of %s", out->label);

	return 0;
}

static void free_message(struct commit *commit, struct commit_message *msg)
{
	free(msg->parent_label);
	free(msg->label);
	free(msg->subject);
	unuse_commit_buffer(commit, msg->message);
}

static void print_advice(int show_hint, struct replay_opts *opts)
{
	char *msg = getenv("GIT_CHERRY_PICK_HELP");

	if (msg) {
		fprintf(stderr, "%s\n", msg);
		/*
		 * A conflict has occurred but the porcelain
		 * (typically rebase --interactive) wants to take care
		 * of the commit itself so remove CHERRY_PICK_HEAD
		 */
		unlink(git_path_cherry_pick_head(the_repository));
		return;
	}

	if (show_hint) {
		if (opts->no_commit)
			advise(_("after resolving the conflicts, mark the corrected paths\n"
				 "with 'git add <paths>' or 'git rm <paths>'"));
		else
			advise(_("after resolving the conflicts, mark the corrected paths\n"
				 "with 'git add <paths>' or 'git rm <paths>'\n"
				 "and commit the result with 'git commit'"));
	}
}

static int write_message(const void *buf, size_t len, const char *filename,
			 int append_eol)
{
	struct lock_file msg_file = LOCK_INIT;

	int msg_fd = hold_lock_file_for_update(&msg_file, filename, 0);
	if (msg_fd < 0)
		return error_errno(_("could not lock '%s'"), filename);
	if (write_in_full(msg_fd, buf, len) < 0) {
		error_errno(_("could not write to '%s'"), filename);
		rollback_lock_file(&msg_file);
		return -1;
	}
	if (append_eol && write(msg_fd, "\n", 1) < 0) {
		error_errno(_("could not write eol to '%s'"), filename);
		rollback_lock_file(&msg_file);
		return -1;
	}
	if (commit_lock_file(&msg_file) < 0)
		return error(_("failed to finalize '%s'"), filename);

	return 0;
}

/*
 * Reads a file that was presumably written by a shell script, i.e. with an
 * end-of-line marker that needs to be stripped.
 *
 * Note that only the last end-of-line marker is stripped, consistent with the
 * behavior of "$(cat path)" in a shell script.
 *
 * Returns 1 if the file was read, 0 if it could not be read or does not exist.
 */
static int read_oneliner(struct strbuf *buf,
	const char *path, int skip_if_empty)
{
	int orig_len = buf->len;

	if (!file_exists(path))
		return 0;

	if (strbuf_read_file(buf, path, 0) < 0) {
		warning_errno(_("could not read '%s'"), path);
		return 0;
	}

	if (buf->len > orig_len && buf->buf[buf->len - 1] == '\n') {
		if (--buf->len > orig_len && buf->buf[buf->len - 1] == '\r')
			--buf->len;
		buf->buf[buf->len] = '\0';
	}

	if (skip_if_empty && buf->len == orig_len)
		return 0;

	return 1;
}

static struct tree *empty_tree(void)
{
	return lookup_tree(the_repository, the_repository->hash_algo->empty_tree);
}

static int error_dirty_index(struct replay_opts *opts)
{
	if (read_cache_unmerged())
		return error_resolve_conflict(_(action_name(opts)));

	error(_("your local changes would be overwritten by %s."),
		_(action_name(opts)));

	if (advice_commit_before_merge)
		advise(_("commit your changes or stash them to proceed."));
	return -1;
}

static void update_abort_safety_file(void)
{
	struct object_id head;

	/* Do nothing on a single-pick */
	if (!file_exists(git_path_seq_dir()))
		return;

	if (!get_oid("HEAD", &head))
		write_file(git_path_abort_safety_file(), "%s", oid_to_hex(&head));
	else
		write_file(git_path_abort_safety_file(), "%s", "");
}

static int fast_forward_to(const struct object_id *to, const struct object_id *from,
			int unborn, struct replay_opts *opts)
{
	struct ref_transaction *transaction;
	struct strbuf sb = STRBUF_INIT;
	struct strbuf err = STRBUF_INIT;

	read_cache();
	if (checkout_fast_forward(from, to, 1))
		return -1; /* the callee should have complained already */

	strbuf_addf(&sb, _("%s: fast-forward"), _(action_name(opts)));

	transaction = ref_transaction_begin(&err);
	if (!transaction ||
	    ref_transaction_update(transaction, "HEAD",
				   to, unborn && !is_rebase_i(opts) ?
				   &null_oid : from,
				   0, sb.buf, &err) ||
	    ref_transaction_commit(transaction, &err)) {
		ref_transaction_free(transaction);
		error("%s", err.buf);
		strbuf_release(&sb);
		strbuf_release(&err);
		return -1;
	}

	strbuf_release(&sb);
	strbuf_release(&err);
	ref_transaction_free(transaction);
	update_abort_safety_file();
	return 0;
}

void append_conflicts_hint(struct strbuf *msgbuf)
{
	int i;

	strbuf_addch(msgbuf, '\n');
	strbuf_commented_addf(msgbuf, "Conflicts:\n");
	for (i = 0; i < active_nr;) {
		const struct cache_entry *ce = active_cache[i++];
		if (ce_stage(ce)) {
			strbuf_commented_addf(msgbuf, "\t%s\n", ce->name);
			while (i < active_nr && !strcmp(ce->name,
							active_cache[i]->name))
				i++;
		}
	}
}

static int do_recursive_merge(struct commit *base, struct commit *next,
			      const char *base_label, const char *next_label,
			      struct object_id *head, struct strbuf *msgbuf,
			      struct replay_opts *opts)
{
	struct merge_options o;
	struct tree *result, *next_tree, *base_tree, *head_tree;
	int clean;
	char **xopt;
	struct lock_file index_lock = LOCK_INIT;

	if (hold_locked_index(&index_lock, LOCK_REPORT_ON_ERROR) < 0)
		return -1;

	read_cache();

	init_merge_options(&o);
	o.ancestor = base ? base_label : "(empty tree)";
	o.branch1 = "HEAD";
	o.branch2 = next ? next_label : "(empty tree)";
	if (is_rebase_i(opts))
		o.buffer_output = 2;
	o.show_rename_progress = 1;

	head_tree = parse_tree_indirect(head);
	next_tree = next ? get_commit_tree(next) : empty_tree();
	base_tree = base ? get_commit_tree(base) : empty_tree();

	for (xopt = opts->xopts; xopt != opts->xopts + opts->xopts_nr; xopt++)
		parse_merge_opt(&o, *xopt);

	clean = merge_trees(&o,
			    head_tree,
			    next_tree, base_tree, &result);
	if (is_rebase_i(opts) && clean <= 0)
		fputs(o.obuf.buf, stdout);
	strbuf_release(&o.obuf);
	diff_warn_rename_limit("merge.renamelimit", o.needed_rename_limit, 0);
	if (clean < 0) {
		rollback_lock_file(&index_lock);
		return clean;
	}

	if (write_locked_index(&the_index, &index_lock,
			       COMMIT_LOCK | SKIP_IF_UNCHANGED))
		/*
		 * TRANSLATORS: %s will be "revert", "cherry-pick" or
		 * "rebase -i".
		 */
		return error(_("%s: Unable to write new index file"),
			_(action_name(opts)));

	if (!clean)
		append_conflicts_hint(msgbuf);

	return !clean;
}

static struct object_id *get_cache_tree_oid(void)
{
	if (!active_cache_tree)
		active_cache_tree = cache_tree();

	if (!cache_tree_fully_valid(active_cache_tree))
		if (cache_tree_update(&the_index, 0)) {
			error(_("unable to update cache tree"));
			return NULL;
		}

	return &active_cache_tree->oid;
}

static int is_index_unchanged(void)
{
	struct object_id head_oid, *cache_tree_oid;
	struct commit *head_commit;

	if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, &head_oid, NULL))
		return error(_("could not resolve HEAD commit"));

	head_commit = lookup_commit(&head_oid);

	/*
	 * If head_commit is NULL, check_commit, called from
	 * lookup_commit, would have indicated that head_commit is not
	 * a commit object already.  parse_commit() will return failure
	 * without further complaints in such a case.  Otherwise, if
	 * the commit is invalid, parse_commit() will complain.  So
	 * there is nothing for us to say here.  Just return failure.
	 */
	if (parse_commit(head_commit))
		return -1;

	if (!(cache_tree_oid = get_cache_tree_oid()))
		return -1;

	return !oidcmp(cache_tree_oid, get_commit_tree_oid(head_commit));
}

static int write_author_script(const char *message)
{
	struct strbuf buf = STRBUF_INIT;
	const char *eol;
	int res;

	for (;;)
		if (!*message || starts_with(message, "\n")) {
missing_author:
			/* Missing 'author' line? */
			unlink(rebase_path_author_script());
			return 0;
		} else if (skip_prefix(message, "author ", &message))
			break;
		else if ((eol = strchr(message, '\n')))
			message = eol + 1;
		else
			goto missing_author;

	strbuf_addstr(&buf, "GIT_AUTHOR_NAME='");
	while (*message && *message != '\n' && *message != '\r')
		if (skip_prefix(message, " <", &message))
			break;
		else if (*message != '\'')
			strbuf_addch(&buf, *(message++));
		else
			strbuf_addf(&buf, "'\\\\%c'", *(message++));
	strbuf_addstr(&buf, "'\nGIT_AUTHOR_EMAIL='");
	while (*message && *message != '\n' && *message != '\r')
		if (skip_prefix(message, "> ", &message))
			break;
		else if (*message != '\'')
			strbuf_addch(&buf, *(message++));
		else
			strbuf_addf(&buf, "'\\\\%c'", *(message++));
	strbuf_addstr(&buf, "'\nGIT_AUTHOR_DATE='@");
	while (*message && *message != '\n' && *message != '\r')
		if (*message != '\'')
			strbuf_addch(&buf, *(message++));
		else
			strbuf_addf(&buf, "'\\\\%c'", *(message++));
	res = write_message(buf.buf, buf.len, rebase_path_author_script(), 1);
	strbuf_release(&buf);
	return res;
}

/*
 * Read a list of environment variable assignments (such as the author-script
 * file) into an environment block. Returns -1 on error, 0 otherwise.
 */
static int read_env_script(struct argv_array *env)
{
	struct strbuf script = STRBUF_INIT;
	int i, count = 0;
	char *p, *p2;

	if (strbuf_read_file(&script, rebase_path_author_script(), 256) <= 0)
		return -1;

	for (p = script.buf; *p; p++)
		if (skip_prefix(p, "'\\\\''", (const char **)&p2))
			strbuf_splice(&script, p - script.buf, p2 - p, "'", 1);
		else if (*p == '\'')
			strbuf_splice(&script, p-- - script.buf, 1, "", 0);
		else if (*p == '\n') {
			*p = '\0';
			count++;
		}

	for (i = 0, p = script.buf; i < count; i++) {
		argv_array_push(env, p);
		p += strlen(p) + 1;
	}

	return 0;
}

static char *get_author(const char *message)
{
	size_t len;
	const char *a;

	a = find_commit_header(message, "author", &len);
	if (a)
		return xmemdupz(a, len);

	return NULL;
}

/* Read author-script and return an ident line (author <email> timestamp) */
static const char *read_author_ident(struct strbuf *buf)
{
	const char *keys[] = {
		"GIT_AUTHOR_NAME=", "GIT_AUTHOR_EMAIL=", "GIT_AUTHOR_DATE="
	};
	char *in, *out, *eol;
	int i = 0, len;

	if (strbuf_read_file(buf, rebase_path_author_script(), 256) <= 0)
		return NULL;

	/* dequote values and construct ident line in-place */
	for (in = out = buf->buf; i < 3 && in - buf->buf < buf->len; i++) {
		if (!skip_prefix(in, keys[i], (const char **)&in)) {
			warning("could not parse '%s' (looking for '%s'",
				rebase_path_author_script(), keys[i]);
			return NULL;
		}

		eol = strchrnul(in, '\n');
		*eol = '\0';
		sq_dequote(in);
		len = strlen(in);

		if (i > 0) /* separate values by spaces */
			*(out++) = ' ';
		if (i == 1) /* email needs to be surrounded by <...> */
			*(out++) = '<';
		memmove(out, in, len);
		out += len;
		if (i == 1) /* email needs to be surrounded by <...> */
			*(out++) = '>';
		in = eol + 1;
	}

	if (i < 3) {
		warning("could not parse '%s' (looking for '%s')",
			rebase_path_author_script(), keys[i]);
		return NULL;
	}

	buf->len = out - buf->buf;
	return buf->buf;
}

static const char staged_changes_advice[] =
N_("you have staged changes in your working tree\n"
"If these changes are meant to be squashed into the previous commit, run:\n"
"\n"
"  git commit --amend %s\n"
"\n"
"If they are meant to go into a new commit, run:\n"
"\n"
"  git commit %s\n"
"\n"
"In both cases, once you're done, continue with:\n"
"\n"
"  git rebase --continue\n");

#define ALLOW_EMPTY (1<<0)
#define EDIT_MSG    (1<<1)
#define AMEND_MSG   (1<<2)
#define CLEANUP_MSG (1<<3)
#define VERIFY_MSG  (1<<4)
#define CREATE_ROOT_COMMIT (1<<5)

/*
 * If we are cherry-pick, and if the merge did not result in
 * hand-editing, we will hit this commit and inherit the original
 * author date and name.
 *
 * If we are revert, or if our cherry-pick results in a hand merge,
 * we had better say that the current user is responsible for that.
 *
 * An exception is when run_git_commit() is called during an
 * interactive rebase: in that case, we will want to retain the
 * author metadata.
 */
static int run_git_commit(const char *defmsg, struct replay_opts *opts,
			  unsigned int flags)
{
	struct child_process cmd = CHILD_PROCESS_INIT;
	const char *value;

	if ((flags & CREATE_ROOT_COMMIT) && !(flags & AMEND_MSG)) {
		struct strbuf msg = STRBUF_INIT, script = STRBUF_INIT;
		const char *author = is_rebase_i(opts) ?
			read_author_ident(&script) : NULL;
		struct object_id root_commit, *cache_tree_oid;
		int res = 0;

		if (!defmsg)
			BUG("root commit without message");

		if (!(cache_tree_oid = get_cache_tree_oid()))
			res = -1;

		if (!res)
			res = strbuf_read_file(&msg, defmsg, 0);

		if (res <= 0)
			res = error_errno(_("could not read '%s'"), defmsg);
		else
			res = commit_tree(msg.buf, msg.len, cache_tree_oid,
					  NULL, &root_commit, author,
					  opts->gpg_sign);

		strbuf_release(&msg);
		strbuf_release(&script);
		if (!res) {
			update_ref(NULL, "CHERRY_PICK_HEAD", &root_commit, NULL,
				   REF_NO_DEREF, UPDATE_REFS_MSG_ON_ERR);
			res = update_ref(NULL, "HEAD", &root_commit, NULL, 0,
					 UPDATE_REFS_MSG_ON_ERR);
		}
		return res < 0 ? error(_("writing root commit")) : 0;
	}

	cmd.git_cmd = 1;

	if (is_rebase_i(opts)) {
		if (!(flags & EDIT_MSG)) {
			cmd.stdout_to_stderr = 1;
			cmd.err = -1;
		}

		if (read_env_script(&cmd.env_array)) {
			const char *gpg_opt = gpg_sign_opt_quoted(opts);

			return error(_(staged_changes_advice),
				     gpg_opt, gpg_opt);
		}
	}

	argv_array_push(&cmd.args, "commit");

	if (!(flags & VERIFY_MSG))
		argv_array_push(&cmd.args, "-n");
	if ((flags & AMEND_MSG))
		argv_array_push(&cmd.args, "--amend");
	if (opts->gpg_sign)
		argv_array_pushf(&cmd.args, "-S%s", opts->gpg_sign);
	if (defmsg)
		argv_array_pushl(&cmd.args, "-F", defmsg, NULL);
	else if (!(flags & EDIT_MSG))
		argv_array_pushl(&cmd.args, "-C", "HEAD", NULL);
	if ((flags & CLEANUP_MSG))
		argv_array_push(&cmd.args, "--cleanup=strip");
	if ((flags & EDIT_MSG))
		argv_array_push(&cmd.args, "-e");
	else if (!(flags & CLEANUP_MSG) &&
		 !opts->signoff && !opts->record_origin &&
		 git_config_get_value("commit.cleanup", &value))
		argv_array_push(&cmd.args, "--cleanup=verbatim");

	if ((flags & ALLOW_EMPTY))
		argv_array_push(&cmd.args, "--allow-empty");

	if (opts->allow_empty_message)
		argv_array_push(&cmd.args, "--allow-empty-message");

	if (cmd.err == -1) {
		/* hide stderr on success */
		struct strbuf buf = STRBUF_INIT;
		int rc = pipe_command(&cmd,
				      NULL, 0,
				      /* stdout is already redirected */
				      NULL, 0,
				      &buf, 0);
		if (rc)
			fputs(buf.buf, stderr);
		strbuf_release(&buf);
		return rc;
	}

	return run_command(&cmd);
}

static int rest_is_empty(const struct strbuf *sb, int start)
{
	int i, eol;
	const char *nl;

	/* Check if the rest is just whitespace and Signed-off-by's. */
	for (i = start; i < sb->len; i++) {
		nl = memchr(sb->buf + i, '\n', sb->len - i);
		if (nl)
			eol = nl - sb->buf;
		else
			eol = sb->len;

		if (strlen(sign_off_header) <= eol - i &&
		    starts_with(sb->buf + i, sign_off_header)) {
			i = eol;
			continue;
		}
		while (i < eol)
			if (!isspace(sb->buf[i++]))
				return 0;
	}

	return 1;
}

/*
 * Find out if the message in the strbuf contains only whitespace and
 * Signed-off-by lines.
 */
int message_is_empty(const struct strbuf *sb,
		     enum commit_msg_cleanup_mode cleanup_mode)
{
	if (cleanup_mode == COMMIT_MSG_CLEANUP_NONE && sb->len)
		return 0;
	return rest_is_empty(sb, 0);
}

/*
 * See if the user edited the message in the editor or left what
 * was in the template intact
 */
int template_untouched(const struct strbuf *sb, const char *template_file,
		       enum commit_msg_cleanup_mode cleanup_mode)
{
	struct strbuf tmpl = STRBUF_INIT;
	const char *start;

	if (cleanup_mode == COMMIT_MSG_CLEANUP_NONE && sb->len)
		return 0;

	if (!template_file || strbuf_read_file(&tmpl, template_file, 0) <= 0)
		return 0;

	strbuf_stripspace(&tmpl, cleanup_mode == COMMIT_MSG_CLEANUP_ALL);
	if (!skip_prefix(sb->buf, tmpl.buf, &start))
		start = sb->buf;
	strbuf_release(&tmpl);
	return rest_is_empty(sb, start - sb->buf);
}

int update_head_with_reflog(const struct commit *old_head,
			    const struct object_id *new_head,
			    const char *action, const struct strbuf *msg,
			    struct strbuf *err)
{
	struct ref_transaction *transaction;
	struct strbuf sb = STRBUF_INIT;
	const char *nl;
	int ret = 0;

	if (action) {
		strbuf_addstr(&sb, action);
		strbuf_addstr(&sb, ": ");
	}

	nl = strchr(msg->buf, '\n');
	if (nl) {
		strbuf_add(&sb, msg->buf, nl + 1 - msg->buf);
	} else {
		strbuf_addbuf(&sb, msg);
		strbuf_addch(&sb, '\n');
	}

	transaction = ref_transaction_begin(err);
	if (!transaction ||
	    ref_transaction_update(transaction, "HEAD", new_head,
				   old_head ? &old_head->object.oid : &null_oid,
				   0, sb.buf, err) ||
	    ref_transaction_commit(transaction, err)) {
		ret = -1;
	}
	ref_transaction_free(transaction);
	strbuf_release(&sb);

	return ret;
}

static int run_rewrite_hook(const struct object_id *oldoid,
			    const struct object_id *newoid)
{
	struct child_process proc = CHILD_PROCESS_INIT;
	const char *argv[3];
	int code;
	struct strbuf sb = STRBUF_INIT;

	argv[0] = find_hook("post-rewrite");
	if (!argv[0])
		return 0;

	argv[1] = "amend";
	argv[2] = NULL;

	proc.argv = argv;
	proc.in = -1;
	proc.stdout_to_stderr = 1;

	code = start_command(&proc);
	if (code)
		return code;
	strbuf_addf(&sb, "%s %s\n", oid_to_hex(oldoid), oid_to_hex(newoid));
	sigchain_push(SIGPIPE, SIG_IGN);
	write_in_full(proc.in, sb.buf, sb.len);
	close(proc.in);
	strbuf_release(&sb);
	sigchain_pop(SIGPIPE);
	return finish_command(&proc);
}

void commit_post_rewrite(const struct commit *old_head,
			 const struct object_id *new_head)
{
	struct notes_rewrite_cfg *cfg;

	cfg = init_copy_notes_for_rewrite("amend");
	if (cfg) {
		/* we are amending, so old_head is not NULL */
		copy_note_for_rewrite(cfg, &old_head->object.oid, new_head);
		finish_copy_notes_for_rewrite(cfg, "Notes added by 'git commit --amend'");
	}
	run_rewrite_hook(&old_head->object.oid, new_head);
}

static int run_prepare_commit_msg_hook(struct strbuf *msg, const char *commit)
{
	struct argv_array hook_env = ARGV_ARRAY_INIT;
	int ret;
	const char *name;

	name = git_path_commit_editmsg();
	if (write_message(msg->buf, msg->len, name, 0))
		return -1;

	argv_array_pushf(&hook_env, "GIT_INDEX_FILE=%s", get_index_file());
	argv_array_push(&hook_env, "GIT_EDITOR=:");
	if (commit)
		ret = run_hook_le(hook_env.argv, "prepare-commit-msg", name,
				  "commit", commit, NULL);
	else
		ret = run_hook_le(hook_env.argv, "prepare-commit-msg", name,
				  "message", NULL);
	if (ret)
		ret = error(_("'prepare-commit-msg' hook failed"));
	argv_array_clear(&hook_env);

	return ret;
}

static const char implicit_ident_advice_noconfig[] =
N_("Your name and email address were configured automatically based\n"
"on your username and hostname. Please check that they are accurate.\n"
"You can suppress this message by setting them explicitly. Run the\n"
"following command and follow the instructions in your editor to edit\n"
"your configuration file:\n"
"\n"
"    git config --global --edit\n"
"\n"
"After doing this, you may fix the identity used for this commit with:\n"
"\n"
"    git commit --amend --reset-author\n");

static const char implicit_ident_advice_config[] =
N_("Your name and email address were configured automatically based\n"
"on your username and hostname. Please check that they are accurate.\n"
"You can suppress this message by setting them explicitly:\n"
"\n"
"    git config --global user.name \"Your Name\"\n"
"    git config --global user.email you@example.com\n"
"\n"
"After doing this, you may fix the identity used for this commit with:\n"
"\n"
"    git commit --amend --reset-author\n");

static const char *implicit_ident_advice(void)
{
	char *user_config = expand_user_path("~/.gitconfig", 0);
	char *xdg_config = xdg_config_home("config");
	int config_exists = file_exists(user_config) || file_exists(xdg_config);

	free(user_config);
	free(xdg_config);

	if (config_exists)
		return _(implicit_ident_advice_config);
	else
		return _(implicit_ident_advice_noconfig);

}

void print_commit_summary(const char *prefix, const struct object_id *oid,
			  unsigned int flags)
{
	struct rev_info rev;
	struct commit *commit;
	struct strbuf format = STRBUF_INIT;
	const char *head;
	struct pretty_print_context pctx = {0};
	struct strbuf author_ident = STRBUF_INIT;
	struct strbuf committer_ident = STRBUF_INIT;

	commit = lookup_commit(oid);
	if (!commit)
		die(_("couldn't look up newly created commit"));
	if (parse_commit(commit))
		die(_("could not parse newly created commit"));

	strbuf_addstr(&format, "format:%h] %s");

	format_commit_message(commit, "%an <%ae>", &author_ident, &pctx);
	format_commit_message(commit, "%cn <%ce>", &committer_ident, &pctx);
	if (strbuf_cmp(&author_ident, &committer_ident)) {
		strbuf_addstr(&format, "\n Author: ");
		strbuf_addbuf_percentquote(&format, &author_ident);
	}
	if (flags & SUMMARY_SHOW_AUTHOR_DATE) {
		struct strbuf date = STRBUF_INIT;

		format_commit_message(commit, "%ad", &date, &pctx);
		strbuf_addstr(&format, "\n Date: ");
		strbuf_addbuf_percentquote(&format, &date);
		strbuf_release(&date);
	}
	if (!committer_ident_sufficiently_given()) {
		strbuf_addstr(&format, "\n Committer: ");
		strbuf_addbuf_percentquote(&format, &committer_ident);
		if (advice_implicit_identity) {
			strbuf_addch(&format, '\n');
			strbuf_addstr(&format, implicit_ident_advice());
		}
	}
	strbuf_release(&author_ident);
	strbuf_release(&committer_ident);

	init_revisions(&rev, prefix);
	setup_revisions(0, NULL, &rev, NULL);

	rev.diff = 1;
	rev.diffopt.output_format =
		DIFF_FORMAT_SHORTSTAT | DIFF_FORMAT_SUMMARY;

	rev.verbose_header = 1;
	rev.show_root_diff = 1;
	get_commit_format(format.buf, &rev);
	rev.always_show_header = 0;
	rev.diffopt.detect_rename = DIFF_DETECT_RENAME;
	rev.diffopt.break_opt = 0;
	diff_setup_done(&rev.diffopt);

	head = resolve_ref_unsafe("HEAD", 0, NULL, NULL);
	if (!head)
		die_errno(_("unable to resolve HEAD after creating commit"));
	if (!strcmp(head, "HEAD"))
		head = _("detached HEAD");
	else
		skip_prefix(head, "refs/heads/", &head);
	printf("[%s%s ", head, (flags & SUMMARY_INITIAL_COMMIT) ?
						_(" (root-commit)") : "");

	if (!log_tree_commit(&rev, commit)) {
		rev.always_show_header = 1;
		rev.use_terminator = 1;
		log_tree_commit(&rev, commit);
	}

	strbuf_release(&format);
}

static int parse_head(struct commit **head)
{
	struct commit *current_head;
	struct object_id oid;

	if (get_oid("HEAD", &oid)) {
		current_head = NULL;
	} else {
		current_head = lookup_commit_reference(&oid);
		if (!current_head)
			return error(_("could not parse HEAD"));
		if (oidcmp(&oid, &current_head->object.oid)) {
			warning(_("HEAD %s is not a commit!"),
				oid_to_hex(&oid));
		}
		if (parse_commit(current_head))
			return error(_("could not parse HEAD commit"));
	}
	*head = current_head;

	return 0;
}

/*
 * Try to commit without forking 'git commit'. In some cases we need
 * to run 'git commit' to display an error message
 *
 * Returns:
 *  -1 - error unable to commit
 *   0 - success
 *   1 - run 'git commit'
 */
static int try_to_commit(struct strbuf *msg, const char *author,
			 struct replay_opts *opts, unsigned int flags,
			 struct object_id *oid)
{
	struct object_id tree;
	struct commit *current_head;
	struct commit_list *parents = NULL;
	struct commit_extra_header *extra = NULL;
	struct strbuf err = STRBUF_INIT;
	struct strbuf commit_msg = STRBUF_INIT;
	char *amend_author = NULL;
	const char *hook_commit = NULL;
	enum commit_msg_cleanup_mode cleanup;
	int res = 0;

	if (parse_head(&current_head))
		return -1;

	if (flags & AMEND_MSG) {
		const char *exclude_gpgsig[] = { "gpgsig", NULL };
		const char *out_enc = get_commit_output_encoding();
		const char *message = logmsg_reencode(current_head, NULL,
						      out_enc);

		if (!msg) {
			const char *orig_message = NULL;

			find_commit_subject(message, &orig_message);
			msg = &commit_msg;
			strbuf_addstr(msg, orig_message);
			hook_commit = "HEAD";
		}
		author = amend_author = get_author(message);
		unuse_commit_buffer(current_head, message);
		if (!author) {
			res = error(_("unable to parse commit author"));
			goto out;
		}
		parents = copy_commit_list(current_head->parents);
		extra = read_commit_extra_headers(current_head, exclude_gpgsig);
	} else if (current_head) {
		commit_list_insert(current_head, &parents);
	}

	if (write_cache_as_tree(&tree, 0, NULL)) {
		res = error(_("git write-tree failed to write a tree"));
		goto out;
	}

	if (!(flags & ALLOW_EMPTY) && !oidcmp(current_head ?
					      get_commit_tree_oid(current_head) :
					      the_hash_algo->empty_tree, &tree)) {
		res = 1; /* run 'git commit' to display error message */
		goto out;
	}

	if (find_hook("prepare-commit-msg")) {
		res = run_prepare_commit_msg_hook(msg, hook_commit);
		if (res)
			goto out;
		if (strbuf_read_file(&commit_msg, git_path_commit_editmsg(),
				     2048) < 0) {
			res = error_errno(_("unable to read commit message "
					      "from '%s'"),
					    git_path_commit_editmsg());
			goto out;
		}
		msg = &commit_msg;
	}

	cleanup = (flags & CLEANUP_MSG) ? COMMIT_MSG_CLEANUP_ALL :
					  opts->default_msg_cleanup;

	if (cleanup != COMMIT_MSG_CLEANUP_NONE)
		strbuf_stripspace(msg, cleanup == COMMIT_MSG_CLEANUP_ALL);
	if (!opts->allow_empty_message && message_is_empty(msg, cleanup)) {
		res = 1; /* run 'git commit' to display error message */
		goto out;
	}

	reset_ident_date();

	if (commit_tree_extended(msg->buf, msg->len, &tree, parents,
				 oid, author, opts->gpg_sign, extra)) {
		res = error(_("failed to write commit object"));
		goto out;
	}

	if (update_head_with_reflog(current_head, oid,
				    getenv("GIT_REFLOG_ACTION"), msg, &err)) {
		res = error("%s", err.buf);
		goto out;
	}

	if (flags & AMEND_MSG)
		commit_post_rewrite(current_head, oid);

out:
	free_commit_extra_headers(extra);
	strbuf_release(&err);
	strbuf_release(&commit_msg);
	free(amend_author);

	return res;
}

static int do_commit(const char *msg_file, const char *author,
		     struct replay_opts *opts, unsigned int flags)
{
	int res = 1;

	if (!(flags & EDIT_MSG) && !(flags & VERIFY_MSG) &&
	    !(flags & CREATE_ROOT_COMMIT)) {
		struct object_id oid;
		struct strbuf sb = STRBUF_INIT;

		if (msg_file && strbuf_read_file(&sb, msg_file, 2048) < 0)
			return error_errno(_("unable to read commit message "
					     "from '%s'"),
					   msg_file);

		res = try_to_commit(msg_file ? &sb : NULL, author, opts, flags,
				    &oid);
		strbuf_release(&sb);
		if (!res) {
			unlink(git_path_cherry_pick_head(the_repository));
			unlink(git_path_merge_msg(the_repository));
			if (!is_rebase_i(opts))
				print_commit_summary(NULL, &oid,
						SUMMARY_SHOW_AUTHOR_DATE);
			return res;
		}
	}
	if (res == 1)
		return run_git_commit(msg_file, opts, flags);

	return res;
}

static int is_original_commit_empty(struct commit *commit)
{
	const struct object_id *ptree_oid;

	if (parse_commit(commit))
		return error(_("could not parse commit %s"),
			     oid_to_hex(&commit->object.oid));
	if (commit->parents) {
		struct commit *parent = commit->parents->item;
		if (parse_commit(parent))
			return error(_("could not parse parent commit %s"),
				oid_to_hex(&parent->object.oid));
		ptree_oid = get_commit_tree_oid(parent);
	} else {
		ptree_oid = the_hash_algo->empty_tree; /* commit is root */
	}

	return !oidcmp(ptree_oid, get_commit_tree_oid(commit));
}

/*
 * Do we run "git commit" with "--allow-empty"?
 */
static int allow_empty(struct replay_opts *opts, struct commit *commit)
{
	int index_unchanged, empty_commit;

	/*
	 * Three cases:
	 *
	 * (1) we do not allow empty at all and error out.
	 *
	 * (2) we allow ones that were initially empty, but
	 * forbid the ones that become empty;
	 *
	 * (3) we allow both.
	 */
	if (!opts->allow_empty)
		return 0; /* let "git commit" barf as necessary */

	index_unchanged = is_index_unchanged();
	if (index_unchanged < 0)
		return index_unchanged;
	if (!index_unchanged)
		return 0; /* we do not have to say --allow-empty */

	if (opts->keep_redundant_commits)
		return 1;

	empty_commit = is_original_commit_empty(commit);
	if (empty_commit < 0)
		return empty_commit;
	if (!empty_commit)
		return 0;
	else
		return 1;
}

/*
 * Note that ordering matters in this enum. Not only must it match the mapping
 * below, it is also divided into several sections that matter.  When adding
 * new commands, make sure you add it in the right section.
 */
enum todo_command {
	/* commands that handle commits */
	TODO_PICK = 0,
	TODO_REVERT,
	TODO_EDIT,
	TODO_REWORD,
	TODO_FIXUP,
	TODO_SQUASH,
	/* commands that do something else than handling a single commit */
	TODO_EXEC,
	TODO_LABEL,
	TODO_RESET,
	TODO_MERGE,
	/* commands that do nothing but are counted for reporting progress */
	TODO_NOOP,
	TODO_DROP,
	/* comments (not counted for reporting progress) */
	TODO_COMMENT
};

static struct {
	char c;
	const char *str;
} todo_command_info[] = {
	{ 'p', "pick" },
	{ 0,   "revert" },
	{ 'e', "edit" },
	{ 'r', "reword" },
	{ 'f', "fixup" },
	{ 's', "squash" },
	{ 'x', "exec" },
	{ 'l', "label" },
	{ 't', "reset" },
	{ 'm', "merge" },
	{ 0,   "noop" },
	{ 'd', "drop" },
	{ 0,   NULL }
};

static const char *command_to_string(const enum todo_command command)
{
	if (command < TODO_COMMENT)
		return todo_command_info[command].str;
	die("Unknown command: %d", command);
}

static char command_to_char(const enum todo_command command)
{
	if (command < TODO_COMMENT && todo_command_info[command].c)
		return todo_command_info[command].c;
	return comment_line_char;
}

static int is_noop(const enum todo_command command)
{
	return TODO_NOOP <= command;
}

static int is_fixup(enum todo_command command)
{
	return command == TODO_FIXUP || command == TODO_SQUASH;
}

/* Does this command create a (non-merge) commit? */
static int is_pick_or_similar(enum todo_command command)
{
	switch (command) {
	case TODO_PICK:
	case TODO_REVERT:
	case TODO_EDIT:
	case TODO_REWORD:
	case TODO_FIXUP:
	case TODO_SQUASH:
		return 1;
	default:
		return 0;
	}
}

static int update_squash_messages(enum todo_command command,
		struct commit *commit, struct replay_opts *opts)
{
	struct strbuf buf = STRBUF_INIT;
	int res;
	const char *message, *body;

	if (opts->current_fixup_count > 0) {
		struct strbuf header = STRBUF_INIT;
		char *eol;

		if (strbuf_read_file(&buf, rebase_path_squash_msg(), 9) <= 0)
			return error(_("could not read '%s'"),
				rebase_path_squash_msg());

		eol = buf.buf[0] != comment_line_char ?
			buf.buf : strchrnul(buf.buf, '\n');

		strbuf_addf(&header, "%c ", comment_line_char);
		strbuf_addf(&header, _("This is a combination of %d commits."),
			    opts->current_fixup_count + 2);
		strbuf_splice(&buf, 0, eol - buf.buf, header.buf, header.len);
		strbuf_release(&header);
	} else {
		struct object_id head;
		struct commit *head_commit;
		const char *head_message, *body;

		if (get_oid("HEAD", &head))
			return error(_("need a HEAD to fixup"));
		if (!(head_commit = lookup_commit_reference(&head)))
			return error(_("could not read HEAD"));
		if (!(head_message = get_commit_buffer(head_commit, NULL)))
			return error(_("could not read HEAD's commit message"));

		find_commit_subject(head_message, &body);
		if (write_message(body, strlen(body),
				  rebase_path_fixup_msg(), 0)) {
			unuse_commit_buffer(head_commit, head_message);
			return error(_("cannot write '%s'"),
				     rebase_path_fixup_msg());
		}

		strbuf_addf(&buf, "%c ", comment_line_char);
		strbuf_addf(&buf, _("This is a combination of %d commits."), 2);
		strbuf_addf(&buf, "\n%c ", comment_line_char);
		strbuf_addstr(&buf, _("This is the 1st commit message:"));
		strbuf_addstr(&buf, "\n\n");
		strbuf_addstr(&buf, body);

		unuse_commit_buffer(head_commit, head_message);
	}

	if (!(message = get_commit_buffer(commit, NULL)))
		return error(_("could not read commit message of %s"),
			     oid_to_hex(&commit->object.oid));
	find_commit_subject(message, &body);

	if (command == TODO_SQUASH) {
		unlink(rebase_path_fixup_msg());
		strbuf_addf(&buf, "\n%c ", comment_line_char);
		strbuf_addf(&buf, _("This is the commit message #%d:"),
			    ++opts->current_fixup_count);
		strbuf_addstr(&buf, "\n\n");
		strbuf_addstr(&buf, body);
	} else if (command == TODO_FIXUP) {
		strbuf_addf(&buf, "\n%c ", comment_line_char);
		strbuf_addf(&buf, _("The commit message #%d will be skipped:"),
			    ++opts->current_fixup_count);
		strbuf_addstr(&buf, "\n\n");
		strbuf_add_commented_lines(&buf, body, strlen(body));
	} else
		return error(_("unknown command: %d"), command);
	unuse_commit_buffer(commit, message);

	res = write_message(buf.buf, buf.len, rebase_path_squash_msg(), 0);
	strbuf_release(&buf);

	if (!res) {
		strbuf_addf(&opts->current_fixups, "%s%s %s",
			    opts->current_fixups.len ? "\n" : "",
			    command_to_string(command),
			    oid_to_hex(&commit->object.oid));
		res = write_message(opts->current_fixups.buf,
				    opts->current_fixups.len,
				    rebase_path_current_fixups(), 0);
	}

	return res;
}

static void flush_rewritten_pending(void) {
	struct strbuf buf = STRBUF_INIT;
	struct object_id newoid;
	FILE *out;

	if (strbuf_read_file(&buf, rebase_path_rewritten_pending(), (GIT_MAX_HEXSZ + 1) * 2) > 0 &&
	    !get_oid("HEAD", &newoid) &&
	    (out = fopen_or_warn(rebase_path_rewritten_list(), "a"))) {
		char *bol = buf.buf, *eol;

		while (*bol) {
			eol = strchrnul(bol, '\n');
			fprintf(out, "%.*s %s\n", (int)(eol - bol),
					bol, oid_to_hex(&newoid));
			if (!*eol)
				break;
			bol = eol + 1;
		}
		fclose(out);
		unlink(rebase_path_rewritten_pending());
	}
	strbuf_release(&buf);
}

static void record_in_rewritten(struct object_id *oid,
		enum todo_command next_command) {
	FILE *out = fopen_or_warn(rebase_path_rewritten_pending(), "a");

	if (!out)
		return;

	fprintf(out, "%s\n", oid_to_hex(oid));
	fclose(out);

	if (!is_fixup(next_command))
		flush_rewritten_pending();
}

static int do_pick_commit(enum todo_command command, struct commit *commit,
		struct replay_opts *opts, int final_fixup)
{
	unsigned int flags = opts->edit ? EDIT_MSG : 0;
	const char *msg_file = opts->edit ? NULL : git_path_merge_msg(the_repository);
	struct object_id head;
	struct commit *base, *next, *parent;
	const char *base_label, *next_label;
	char *author = NULL;
	struct commit_message msg = { NULL, NULL, NULL, NULL };
	struct strbuf msgbuf = STRBUF_INIT;
	int res, unborn = 0, allow;

	if (opts->no_commit) {
		/*
		 * We do not intend to commit immediately.  We just want to
		 * merge the differences in, so let's compute the tree
		 * that represents the "current" state for merge-recursive
		 * to work on.
		 */
		if (write_cache_as_tree(&head, 0, NULL))
			return error(_("your index file is unmerged."));
	} else {
		unborn = get_oid("HEAD", &head);
		/* Do we want to generate a root commit? */
		if (is_pick_or_similar(command) && opts->have_squash_onto &&
		    !oidcmp(&head, &opts->squash_onto)) {
			if (is_fixup(command))
				return error(_("cannot fixup root commit"));
			flags |= CREATE_ROOT_COMMIT;
			unborn = 1;
		} else if (unborn)
			oidcpy(&head, the_hash_algo->empty_tree);
		if (index_differs_from(unborn ? empty_tree_oid_hex() : "HEAD",
				       NULL, 0))
			return error_dirty_index(opts);
	}
	discard_cache();

	if (!commit->parents)
		parent = NULL;
	else if (commit->parents->next) {
		/* Reverting or cherry-picking a merge commit */
		int cnt;
		struct commit_list *p;

		if (!opts->mainline)
			return error(_("commit %s is a merge but no -m option was given."),
				oid_to_hex(&commit->object.oid));

		for (cnt = 1, p = commit->parents;
		     cnt != opts->mainline && p;
		     cnt++)
			p = p->next;
		if (cnt != opts->mainline || !p)
			return error(_("commit %s does not have parent %d"),
				oid_to_hex(&commit->object.oid), opts->mainline);
		parent = p->item;
	} else if (0 < opts->mainline)
		return error(_("mainline was specified but commit %s is not a merge."),
			oid_to_hex(&commit->object.oid));
	else
		parent = commit->parents->item;

	if (get_message(commit, &msg) != 0)
		return error(_("cannot get commit message for %s"),
			oid_to_hex(&commit->object.oid));

	if (opts->allow_ff && !is_fixup(command) &&
	    ((parent && !oidcmp(&parent->object.oid, &head)) ||
	     (!parent && unborn))) {
		if (is_rebase_i(opts))
			write_author_script(msg.message);
		res = fast_forward_to(&commit->object.oid, &head, unborn,
			opts);
		if (res || command != TODO_REWORD)
			goto leave;
		flags |= EDIT_MSG | AMEND_MSG | VERIFY_MSG;
		msg_file = NULL;
		goto fast_forward_edit;
	}
	if (parent && parse_commit(parent) < 0)
		/* TRANSLATORS: The first %s will be a "todo" command like
		   "revert" or "pick", the second %s a SHA1. */
		return error(_("%s: cannot parse parent commit %s"),
			command_to_string(command),
			oid_to_hex(&parent->object.oid));

	/*
	 * "commit" is an existing commit.  We would want to apply
	 * the difference it introduces since its first parent "prev"
	 * on top of the current HEAD if we are cherry-pick.  Or the
	 * reverse of it if we are revert.
	 */

	if (command == TODO_REVERT) {
		base = commit;
		base_label = msg.label;
		next = parent;
		next_label = msg.parent_label;
		strbuf_addstr(&msgbuf, "Revert \"");
		strbuf_addstr(&msgbuf, msg.subject);
		strbuf_addstr(&msgbuf, "\"\n\nThis reverts commit ");
		strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));

		if (commit->parents && commit->parents->next) {
			strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
			strbuf_addstr(&msgbuf, oid_to_hex(&parent->object.oid));
		}
		strbuf_addstr(&msgbuf, ".\n");
	} else {
		const char *p;

		base = parent;
		base_label = msg.parent_label;
		next = commit;
		next_label = msg.label;

		/* Append the commit log message to msgbuf. */
		if (find_commit_subject(msg.message, &p))
			strbuf_addstr(&msgbuf, p);

		if (opts->record_origin) {
			strbuf_complete_line(&msgbuf);
			if (!has_conforming_footer(&msgbuf, NULL, 0))
				strbuf_addch(&msgbuf, '\n');
			strbuf_addstr(&msgbuf, cherry_picked_prefix);
			strbuf_addstr(&msgbuf, oid_to_hex(&commit->object.oid));
			strbuf_addstr(&msgbuf, ")\n");
		}
		if (!is_fixup(command))
			author = get_author(msg.message);
	}

	if (command == TODO_REWORD)
		flags |= EDIT_MSG | VERIFY_MSG;
	else if (is_fixup(command)) {
		if (update_squash_messages(command, commit, opts))
			return -1;
		flags |= AMEND_MSG;
		if (!final_fixup)
			msg_file = rebase_path_squash_msg();
		else if (file_exists(rebase_path_fixup_msg())) {
			flags |= CLEANUP_MSG;
			msg_file = rebase_path_fixup_msg();
		} else {
			const char *dest = git_path_squash_msg(the_repository);
			unlink(dest);
			if (copy_file(dest, rebase_path_squash_msg(), 0666))
				return error(_("could not rename '%s' to '%s'"),
					     rebase_path_squash_msg(), dest);
			unlink(git_path_merge_msg(the_repository));
			msg_file = dest;
			flags |= EDIT_MSG;
		}
	}

	if (opts->signoff && !is_fixup(command))
		append_signoff(&msgbuf, 0, 0);

	if (is_rebase_i(opts) && write_author_script(msg.message) < 0)
		res = -1;
	else if (!opts->strategy || !strcmp(opts->strategy, "recursive") || command == TODO_REVERT) {
		res = do_recursive_merge(base, next, base_label, next_label,
					 &head, &msgbuf, opts);
		if (res < 0)
			goto leave;

		res |= write_message(msgbuf.buf, msgbuf.len,
				     git_path_merge_msg(the_repository), 0);
	} else {
		struct commit_list *common = NULL;
		struct commit_list *remotes = NULL;

		res = write_message(msgbuf.buf, msgbuf.len,
				    git_path_merge_msg(the_repository), 0);

		commit_list_insert(base, &common);
		commit_list_insert(next, &remotes);
		res |= try_merge_command(opts->strategy,
					 opts->xopts_nr, (const char **)opts->xopts,
					common, oid_to_hex(&head), remotes);
		free_commit_list(common);
		free_commit_list(remotes);
	}
	strbuf_release(&msgbuf);

	/*
	 * If the merge was clean or if it failed due to conflict, we write
	 * CHERRY_PICK_HEAD for the subsequent invocation of commit to use.
	 * However, if the merge did not even start, then we don't want to
	 * write it at all.
	 */
	if (command == TODO_PICK && !opts->no_commit && (res == 0 || res == 1) &&
	    update_ref(NULL, "CHERRY_PICK_HEAD", &commit->object.oid, NULL,
		       REF_NO_DEREF, UPDATE_REFS_MSG_ON_ERR))
		res = -1;
	if (command == TODO_REVERT && ((opts->no_commit && res == 0) || res == 1) &&
	    update_ref(NULL, "REVERT_HEAD", &commit->object.oid, NULL,
		       REF_NO_DEREF, UPDATE_REFS_MSG_ON_ERR))
		res = -1;

	if (res) {
		error(command == TODO_REVERT
		      ? _("could not revert %s... %s")
		      : _("could not apply %s... %s"),
		      short_commit_name(commit), msg.subject);
		print_advice(res == 1, opts);
		rerere(opts->allow_rerere_auto);
		goto leave;
	}

	allow = allow_empty(opts, commit);
	if (allow < 0) {
		res = allow;
		goto leave;
	} else if (allow)
		flags |= ALLOW_EMPTY;
	if (!opts->no_commit) {
fast_forward_edit:
		if (author || command == TODO_REVERT || (flags & AMEND_MSG))
			res = do_commit(msg_file, author, opts, flags);
		else
			res = error(_("unable to parse commit author"));
	}

	if (!res && final_fixup) {
		unlink(rebase_path_fixup_msg());
		unlink(rebase_path_squash_msg());
		unlink(rebase_path_current_fixups());
		strbuf_reset(&opts->current_fixups);
		opts->current_fixup_count = 0;
	}

leave:
	free_message(commit, &msg);
	free(author);
	update_abort_safety_file();

	return res;
}

static int prepare_revs(struct replay_opts *opts)
{
	/*
	 * picking (but not reverting) ranges (but not individual revisions)
	 * should be done in reverse
	 */
	if (opts->action == REPLAY_PICK && !opts->revs->no_walk)
		opts->revs->reverse ^= 1;

	if (prepare_revision_walk(opts->revs))
		return error(_("revision walk setup failed"));

	if (!opts->revs->commits)
		return error(_("empty commit set passed"));
	return 0;
}

static int read_and_refresh_cache(struct replay_opts *opts)
{
	struct lock_file index_lock = LOCK_INIT;
	int index_fd = hold_locked_index(&index_lock, 0);
	if (read_index_preload(&the_index, NULL) < 0) {
		rollback_lock_file(&index_lock);
		return error(_("git %s: failed to read the index"),
			_(action_name(opts)));
	}
	refresh_index(&the_index, REFRESH_QUIET|REFRESH_UNMERGED, NULL, NULL, NULL);
	if (index_fd >= 0) {
		if (write_locked_index(&the_index, &index_lock,
				       COMMIT_LOCK | SKIP_IF_UNCHANGED)) {
			return error(_("git %s: failed to refresh the index"),
				_(action_name(opts)));
		}
	}
	return 0;
}

enum todo_item_flags {
	TODO_EDIT_MERGE_MSG = 1
};

struct todo_item {
	enum todo_command command;
	struct commit *commit;
	unsigned int flags;
	const char *arg;
	int arg_len;
	size_t offset_in_buf;
};

struct todo_list {
	struct strbuf buf;
	struct todo_item *items;
	int nr, alloc, current;
	int done_nr, total_nr;
	struct stat_data stat;
};

#define TODO_LIST_INIT { STRBUF_INIT }

static void todo_list_release(struct todo_list *todo_list)
{
	strbuf_release(&todo_list->buf);
	FREE_AND_NULL(todo_list->items);
	todo_list->nr = todo_list->alloc = 0;
}

static struct todo_item *append_new_todo(struct todo_list *todo_list)
{
	ALLOC_GROW(todo_list->items, todo_list->nr + 1, todo_list->alloc);
	return todo_list->items + todo_list->nr++;
}

static int parse_insn_line(struct todo_item *item, const char *bol, char *eol)
{
	struct object_id commit_oid;
	char *end_of_object_name;
	int i, saved, status, padding;

	item->flags = 0;

	/* left-trim */
	bol += strspn(bol, " \t");

	if (bol == eol || *bol == '\r' || *bol == comment_line_char) {
		item->command = TODO_COMMENT;
		item->commit = NULL;
		item->arg = bol;
		item->arg_len = eol - bol;
		return 0;
	}

	for (i = 0; i < TODO_COMMENT; i++)
		if (skip_prefix(bol, todo_command_info[i].str, &bol)) {
			item->command = i;
			break;
		} else if (bol[1] == ' ' && *bol == todo_command_info[i].c) {
			bol++;
			item->command = i;
			break;
		}
	if (i >= TODO_COMMENT)
		return -1;

	/* Eat up extra spaces/ tabs before object name */
	padding = strspn(bol, " \t");
	bol += padding;

	if (item->command == TODO_NOOP) {
		if (bol != eol)
			return error(_("%s does not accept arguments: '%s'"),
				     command_to_string(item->command), bol);
		item->commit = NULL;
		item->arg = bol;
		item->arg_len = eol - bol;
		return 0;
	}

	if (!padding)
		return error(_("missing arguments for %s"),
			     command_to_string(item->command));

	if (item->command == TODO_EXEC || item->command == TODO_LABEL ||
	    item->command == TODO_RESET) {
		item->commit = NULL;
		item->arg = bol;
		item->arg_len = (int)(eol - bol);
		return 0;
	}

	if (item->command == TODO_MERGE) {
		if (skip_prefix(bol, "-C", &bol))
			bol += strspn(bol, " \t");
		else if (skip_prefix(bol, "-c", &bol)) {
			bol += strspn(bol, " \t");
			item->flags |= TODO_EDIT_MERGE_MSG;
		} else {
			item->flags |= TODO_EDIT_MERGE_MSG;
			item->commit = NULL;
			item->arg = bol;
			item->arg_len = (int)(eol - bol);
			return 0;
		}
	}

	end_of_object_name = (char *) bol + strcspn(bol, " \t\n");
	saved = *end_of_object_name;
	*end_of_object_name = '\0';
	status = get_oid(bol, &commit_oid);
	*end_of_object_name = saved;

	item->arg = end_of_object_name + strspn(end_of_object_name, " \t");
	item->arg_len = (int)(eol - item->arg);

	if (status < 0)
		return -1;

	item->commit = lookup_commit_reference(&commit_oid);
	return !item->commit;
}

static int parse_insn_buffer(char *buf, struct todo_list *todo_list)
{
	struct todo_item *item;
	char *p = buf, *next_p;
	int i, res = 0, fixup_okay = file_exists(rebase_path_done());

	for (i = 1; *p; i++, p = next_p) {
		char *eol = strchrnul(p, '\n');

		next_p = *eol ? eol + 1 /* skip LF */ : eol;

		if (p != eol && eol[-1] == '\r')
			eol--; /* strip Carriage Return */

		item = append_new_todo(todo_list);
		item->offset_in_buf = p - todo_list->buf.buf;
		if (parse_insn_line(item, p, eol)) {
			res = error(_("invalid line %d: %.*s"),
				i, (int)(eol - p), p);
			item->command = TODO_NOOP;
		}

		if (fixup_okay)
			; /* do nothing */
		else if (is_fixup(item->command))
			return error(_("cannot '%s' without a previous commit"),
				command_to_string(item->command));
		else if (!is_noop(item->command))
			fixup_okay = 1;
	}

	return res;
}

static int count_commands(struct todo_list *todo_list)
{
	int count = 0, i;

	for (i = 0; i < todo_list->nr; i++)
		if (todo_list->items[i].command != TODO_COMMENT)
			count++;

	return count;
}

static int get_item_line_offset(struct todo_list *todo_list, int index)
{
	return index < todo_list->nr ?
		todo_list->items[index].offset_in_buf : todo_list->buf.len;
}

static const char *get_item_line(struct todo_list *todo_list, int index)
{
	return todo_list->buf.buf + get_item_line_offset(todo_list, index);
}

static int get_item_line_length(struct todo_list *todo_list, int index)
{
	return get_item_line_offset(todo_list, index + 1)
		-  get_item_line_offset(todo_list, index);
}

static ssize_t strbuf_read_file_or_whine(struct strbuf *sb, const char *path)
{
	int fd;
	ssize_t len;

	fd = open(path, O_RDONLY);
	if (fd < 0)
		return error_errno(_("could not open '%s'"), path);
	len = strbuf_read(sb, fd, 0);
	close(fd);
	if (len < 0)
		return error(_("could not read '%s'."), path);
	return len;
}

static int read_populate_todo(struct todo_list *todo_list,
			struct replay_opts *opts)
{
	struct stat st;
	const char *todo_file = get_todo_path(opts);
	int res;

	strbuf_reset(&todo_list->buf);
	if (strbuf_read_file_or_whine(&todo_list->buf, todo_file) < 0)
		return -1;

	res = stat(todo_file, &st);
	if (res)
		return error(_("could not stat '%s'"), todo_file);
	fill_stat_data(&todo_list->stat, &st);

	res = parse_insn_buffer(todo_list->buf.buf, todo_list);
	if (res) {
		if (is_rebase_i(opts))
			return error(_("please fix this using "
				       "'git rebase --edit-todo'."));
		return error(_("unusable instruction sheet: '%s'"), todo_file);
	}

	if (!todo_list->nr &&
	    (!is_rebase_i(opts) || !file_exists(rebase_path_done())))
		return error(_("no commits parsed."));

	if (!is_rebase_i(opts)) {
		enum todo_command valid =
			opts->action == REPLAY_PICK ? TODO_PICK : TODO_REVERT;
		int i;

		for (i = 0; i < todo_list->nr; i++)
			if (valid == todo_list->items[i].command)
				continue;
			else if (valid == TODO_PICK)
				return error(_("cannot cherry-pick during a revert."));
			else
				return error(_("cannot revert during a cherry-pick."));
	}

	if (is_rebase_i(opts)) {
		struct todo_list done = TODO_LIST_INIT;
		FILE *f = fopen_or_warn(rebase_path_msgtotal(), "w");

		if (strbuf_read_file(&done.buf, rebase_path_done(), 0) > 0 &&
				!parse_insn_buffer(done.buf.buf, &done))
			todo_list->done_nr = count_commands(&done);
		else
			todo_list->done_nr = 0;

		todo_list->total_nr = todo_list->done_nr
			+ count_commands(todo_list);
		todo_list_release(&done);

		if (f) {
			fprintf(f, "%d\n", todo_list->total_nr);
			fclose(f);
		}
	}

	return 0;
}

static int git_config_string_dup(char **dest,
				 const char *var, const char *value)
{
	if (!value)
		return config_error_nonbool(var);
	free(*dest);
	*dest = xstrdup(value);
	return 0;
}

static int populate_opts_cb(const char *key, const char *value, void *data)
{
	struct replay_opts *opts = data;
	int error_flag = 1;

	if (!value)
		error_flag = 0;
	else if (!strcmp(key, "options.no-commit"))
		opts->no_commit = git_config_bool_or_int(key, value, &error_flag);
	else if (!strcmp(key, "options.edit"))
		opts->edit = git_config_bool_or_int(key, value, &error_flag);
	else if (!strcmp(key, "options.signoff"))
		opts->signoff = git_config_bool_or_int(key, value, &error_flag);
	else if (!strcmp(key, "options.record-origin"))
		opts->record_origin = git_config_bool_or_int(key, value, &error_flag);
	else if (!strcmp(key, "options.allow-ff"))
		opts->allow_ff = git_config_bool_or_int(key, value, &error_flag);
	else if (!strcmp(key, "options.mainline"))
		opts->mainline = git_config_int(key, value);
	else if (!strcmp(key, "options.strategy"))
		git_config_string_dup(&opts->strategy, key, value);
	else if (!strcmp(key, "options.gpg-sign"))
		git_config_string_dup(&opts->gpg_sign, key, value);
	else if (!strcmp(key, "options.strategy-option")) {
		ALLOC_GROW(opts->xopts, opts->xopts_nr + 1, opts->xopts_alloc);
		opts->xopts[opts->xopts_nr++] = xstrdup(value);
	} else if (!strcmp(key, "options.allow-rerere-auto"))
		opts->allow_rerere_auto =
			git_config_bool_or_int(key, value, &error_flag) ?
				RERERE_AUTOUPDATE : RERERE_NOAUTOUPDATE;
	else
		return error(_("invalid key: %s"), key);

	if (!error_flag)
		return error(_("invalid value for %s: %s"), key, value);

	return 0;
}

static void read_strategy_opts(struct replay_opts *opts, struct strbuf *buf)
{
	int i;

	strbuf_reset(buf);
	if (!read_oneliner(buf, rebase_path_strategy(), 0))
		return;
	opts->strategy = strbuf_detach(buf, NULL);
	if (!read_oneliner(buf, rebase_path_strategy_opts(), 0))
		return;

	opts->xopts_nr = split_cmdline(buf->buf, (const char ***)&opts->xopts);
	for (i = 0; i < opts->xopts_nr; i++) {
		const char *arg = opts->xopts[i];

		skip_prefix(arg, "--", &arg);
		opts->xopts[i] = xstrdup(arg);
	}
}

static int read_populate_opts(struct replay_opts *opts)
{
	if (is_rebase_i(opts)) {
		struct strbuf buf = STRBUF_INIT;

		if (read_oneliner(&buf, rebase_path_gpg_sign_opt(), 1)) {
			if (!starts_with(buf.buf, "-S"))
				strbuf_reset(&buf);
			else {
				free(opts->gpg_sign);
				opts->gpg_sign = xstrdup(buf.buf + 2);
			}
			strbuf_reset(&buf);
		}

		if (read_oneliner(&buf, rebase_path_allow_rerere_autoupdate(), 1)) {
			if (!strcmp(buf.buf, "--rerere-autoupdate"))
				opts->allow_rerere_auto = RERERE_AUTOUPDATE;
			else if (!strcmp(buf.buf, "--no-rerere-autoupdate"))
				opts->allow_rerere_auto = RERERE_NOAUTOUPDATE;
			strbuf_reset(&buf);
		}

		if (file_exists(rebase_path_verbose()))
			opts->verbose = 1;

		if (file_exists(rebase_path_signoff())) {
			opts->allow_ff = 0;
			opts->signoff = 1;
		}

		read_strategy_opts(opts, &buf);
		strbuf_release(&buf);

		if (read_oneliner(&opts->current_fixups,
				  rebase_path_current_fixups(), 1)) {
			const char *p = opts->current_fixups.buf;
			opts->current_fixup_count = 1;
			while ((p = strchr(p, '\n'))) {
				opts->current_fixup_count++;
				p++;
			}
		}

		if (read_oneliner(&buf, rebase_path_squash_onto(), 0)) {
			if (get_oid_hex(buf.buf, &opts->squash_onto) < 0)
				return error(_("unusable squash-onto"));
			opts->have_squash_onto = 1;
		}

		return 0;
	}

	if (!file_exists(git_path_opts_file()))
		return 0;
	/*
	 * The function git_parse_source(), called from git_config_from_file(),
	 * may die() in case of a syntactically incorrect file. We do not care
	 * about this case, though, because we wrote that file ourselves, so we
	 * are pretty certain that it is syntactically correct.
	 */
	if (git_config_from_file(populate_opts_cb, git_path_opts_file(), opts) < 0)
		return error(_("malformed options sheet: '%s'"),
			git_path_opts_file());
	return 0;
}

static int walk_revs_populate_todo(struct todo_list *todo_list,
				struct replay_opts *opts)
{
	enum todo_command command = opts->action == REPLAY_PICK ?
		TODO_PICK : TODO_REVERT;
	const char *command_string = todo_command_info[command].str;
	struct commit *commit;

	if (prepare_revs(opts))
		return -1;

	while ((commit = get_revision(opts->revs))) {
		struct todo_item *item = append_new_todo(todo_list);
		const char *commit_buffer = get_commit_buffer(commit, NULL);
		const char *subject;
		int subject_len;

		item->command = command;
		item->commit = commit;
		item->arg = NULL;
		item->arg_len = 0;
		item->offset_in_buf = todo_list->buf.len;
		subject_len = find_commit_subject(commit_buffer, &subject);
		strbuf_addf(&todo_list->buf, "%s %s %.*s\n", command_string,
			short_commit_name(commit), subject_len, subject);
		unuse_commit_buffer(commit, commit_buffer);
	}
	return 0;
}

static int create_seq_dir(void)
{
	if (file_exists(git_path_seq_dir())) {
		error(_("a cherry-pick or revert is already in progress"));
		advise(_("try \"git cherry-pick (--continue | --quit | --abort)\""));
		return -1;
	} else if (mkdir(git_path_seq_dir(), 0777) < 0)
		return error_errno(_("could not create sequencer directory '%s'"),
				   git_path_seq_dir());
	return 0;
}

static int save_head(const char *head)
{
	struct lock_file head_lock = LOCK_INIT;
	struct strbuf buf = STRBUF_INIT;
	int fd;
	ssize_t written;

	fd = hold_lock_file_for_update(&head_lock, git_path_head_file(), 0);
	if (fd < 0)
		return error_errno(_("could not lock HEAD"));
	strbuf_addf(&buf, "%s\n", head);
	written = write_in_full(fd, buf.buf, buf.len);
	strbuf_release(&buf);
	if (written < 0) {
		error_errno(_("could not write to '%s'"), git_path_head_file());
		rollback_lock_file(&head_lock);
		return -1;
	}
	if (commit_lock_file(&head_lock) < 0)
		return error(_("failed to finalize '%s'"), git_path_head_file());
	return 0;
}

static int rollback_is_safe(void)
{
	struct strbuf sb = STRBUF_INIT;
	struct object_id expected_head, actual_head;

	if (strbuf_read_f