sequencer.c

#include "git-compat-util.h"
#include "abspath.h"
#include "advice.h"
#include "config.h"
#include "copy.h"
#include "environment.h"
#include "gettext.h"
#include "hex.h"
#include "lockfile.h"
#include "dir.h"
#include "object-file.h"
#include "object-name.h"
#include "object-store-ll.h"
#include "object.h"
#include "pager.h"
#include "commit.h"
#include "sequencer.h"
#include "run-command.h"
#include "hook.h"
#include "utf8.h"
#include "cache-tree.h"
#include "diff.h"
#include "path.h"
#include "revision.h"
#include "rerere.h"
#include "merge.h"
#include "merge-ort.h"
#include "merge-ort-wrappers.h"
#include "refs.h"
#include "sparse-index.h"
#include "strvec.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 "oidmap.h"
#include "oidset.h"
#include "commit-slab.h"
#include "alias.h"
#include "commit-reach.h"
#include "rebase-interactive.h"
#include "reset.h"
#include "branch.h"

#define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"

/*
 * To accommodate common filesystem limitations, where the loose refs' file
 * names must not exceed `NAME_MAX`, the labels generated by `git rebase
 * --rebase-merges` need to be truncated if the corresponding commit subjects
 * are too long.
 * Add some margin to stay clear from reaching `NAME_MAX`.
 */
#define GIT_MAX_LABEL_LENGTH ((NAME_MAX) - (LOCK_SUFFIX_LEN) - 16)

static 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")

static 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'.
 */
GIT_PATH_FUNC(rebase_path_todo, "rebase-merge/git-rebase-todo")
GIT_PATH_FUNC(rebase_path_todo_backup, "rebase-merge/git-rebase-todo.backup")

GIT_PATH_FUNC(rebase_path_dropped, "rebase-merge/dropped")

/*
 * 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 commit object name of the corresponding patch.
 */
static GIT_PATH_FUNC(rebase_path_stopped_sha, "rebase-merge/stopped-sha")
/*
 * When we stop for the user to resolve conflicts this file contains
 * the patch of the commit that is being picked.
 */
static GIT_PATH_FUNC(rebase_path_patch, "rebase-merge/patch")
/*
 * 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 containing 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 update-refs file stores a list of refs that will be updated at the end
 * of the rebase sequence. The 'update-ref <ref>' commands in the todo file
 * update the OIDs for the refs in this file, but the refs are not updated
 * until the end of the rebase sequence.
 *
 * rebase_path_update_refs() returns the path to this file for a given
 * worktree directory. For the current worktree, pass the_repository->gitdir.
 */
static char *rebase_path_update_refs(const char *wt_git_dir)
{
	return xstrfmt("%s/rebase-merge/update-refs", wt_git_dir);
}

/*
 * The following files are written by git-rebase just after parsing the
 * command-line.
 */
static GIT_PATH_FUNC(rebase_path_gpg_sign_opt, "rebase-merge/gpg_sign_opt")
static GIT_PATH_FUNC(rebase_path_cdate_is_adate, "rebase-merge/cdate_is_adate")
static GIT_PATH_FUNC(rebase_path_ignore_date, "rebase-merge/ignore_date")
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_quiet, "rebase-merge/quiet")
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 GIT_PATH_FUNC(rebase_path_reschedule_failed_exec, "rebase-merge/reschedule-failed-exec")
static GIT_PATH_FUNC(rebase_path_no_reschedule_failed_exec, "rebase-merge/no-reschedule-failed-exec")
static GIT_PATH_FUNC(rebase_path_drop_redundant_commits, "rebase-merge/drop_redundant_commits")
static GIT_PATH_FUNC(rebase_path_keep_redundant_commits, "rebase-merge/keep_redundant_commits")

/**
 * A 'struct update_refs_record' represents a value in the update-refs
 * list. We use a string_list to map refs to these (before, after) pairs.
 */
struct update_ref_record {
	struct object_id before;
	struct object_id after;
};

static struct update_ref_record *init_update_ref_record(const char *ref)
{
	struct update_ref_record *rec;

	CALLOC_ARRAY(rec, 1);

	oidcpy(&rec->before, null_oid());
	oidcpy(&rec->after, null_oid());

	/* This may fail, but that's fine, we will keep the null OID. */
	read_ref(ref, &rec->before);

	return rec;
}

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

	if (!strcmp(k, "commit.cleanup")) {
		if (!v)
			return config_error_nonbool(k);

		if (!strcmp(v, "verbatim")) {
			opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_NONE;
			opts->explicit_cleanup = 1;
		} else if (!strcmp(v, "whitespace")) {
			opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_SPACE;
			opts->explicit_cleanup = 1;
		} else if (!strcmp(v, "strip")) {
			opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_ALL;
			opts->explicit_cleanup = 1;
		} else if (!strcmp(v, "scissors")) {
			opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_SCISSORS;
			opts->explicit_cleanup = 1;
		} else {
			warning(_("invalid commit message cleanup mode '%s'"),
				  v);
		}

		return 0;
	}

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

	if (!opts->default_strategy && !strcmp(k, "pull.twohead")) {
		int ret = git_config_string((const char**)&opts->default_strategy, k, v);
		if (ret == 0) {
			/*
			 * pull.twohead is allowed to be multi-valued; we only
			 * care about the first value.
			 */
			char *tmp = strchr(opts->default_strategy, ' ');
			if (tmp)
				*tmp = '\0';
		}
		return ret;
	}

	if (opts->action == REPLAY_REVERT && !strcmp(k, "revert.reference"))
		opts->commit_use_reference = git_config_bool(k, v);

	return git_diff_basic_config(k, v, ctx, 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,
	size_t ignore_footer)
{
	struct process_trailer_options opts = PROCESS_TRAILER_OPTIONS_INIT;
	struct trailer_info info;
	size_t i;
	int found_sob = 0, found_sob_last = 0;
	char saved_char;

	opts.no_divider = 1;

	if (ignore_footer) {
		saved_char = sb->buf[sb->len - ignore_footer];
		sb->buf[sb->len - ignore_footer] = '\0';
	}

	trailer_info_get(&opts, sb->buf, &info);

	if (ignore_footer)
		sb->buf[sb->len - ignore_footer] = saved_char;

	if (info.trailer_block_start == info.trailer_block_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;
}

void replay_opts_release(struct replay_opts *opts)
{
	free(opts->gpg_sign);
	free(opts->reflog_action);
	free(opts->default_strategy);
	free(opts->strategy);
	strvec_clear (&opts->xopts);
	strbuf_release(&opts->current_fixups);
	if (opts->revs)
		release_revisions(opts->revs);
	free(opts->revs);
}

int sequencer_remove_state(struct replay_opts *opts)
{
	struct strbuf buf = STRBUF_INIT;
	int ret = 0;

	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) cleanup", p, NULL, 0) < 0) {
				warning(_("could not delete '%s'"), p);
				ret = -1;
			}
			if (!eol)
				break;
			p = eol + 1;
		}
	}

	strbuf_reset(&buf);
	strbuf_addstr(&buf, get_dir(opts));
	if (remove_dir_recursively(&buf, 0))
		ret = error(_("could not remove '%s'"), buf.buf);
	strbuf_release(&buf);

	return ret;
}

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");
	}
	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 repository *r, struct commit *commit)
{
	return repo_find_unique_abbrev(r, &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 = repo_logmsg_reencode(the_repository, commit, NULL,
					    get_commit_output_encoding());
	abbrev = short_commit_name(the_repository, 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);
	repo_unuse_commit_buffer(the_repository, commit, msg->message);
}

const char *rebase_resolvemsg =
N_("Resolve all conflicts manually, mark them as resolved with\n"
"\"git add/rm <conflicted_files>\", then run \"git rebase --continue\".\n"
"You can instead skip this commit: run \"git rebase --skip\".\n"
"To abort and get back to the state before \"git rebase\", run "
"\"git rebase --abort\".");

static void print_advice(struct repository *r, int show_hint,
			 struct replay_opts *opts)
{
	const char *msg;

	if (is_rebase_i(opts))
		msg = rebase_resolvemsg;
	else
		msg = getenv("GIT_CHERRY_PICK_HELP");

	if (msg) {
		advise_if_enabled(ADVICE_MERGE_CONFLICT, "%s", msg);
		/*
		 * A conflict has occurred but the porcelain
		 * (typically rebase --interactive) wants to take care
		 * of the commit itself so remove CHERRY_PICK_HEAD
		 */
		refs_delete_ref(get_main_ref_store(r), "", "CHERRY_PICK_HEAD",
				NULL, REF_NO_DEREF);
		return;
	}

	if (show_hint) {
		if (opts->no_commit)
			advise_if_enabled(ADVICE_MERGE_CONFLICT,
					  _("after resolving the conflicts, mark the corrected paths\n"
					    "with 'git add <paths>' or 'git rm <paths>'"));
		else if (opts->action == REPLAY_PICK)
			advise_if_enabled(ADVICE_MERGE_CONFLICT,
					  _("After resolving the conflicts, mark them with\n"
					    "\"git add/rm <pathspec>\", then run\n"
					    "\"git cherry-pick --continue\".\n"
					    "You can instead skip this commit with \"git cherry-pick --skip\".\n"
					    "To abort and get back to the state before \"git cherry-pick\",\n"
					    "run \"git cherry-pick --abort\"."));
		else if (opts->action == REPLAY_REVERT)
			advise_if_enabled(ADVICE_MERGE_CONFLICT,
					  _("After resolving the conflicts, mark them with\n"
					    "\"git add/rm <pathspec>\", then run\n"
					    "\"git revert --continue\".\n"
					    "You can instead skip this commit with \"git revert --skip\".\n"
					    "To abort and get back to the state before \"git revert\",\n"
					    "run \"git revert --abort\"."));
		else
			BUG("unexpected pick action in print_advice()");
	}
}

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;
}

int read_oneliner(struct strbuf *buf,
	const char *path, unsigned flags)
{
	int orig_len = buf->len;

	if (strbuf_read_file(buf, path, 0) < 0) {
		if ((flags & READ_ONELINER_WARN_MISSING) ||
		    (errno != ENOENT && errno != ENOTDIR))
			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 ((flags & READ_ONELINER_SKIP_IF_EMPTY) && buf->len == orig_len)
		return 0;

	return 1;
}

static struct tree *empty_tree(struct repository *r)
{
	return lookup_tree(r, the_hash_algo->empty_tree);
}

static int error_dirty_index(struct repository *repo, struct replay_opts *opts)
{
	if (repo_read_index_unmerged(repo))
		return error_resolve_conflict(action_name(opts));

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

	if (advice_enabled(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 (!repo_get_oid(the_repository, "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(struct repository *r,
			   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;

	repo_read_index(r);
	if (checkout_fast_forward(r, 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;
}

enum commit_msg_cleanup_mode get_cleanup_mode(const char *cleanup_arg,
	int use_editor)
{
	if (!cleanup_arg || !strcmp(cleanup_arg, "default"))
		return use_editor ? COMMIT_MSG_CLEANUP_ALL :
				    COMMIT_MSG_CLEANUP_SPACE;
	else if (!strcmp(cleanup_arg, "verbatim"))
		return COMMIT_MSG_CLEANUP_NONE;
	else if (!strcmp(cleanup_arg, "whitespace"))
		return COMMIT_MSG_CLEANUP_SPACE;
	else if (!strcmp(cleanup_arg, "strip"))
		return COMMIT_MSG_CLEANUP_ALL;
	else if (!strcmp(cleanup_arg, "scissors"))
		return use_editor ? COMMIT_MSG_CLEANUP_SCISSORS :
				    COMMIT_MSG_CLEANUP_SPACE;
	else
		die(_("Invalid cleanup mode %s"), cleanup_arg);
}

/*
 * NB using int rather than enum cleanup_mode to stop clang's
 * -Wtautological-constant-out-of-range-compare complaining that the comparison
 * is always true.
 */
static const char *describe_cleanup_mode(int cleanup_mode)
{
	static const char *modes[] = { "whitespace",
				       "verbatim",
				       "scissors",
				       "strip" };

	if (cleanup_mode < ARRAY_SIZE(modes))
		return modes[cleanup_mode];

	BUG("invalid cleanup_mode provided (%d)", cleanup_mode);
}

void append_conflicts_hint(struct index_state *istate,
	struct strbuf *msgbuf, enum commit_msg_cleanup_mode cleanup_mode)
{
	int i;

	if (cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS) {
		strbuf_addch(msgbuf, '\n');
		wt_status_append_cut_line(msgbuf);
		strbuf_addstr(msgbuf, comment_line_str);
	}

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

static int do_recursive_merge(struct repository *r,
			      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 merge_result result;
	struct tree *next_tree, *base_tree, *head_tree;
	int clean, show_output;
	int i;
	struct lock_file index_lock = LOCK_INIT;

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

	repo_read_index(r);

	init_merge_options(&o, r);
	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);
	if (!head_tree)
		return error(_("unable to read tree (%s)"), oid_to_hex(head));
	next_tree = next ? repo_get_commit_tree(r, next) : empty_tree(r);
	base_tree = base ? repo_get_commit_tree(r, base) : empty_tree(r);

	for (i = 0; i < opts->xopts.nr; i++)
		parse_merge_opt(&o, opts->xopts.v[i]);

	if (!opts->strategy || !strcmp(opts->strategy, "ort")) {
		memset(&result, 0, sizeof(result));
		merge_incore_nonrecursive(&o, base_tree, head_tree, next_tree,
					    &result);
		show_output = !is_rebase_i(opts) || !result.clean;
		/*
		 * TODO: merge_switch_to_result will update index/working tree;
		 * we only really want to do that if !result.clean || this is
		 * the final patch to be picked.  But determining this is the
		 * final patch would take some work, and "head_tree" would need
		 * to be replace with the tree the index matched before we
		 * started doing any picks.
		 */
		merge_switch_to_result(&o, head_tree, &result, 1, show_output);
		clean = result.clean;
	} else {
		ensure_full_index(r->index);
		clean = merge_trees(&o, head_tree, next_tree, base_tree);
		if (is_rebase_i(opts) && clean <= 0)
			fputs(o.obuf.buf, stdout);
		strbuf_release(&o.obuf);
	}
	if (clean < 0) {
		rollback_lock_file(&index_lock);
		return clean;
	}

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

	if (!clean)
		append_conflicts_hint(r->index, msgbuf,
				      opts->default_msg_cleanup);

	return !clean;
}

static struct object_id *get_cache_tree_oid(struct index_state *istate)
{
	if (!cache_tree_fully_valid(istate->cache_tree))
		if (cache_tree_update(istate, 0)) {
			error(_("unable to update cache tree"));
			return NULL;
		}

	return &istate->cache_tree->oid;
}

static int is_index_unchanged(struct repository *r)
{
	struct object_id head_oid, *cache_tree_oid;
	const struct object_id *head_tree_oid;
	struct commit *head_commit;
	struct index_state *istate = r->index;
	const char *head_name;

	if (!resolve_ref_unsafe("HEAD", RESOLVE_REF_READING, &head_oid, NULL)) {
		/* Check to see if this is an unborn branch */
		head_name = resolve_ref_unsafe("HEAD",
			RESOLVE_REF_READING | RESOLVE_REF_NO_RECURSE,
			&head_oid, NULL);
		if (!head_name ||
			!starts_with(head_name, "refs/heads/") ||
			!is_null_oid(&head_oid))
			return error(_("could not resolve HEAD commit"));
		head_tree_oid = the_hash_algo->empty_tree;
	} else {
		head_commit = lookup_commit(r, &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.  repo_parse_commit() will return failure
		 * without further complaints in such a case.  Otherwise, if
		 * the commit is invalid, repo_parse_commit() will complain.  So
		 * there is nothing for us to say here.  Just return failure.
		 */
		if (repo_parse_commit(r, head_commit))
			return -1;

		head_tree_oid = get_commit_tree_oid(head_commit);
	}

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

	return oideq(cache_tree_oid, head_tree_oid);
}

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++));
	strbuf_addch(&buf, '\'');
	res = write_message(buf.buf, buf.len, rebase_path_author_script(), 1);
	strbuf_release(&buf);
	return res;
}

/**
 * Take a series of KEY='VALUE' lines where VALUE part is
 * sq-quoted, and append <KEY, VALUE> at the end of the string list
 */
static int parse_key_value_squoted(char *buf, struct string_list *list)
{
	while (*buf) {
		struct string_list_item *item;
		char *np;
		char *cp = strchr(buf, '=');
		if (!cp) {
			np = strchrnul(buf, '\n');
			return error(_("no key present in '%.*s'"),
				     (int) (np - buf), buf);
		}
		np = strchrnul(cp, '\n');
		*cp++ = '\0';
		item = string_list_append(list, buf);

		buf = np + (*np == '\n');
		*np = '\0';
		cp = sq_dequote(cp);
		if (!cp)
			return error(_("unable to dequote value of '%s'"),
				     item->string);
		item->util = xstrdup(cp);
	}
	return 0;
}

/**
 * Reads and parses the state directory's "author-script" file, and sets name,
 * email and date accordingly.
 * Returns 0 on success, -1 if the file could not be parsed.
 *
 * The author script is of the format:
 *
 *	GIT_AUTHOR_NAME='$author_name'
 *	GIT_AUTHOR_EMAIL='$author_email'
 *	GIT_AUTHOR_DATE='$author_date'
 *
 * where $author_name, $author_email and $author_date are quoted. We are strict
 * with our parsing, as the file was meant to be eval'd in the now-removed
 * git-am.sh/git-rebase--interactive.sh scripts, and thus if the file differs
 * from what this function expects, it is better to bail out than to do
 * something that the user does not expect.
 */
int read_author_script(const char *path, char **name, char **email, char **date,
		       int allow_missing)
{
	struct strbuf buf = STRBUF_INIT;
	struct string_list kv = STRING_LIST_INIT_DUP;
	int retval = -1; /* assume failure */
	int i, name_i = -2, email_i = -2, date_i = -2, err = 0;

	if (strbuf_read_file(&buf, path, 256) <= 0) {
		strbuf_release(&buf);
		if (errno == ENOENT && allow_missing)
			return 0;
		else
			return error_errno(_("could not open '%s' for reading"),
					   path);
	}

	if (parse_key_value_squoted(buf.buf, &kv))
		goto finish;

	for (i = 0; i < kv.nr; i++) {
		if (!strcmp(kv.items[i].string, "GIT_AUTHOR_NAME")) {
			if (name_i != -2)
				name_i = error(_("'GIT_AUTHOR_NAME' already given"));
			else
				name_i = i;
		} else if (!strcmp(kv.items[i].string, "GIT_AUTHOR_EMAIL")) {
			if (email_i != -2)
				email_i = error(_("'GIT_AUTHOR_EMAIL' already given"));
			else
				email_i = i;
		} else if (!strcmp(kv.items[i].string, "GIT_AUTHOR_DATE")) {
			if (date_i != -2)
				date_i = error(_("'GIT_AUTHOR_DATE' already given"));
			else
				date_i = i;
		} else {
			err = error(_("unknown variable '%s'"),
				    kv.items[i].string);
		}
	}
	if (name_i == -2)
		error(_("missing 'GIT_AUTHOR_NAME'"));
	if (email_i == -2)
		error(_("missing 'GIT_AUTHOR_EMAIL'"));
	if (date_i == -2)
		error(_("missing 'GIT_AUTHOR_DATE'"));
	if (name_i < 0 || email_i < 0 || date_i < 0 || err)
		goto finish;
	*name = kv.items[name_i].util;
	*email = kv.items[email_i].util;
	*date = kv.items[date_i].util;
	retval = 0;
finish:
	string_list_clear(&kv, !!retval);
	strbuf_release(&buf);
	return retval;
}

/*
 * Read a GIT_AUTHOR_NAME, GIT_AUTHOR_EMAIL AND GIT_AUTHOR_DATE from a
 * file with shell quoting into struct strvec. Returns -1 on
 * error, 0 otherwise.
 */
static int read_env_script(struct strvec *env)
{
	char *name, *email, *date;

	if (read_author_script(rebase_path_author_script(),
			       &name, &email, &date, 0))
		return -1;

	strvec_pushf(env, "GIT_AUTHOR_NAME=%s", name);
	strvec_pushf(env, "GIT_AUTHOR_EMAIL=%s", email);
	strvec_pushf(env, "GIT_AUTHOR_DATE=%s", date);
	free(name);
	free(email);
	free(date);

	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;
}

static const char *author_date_from_env(const struct strvec *env)
{
	int i;
	const char *date;

	for (i = 0; i < env->nr; i++)
		if (skip_prefix(env->v[i],
				"GIT_AUTHOR_DATE=", &date))
			return date;
	/*
	 * If GIT_AUTHOR_DATE is missing we should have already errored out when
	 * reading the script
	 */
	BUG("GIT_AUTHOR_DATE missing from author script");
}

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)
#define VERBATIM_MSG (1<<6)

static int run_command_silent_on_success(struct child_process *cmd)
{
	struct strbuf buf = STRBUF_INIT;
	int rc;

	cmd->stdout_to_stderr = 1;
	rc = pipe_command(cmd,
			  NULL, 0,
			  NULL, 0,
			  &buf, 0);

	if (rc)
		fputs(buf.buf, stderr);
	strbuf_release(&buf);
	return rc;
}

/*
 * 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;

	if ((flags & CLEANUP_MSG) && (flags & VERBATIM_MSG))
		BUG("CLEANUP_MSG and VERBATIM_MSG are mutually exclusive");

	cmd.git_cmd = 1;

	if (is_rebase_i(opts) &&
	    ((opts->committer_date_is_author_date && !opts->ignore_date) ||
	     !(!defmsg && (flags & AMEND_MSG))) &&
	    read_env_script(&cmd.env)) {
		const char *gpg_opt = gpg_sign_opt_quoted(opts);

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

	strvec_pushf(&cmd.env, GIT_REFLOG_ACTION "=%s", opts->reflog_message);

	if (opts->committer_date_is_author_date)
		strvec_pushf(&cmd.env, "GIT_COMMITTER_DATE=%s",
			     opts->ignore_date ?
			     "" :
			     author_date_from_env(&cmd.env));
	if (opts->ignore_date)
		strvec_push(&cmd.env, "GIT_AUTHOR_DATE=");

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

	if (!(flags & VERIFY_MSG))
		strvec_push(&cmd.args, "-n");
	if ((flags & AMEND_MSG))
		strvec_push(&cmd.args, "--amend");
	if (opts->gpg_sign)
		strvec_pushf(&cmd.args, "-S%s", opts->gpg_sign);
	else
		strvec_push(&cmd.args, "--no-gpg-sign");
	if (defmsg)
		strvec_pushl(&cmd.args, "-F", defmsg, NULL);
	else if (!(flags & EDIT_MSG))
		strvec_pushl(&cmd.args, "-C", "HEAD", NULL);
	if ((flags & CLEANUP_MSG))
		strvec_push(&cmd.args, "--cleanup=strip");
	if ((flags & VERBATIM_MSG))
		strvec_push(&cmd.args, "--cleanup=verbatim");
	if ((flags & EDIT_MSG))
		strvec_push(&cmd.args, "-e");
	else if (!(flags & CLEANUP_MSG) &&
		 !opts->signoff && !opts->record_origin &&
		 !opts->explicit_cleanup)
		strvec_push(&cmd.args, "--cleanup=verbatim");

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

	if (!(flags & EDIT_MSG))
		strvec_push(&cmd.args, "--allow-empty-message");

	if (is_rebase_i(opts) && !(flags & EDIT_MSG))
		return run_command_silent_on_success(&cmd);
	else
		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;
}

void cleanup_message(struct strbuf *msgbuf,
	enum commit_msg_cleanup_mode cleanup_mode, int verbose)
{
	if (verbose || /* Truncate the message just before the diff, if any. */
	    cleanup_mode == COMMIT_MSG_CLEANUP_SCISSORS)
		strbuf_setlen(msgbuf, wt_status_locate_end(msgbuf->buf, msgbuf->len));
	if (cleanup_mode != COMMIT_MSG_CLEANUP_NONE)
		strbuf_stripspace(msgbuf,
		  cleanup_mode == COMMIT_MSG_CLEANUP_ALL ? comment_line_str : NULL);
}

/*
 * 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 ? comment_line_str : NULL);
	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;
	int code;
	struct strbuf sb = STRBUF_INIT;
	const char *hook_path = find_hook("post-rewrite");

	if (!hook_path)
		return 0;

	strvec_pushl(&proc.args, hook_path, "amend", NULL);
	proc.in = -1;
	proc.stdout_to_stderr = 1;
	proc.trace2_hook_name = "post-rewrite";

	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(struct repository *r,
			 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(r, cfg, "Notes added by 'git commit --amend'");
	}
	run_rewrite_hook(&old_head->object.oid, new_head);
}

static int run_prepare_commit_msg_hook(struct repository *r,
				       struct strbuf *msg,
				       const char *commit)
{
	int ret = 0;
	const char *name, *arg1 = NULL, *arg2 = NULL;

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

	if (commit) {
		arg1 = "commit";
		arg2 = commit;
	} else {
		arg1 = "message";
	}
	if (run_commit_hook(0, r->index_file, NULL, "prepare-commit-msg", name,
			    arg1, arg2, NULL))
		ret = error(_("'prepare-commit-msg' hook failed"));

	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 = interpolate_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(struct repository *r,
			  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;
	struct ref_store *refs;

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

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

	repo_format_commit_message(r, commit, "%an <%ae>", &author_ident,
				   &pctx);
	repo_format_commit_message(r, 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;

		repo_format_commit_message(r, 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_enabled(ADVICE_IMPLICIT_IDENTITY)) {
			strbuf_addch(&format, '\n');
			strbuf_addstr(&format, implicit_ident_advice());
		}
	}
	strbuf_release(&author_ident);
	strbuf_release(&committer_ident);

	repo_init_revisions(r, &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;
	diff_setup_done(&rev.diffopt);

	refs = get_main_ref_store(r);
	head = refs_resolve_ref_unsafe(refs, "HEAD", 0, NULL, NULL);
	if (!head)
		die(_("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);
	}

	release_revisions(&rev);
	strbuf_release(&format);
}

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

	if (repo_get_oid(r, "HEAD", &oid)) {
		current_head = NULL;
	} else {
		current_head = lookup_commit_reference(r, &oid);
		if (!current_head)
			return error(_("could not parse HEAD"));
		if (!oideq(&oid, &current_head->object.oid)) {
			warning(_("HEAD %s is not a commit!"),
				oid_to_hex(&oid));
		}
		if (repo_parse_commit(r, 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 repository *r,
			 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 = NULL;
	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 *committer = NULL;
	const char *hook_commit = NULL;
	enum commit_msg_cleanup_mode cleanup;
	int res = 0;

	if ((flags & CLEANUP_MSG) && (flags & VERBATIM_MSG))
		BUG("CLEANUP_MSG and VERBATIM_MSG are mutually exclusive");

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

	if (flags & AMEND_MSG) {
		const char *exclude_gpgsig[] = { "gpgsig", "gpgsig-sha256", NULL };
		const char *out_enc = get_commit_output_encoding();
		const char *message = repo_logmsg_reencode(r, 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);
		repo_unuse_commit_buffer(r, 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 &&
		   (!(flags & CREATE_ROOT_COMMIT) || (flags & AMEND_MSG))) {
		commit_list_insert(current_head, &parents);
	}

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

	if (!(flags & ALLOW_EMPTY)) {
		struct commit *first_parent = current_head;

		if (flags & AMEND_MSG) {
			if (current_head->parents) {
				first_parent = current_head->parents->item;
				if (repo_parse_commit(r, first_parent)) {
					res = error(_("could not parse HEAD commit"));
					goto out;
				}
			} else {
				first_parent = NULL;
			}
		}
		if (oideq(first_parent
			  ? get_commit_tree_oid(first_parent)
			  : the_hash_algo->empty_tree,
			  &tree)) {
			res = 1; /* run 'git commit' to display error message */
			goto out;
		}
	}

	if (hook_exists("prepare-commit-msg")) {
		res = run_prepare_commit_msg_hook(r, 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;
	}

	if (flags & CLEANUP_MSG)
		cleanup = COMMIT_MSG_CLEANUP_ALL;
	else if (flags & VERBATIM_MSG)
		cleanup = COMMIT_MSG_CLEANUP_NONE;
	else if ((opts->signoff || opts->record_origin) &&
		 !opts->explicit_cleanup)
		cleanup = COMMIT_MSG_CLEANUP_SPACE;
	else
		cleanup = opts->default_msg_cleanup;

	if (cleanup != COMMIT_MSG_CLEANUP_NONE)
		strbuf_stripspace(msg,
		  cleanup == COMMIT_MSG_CLEANUP_ALL ? comment_line_str : NULL);
	if ((flags & EDIT_MSG) && message_is_empty(msg, cleanup)) {
		res = 1; /* run 'git commit' to display error message */
		goto out;
	}

	if (opts->committer_date_is_author_date) {
		struct ident_split id;
		struct strbuf date = STRBUF_INIT;

		if (!opts->ignore_date) {
			if (split_ident_line(&id, author, (int)strlen(author)) < 0) {
				res = error(_("invalid author identity '%s'"),
					    author);
				goto out;
			}
			if (!id.date_begin) {
				res = error(_(
					"corrupt author: missing date information"));
				goto out;
			}
			strbuf_addf(&date, "@%.*s %.*s",
				    (int)(id.date_end - id.date_begin),
				    id.date_begin,
				    (int)(id.tz_end - id.tz_begin),
				    id.tz_begin);
		} else {
			reset_ident_date();
		}
		committer = fmt_ident(getenv("GIT_COMMITTER_NAME"),
				      getenv("GIT_COMMITTER_EMAIL"),
				      WANT_COMMITTER_IDENT,
				      opts->ignore_date ? NULL : date.buf,
				      IDENT_STRICT);
		strbuf_release(&date);
	} else {
		reset_ident_date();
	}

	if (opts->ignore_date) {
		struct ident_split id;
		char *name, *email;

		if (split_ident_line(&id, author, strlen(author)) < 0) {
			error(_("invalid author identity '%s'"), author);
			goto out;
		}
		name = xmemdupz(id.name_begin, id.name_end - id.name_begin);
		email = xmemdupz(id.mail_begin, id.mail_end - id.mail_begin);
		author = fmt_ident(name, email, WANT_AUTHOR_IDENT, NULL,
				   IDENT_STRICT);
		free(name);
		free(email);
	}

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

	if (update_head_with_reflog(current_head, oid, opts->reflog_message,
				    msg, &err)) {
		res = error("%s", err.buf);
		goto out;
	}

	run_commit_hook(0, r->index_file, NULL, "post-commit", NULL);
	if (flags & AMEND_MSG)
		commit_post_rewrite(r, current_head, oid);

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

	return res;
}

static int write_rebase_head(struct object_id *oid)
{
	if (update_ref("rebase", "REBASE_HEAD", oid,
		       NULL, REF_NO_DEREF, UPDATE_REFS_MSG_ON_ERR))
		return error(_("could not update %s"), "REBASE_HEAD");

	return 0;
}

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

	if (!(flags & EDIT_MSG) && !(flags & VERIFY_MSG)) {
		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(r, msg_file ? &sb : NULL,
				    author, opts, flags, &oid);
		strbuf_release(&sb);
		if (!res) {
			refs_delete_ref(get_main_ref_store(r), "",
					"CHERRY_PICK_HEAD", NULL, REF_NO_DEREF);
			unlink(git_path_merge_msg(r));
			if (!is_rebase_i(opts))
				print_commit_summary(r, NULL, &oid,
						SUMMARY_SHOW_AUTHOR_DATE);
			return res;
		}
	}
	if (res == 1) {
		if (is_rebase_i(opts) && oid)
			if (write_rebase_head(oid))
			    return -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 (repo_parse_commit(the_repository, commit))
		return error(_("could not parse commit %s"),
			     oid_to_hex(&commit->object.oid));
	if (commit->parents) {
		struct commit *parent = commit->parents->item;
		if (repo_parse_commit(the_repository, 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 oideq(ptree_oid, get_commit_tree_oid(commit));
}

/*
 * Should empty commits be allowed?  Return status:
 *    <0: Error in is_index_unchanged(r) or is_original_commit_empty(commit)
 *     0: Halt on empty commit
 *     1: Allow empty commit
 *     2: Drop empty commit
 */
static int allow_empty(struct repository *r,
		       struct replay_opts *opts,
		       struct commit *commit)
{
	int index_unchanged, originally_empty;

	/*
	 * For a commit that is initially empty, allow_empty determines if it
	 * should be kept or not
	 *
	 * For a commit that becomes empty, keep_redundant_commits and
	 * drop_redundant_commits determine whether the commit should be kept or
	 * dropped. If neither is specified, halt.
	 */
	index_unchanged = is_index_unchanged(r);
	if (index_unchanged < 0)
		return index_unchanged;
	if (!index_unchanged)
		return 0; /* we do not have to say --allow-empty */

	originally_empty = is_original_commit_empty(commit);
	if (originally_empty < 0)
		return originally_empty;
	if (originally_empty)
		return opts->allow_empty;
	else if (opts->keep_redundant_commits)
		return 1;
	else if (opts->drop_redundant_commits)
		return 2;
	else
		return 0;
}

static struct {
	char c;
	const char *str;
} todo_command_info[] = {
	[TODO_PICK] = { 'p', "pick" },
	[TODO_REVERT] = { 0,   "revert" },
	[TODO_EDIT] = { 'e', "edit" },
	[TODO_REWORD] = { 'r', "reword" },
	[TODO_FIXUP] = { 'f', "fixup" },
	[TODO_SQUASH] = { 's', "squash" },
	[TODO_EXEC] = { 'x', "exec" },
	[TODO_BREAK] = { 'b', "break" },
	[TODO_LABEL] = { 'l', "label" },
	[TODO_RESET] = { 't', "reset" },
	[TODO_MERGE] = { 'm', "merge" },
	[TODO_UPDATE_REF] = { 'u', "update-ref" },
	[TODO_NOOP] = { 0,   "noop" },
	[TODO_DROP] = { 'd', "drop" },
	[TODO_COMMENT] = { 0,   NULL },
};

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

static char command_to_char(const enum todo_command command)
{
	if (command < TODO_COMMENT)
		return todo_command_info[command].c;
	return 0;
}

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;
	}
}

enum todo_item_flags {
	TODO_EDIT_MERGE_MSG    = (1 << 0),
	TODO_REPLACE_FIXUP_MSG = (1 << 1),
	TODO_EDIT_FIXUP_MSG    = (1 << 2),
};

static const char first_commit_msg_str[] = N_("This is the 1st commit message:");
static const char nth_commit_msg_fmt[] = N_("This is the commit message #%d:");
static const char skip_first_commit_msg_str[] = N_("The 1st commit message will be skipped:");
static const char skip_nth_commit_msg_fmt[] = N_("The commit message #%d will be skipped:");
static const char combined_commit_msg_fmt[] = N_("This is a combination of %d commits.");

static int is_fixup_flag(enum todo_command command, unsigned flag)
{
	return command == TODO_FIXUP && ((flag & TODO_REPLACE_FIXUP_MSG) ||
					 (flag & TODO_EDIT_FIXUP_MSG));
}

/*
 * Wrapper around strbuf_add_commented_lines() which avoids double
 * commenting commit subjects.
 */
static void add_commented_lines(struct strbuf *buf, const void *str, size_t len)
{
	const char *s = str;
	while (starts_with_mem(s, len, comment_line_str)) {
		size_t count;
		const char *n = memchr(s, '\n', len);
		if (!n)
			count = len;
		else
			count = n - s + 1;
		strbuf_add(buf, s, count);
		s += count;
		len -= count;
	}
	strbuf_add_commented_lines(buf, s, len, comment_line_str);
}

/* Does the current fixup chain contain a squash command? */
static int seen_squash(struct replay_opts *opts)
{
	return starts_with(opts->current_fixups.buf, "squash") ||
		strstr(opts->current_fixups.buf, "\nsquash");
}

static void update_comment_bufs(struct strbuf *buf1, struct strbuf *buf2, int n)
{
	strbuf_setlen(buf1, 2);
	strbuf_addf(buf1, _(nth_commit_msg_fmt), n);
	strbuf_addch(buf1, '\n');
	strbuf_setlen(buf2, 2);
	strbuf_addf(buf2, _(skip_nth_commit_msg_fmt), n);
	strbuf_addch(buf2, '\n');
}

/*
 * Comment out any un-commented commit messages, updating the message comments
 * to say they will be skipped but do not comment out the empty lines that
 * surround commit messages and their comments.
 */
static void update_squash_message_for_fixup(struct strbuf *msg)
{
	void (*copy_lines)(struct strbuf *, const void *, size_t) = strbuf_add;
	struct strbuf buf1 = STRBUF_INIT, buf2 = STRBUF_INIT;
	const char *s, *start;
	char *orig_msg;
	size_t orig_msg_len;
	int i = 1;

	strbuf_addf(&buf1, "# %s\n", _(first_commit_msg_str));
	strbuf_addf(&buf2, "# %s\n", _(skip_first_commit_msg_str));
	s = start = orig_msg = strbuf_detach(msg, &orig_msg_len);
	while (s) {
		const char *next;
		size_t off;
		if (skip_prefix(s, buf1.buf, &next)) {
			/*
			 * Copy the last message, preserving the blank line
			 * preceding the current line
			 */
			off = (s > start + 1 && s[-2] == '\n') ? 1 : 0;
			copy_lines(msg, start, s - start - off);
			if (off)
				strbuf_addch(msg, '\n');
			/*
			 * The next message needs to be commented out but the
			 * message header is already commented out so just copy
			 * it and the blank line that follows it.
			 */
			strbuf_addbuf(msg, &buf2);
			if (*next == '\n')
				strbuf_addch(msg, *next++);
			start = s = next;
			copy_lines = add_commented_lines;
			update_comment_bufs(&buf1, &buf2, ++i);
		} else if (skip_prefix(s, buf2.buf, &next)) {
			off = (s > start + 1 && s[-2] == '\n') ? 1 : 0;
			copy_lines(msg, start, s - start - off);
			start = s - off;
			s = next;
			copy_lines = strbuf_add;
			update_comment_bufs(&buf1, &buf2, ++i);
		} else {
			s = strchr(s, '\n');
			if (s)
				s++;
		}
	}
	copy_lines(msg, start, orig_msg_len - (start - orig_msg));
	free(orig_msg);
	strbuf_release(&buf1);
	strbuf_release(&buf2);
}

static int append_squash_message(struct strbuf *buf, const char *body,
			 enum todo_command command, struct replay_opts *opts,
			 unsigned flag)
{
	const char *fixup_msg;
	size_t commented_len = 0, fixup_off;
	/*
	 * amend is non-interactive and not normally used with fixup!
	 * or squash! commits, so only comment out those subjects when
	 * squashing commit messages.
	 */
	if (starts_with(body, "amend!") ||
	    ((command == TODO_SQUASH || seen_squash(opts)) &&
	     (starts_with(body, "squash!") || starts_with(body, "fixup!"))))
		commented_len = commit_subject_length(body);

	strbuf_addf(buf, "\n%s ", comment_line_str);
	strbuf_addf(buf, _(nth_commit_msg_fmt),
		    ++opts->current_fixup_count + 1);
	strbuf_addstr(buf, "\n\n");
	strbuf_add_commented_lines(buf, body, commented_len, comment_line_str);
	/* buf->buf may be reallocated so store an offset into the buffer */
	fixup_off = buf->len;
	strbuf_addstr(buf, body + commented_len);

	/* fixup -C after squash behaves like squash */
	if (is_fixup_flag(command, flag) && !seen_squash(opts)) {
		/*
		 * We're replacing the commit message so we need to
		 * append the Signed-off-by: trailer if the user
		 * requested '--signoff'.
		 */
		if (opts->signoff)
			append_signoff(buf, 0, 0);

		if ((command == TODO_FIXUP) &&
		    (flag & TODO_REPLACE_FIXUP_MSG) &&
		    (file_exists(rebase_path_fixup_msg()) ||
		     !file_exists(rebase_path_squash_msg()))) {
			fixup_msg = skip_blank_lines(buf->buf + fixup_off);
			if (write_message(fixup_msg, strlen(fixup_msg),
					rebase_path_fixup_msg(), 0) < 0)
				return error(_("cannot write '%s'"),
					rebase_path_fixup_msg());
		} else {
			unlink(rebase_path_fixup_msg());
		}
	} else  {
		unlink(rebase_path_fixup_msg());
	}

	return 0;
}

static int update_squash_messages(struct repository *r,
				  enum todo_command command,
				  struct commit *commit,
				  struct replay_opts *opts,
				  unsigned flag)
{
	struct strbuf buf = STRBUF_INIT;
	int res = 0;
	const char *message, *body;
	const char *encoding = get_commit_output_encoding();

	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 = !starts_with(buf.buf, comment_line_str) ?
			buf.buf : strchrnul(buf.buf, '\n');

		strbuf_addf(&header, "%s ", comment_line_str);
		strbuf_addf(&header, _(combined_commit_msg_fmt),
			    opts->current_fixup_count + 2);
		strbuf_splice(&buf, 0, eol - buf.buf, header.buf, header.len);
		strbuf_release(&header);
		if (is_fixup_flag(command, flag) && !seen_squash(opts))
			update_squash_message_for_fixup(&buf);
	} else {
		struct object_id head;
		struct commit *head_commit;
		const char *head_message, *body;

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

		find_commit_subject(head_message, &body);
		if (command == TODO_FIXUP && !flag && write_message(body, strlen(body),
							rebase_path_fixup_msg(), 0) < 0) {
			repo_unuse_commit_buffer(r, head_commit, head_message);
			return error(_("cannot write '%s'"), rebase_path_fixup_msg());
		}
		strbuf_addf(&buf, "%s ", comment_line_str);
		strbuf_addf(&buf, _(combined_commit_msg_fmt), 2);
		strbuf_addf(&buf, "\n%s ", comment_line_str);
		strbuf_addstr(&buf, is_fixup_flag(command, flag) ?
			      _(skip_first_commit_msg_str) :
			      _(first_commit_msg_str));
		strbuf_addstr(&buf, "\n\n");
		if (is_fixup_flag(command, flag))
			strbuf_add_commented_lines(&buf, body, strlen(body),
						   comment_line_str);
		else
			strbuf_addstr(&buf, body);

		repo_unuse_commit_buffer(r, head_commit, head_message);
	}

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

	if (command == TODO_SQUASH || is_fixup_flag(command, flag)) {
		res = append_squash_message(&buf, body, command, opts, flag);
	} else if (command == TODO_FIXUP) {
		strbuf_addf(&buf, "\n%s ", comment_line_str);
		strbuf_addf(&buf, _(skip_nth_commit_msg_fmt),
			    ++opts->current_fixup_count + 1);
		strbuf_addstr(&buf, "\n\n");
		strbuf_add_commented_lines(&buf, body, strlen(body),
					   comment_line_str);
	} else
		return error(_("unknown command: %d"), command);
	repo_unuse_commit_buffer(r, commit, message);

	if (!res)
		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 &&
	    !repo_get_oid(the_repository, "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 should_edit(struct replay_opts *opts) {
	if (opts->edit < 0)
		/*
		 * Note that we only handle the case of non-conflicted
		 * commits; continue_single_pick() handles the conflicted
		 * commits itself instead of calling this function.
		 */
		return (opts->action == REPLAY_REVERT && isatty(0)) ? 1 : 0;
	return opts->edit;
}

static void refer_to_commit(struct replay_opts *opts,
			    struct strbuf *msgbuf, struct commit *commit)
{
	if (opts->commit_use_reference) {
		struct pretty_print_context ctx = {
			.abbrev = DEFAULT_ABBREV,
			.date_mode.type = DATE_SHORT,
		};
		repo_format_commit_message(the_repository, commit,
					   "%h (%s, %ad)", msgbuf, &ctx);
	} else {
		strbuf_addstr(msgbuf, oid_to_hex(&commit->object.oid));
	}
}

static int do_pick_commit(struct repository *r,
			  struct todo_item *item,
			  struct replay_opts *opts,
			  int final_fixup, int *check_todo)
{
	unsigned int flags = should_edit(opts) ? EDIT_MSG : 0;
	const char *msg_file = should_edit(opts) ? NULL : git_path_merge_msg(r);
	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, reword = 0, allow, drop_commit;
	enum todo_command command = item->command;
	struct commit *commit = item->commit;

	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 the merge machinery
		 * to work on.
		 */
		if (write_index_as_tree(&head, r->index, r->index_file, 0, NULL))
			return error(_("your index file is unmerged."));
	} else {
		unborn = repo_get_oid(r, "HEAD", &head);
		/* Do we want to generate a root commit? */
		if (is_pick_or_similar(command) && opts->have_squash_onto &&
		    oideq(&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(r, unborn ? empty_tree_oid_hex() : "HEAD",
				       NULL, 0))
			return error_dirty_index(r, opts);
	}
	discard_index(r->index);

	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 (1 < opts->mainline)
		/*
		 *  Non-first parent explicitly specified as mainline for
		 *  non-merge commit
		 */
		return error(_("commit %s does not have parent %d"),
			     oid_to_hex(&commit->object.oid), opts->mainline);
	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 && oideq(&parent->object.oid, &head)) ||
	     (!parent && unborn))) {
		if (is_rebase_i(opts))
			write_author_script(msg.message);
		res = fast_forward_to(r, &commit->object.oid, &head, unborn,
			opts);
		if (res || command != TODO_REWORD)
			goto leave;
		reword = 1;
		msg_file = NULL;
		goto fast_forward_edit;
	}
	if (parent && repo_parse_commit(r, 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) {
		const char *orig_subject;

		base = commit;
		base_label = msg.label;
		next = parent;
		next_label = msg.parent_label;
		if (opts->commit_use_reference) {
			strbuf_addstr(&msgbuf,
				"# *** SAY WHY WE ARE REVERTING ON THE TITLE LINE ***");
		} else if (skip_prefix(msg.subject, "Revert \"", &orig_subject) &&
			   /*
			    * We don't touch pre-existing repeated reverts, because
			    * theoretically these can be nested arbitrarily deeply,
			    * thus requiring excessive complexity to deal with.
			    */
			   !starts_with(orig_subject, "Revert \"")) {
			strbuf_addstr(&msgbuf, "Reapply \"");
			strbuf_addstr(&msgbuf, orig_subject);
		} else {
			strbuf_addstr(&msgbuf, "Revert \"");
			strbuf_addstr(&msgbuf, msg.subject);
			strbuf_addstr(&msgbuf, "\"");
		}
		strbuf_addstr(&msgbuf, "\n\nThis reverts commit ");
		refer_to_commit(opts, &msgbuf, commit);

		if (commit->parents && commit->parents->next) {
			strbuf_addstr(&msgbuf, ", reversing\nchanges made to ");
			refer_to_commit(opts, &msgbuf, parent);
		}
		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)
		reword = 1;
	else if (is_fixup(command)) {
		if (update_squash_messages(r, command, commit,
					   opts, item->flags)) {
			res = -1;
			goto leave;
		}
		flags |= AMEND_MSG;
		if (!final_fixup)
			msg_file = rebase_path_squash_msg();
		else if (file_exists(rebase_path_fixup_msg())) {
			flags |= VERBATIM_MSG;
			msg_file = rebase_path_fixup_msg();
		} else {
			const char *dest = git_path_squash_msg(r);
			unlink(dest);
			if (copy_file(dest, rebase_path_squash_msg(), 0666)) {
				res = error(_("could not copy '%s' to '%s'"),
					    rebase_path_squash_msg(), dest);
				goto leave;
			}
			unlink(git_path_merge_msg(r));
			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") ||
		 !strcmp(opts->strategy, "ort") ||
		 command == TODO_REVERT) {
		res = do_recursive_merge(r, 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(r), 0);
	} else {
		struct commit_list *common = NULL;
		struct commit_list *remotes = NULL;

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

		commit_list_insert(base, &common);
		commit_list_insert(next, &remotes);
		res |= try_merge_command(r, opts->strategy,
					 opts->xopts.nr, opts->xopts.v,
					common, oid_to_hex(&head), remotes);
		free_commit_list(common);
		free_commit_list(remotes);
	}

	/*
	 * 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 || command == TODO_REWORD ||
	     command == TODO_EDIT) && !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(r, commit), msg.subject);
		print_advice(r, res == 1, opts);
		repo_rerere(r, opts->allow_rerere_auto);
		goto leave;
	}

	drop_commit = 0;
	allow = allow_empty(r, opts, commit);
	if (allow < 0) {
		res = allow;
		goto leave;
	} else if (allow == 1) {
		flags |= ALLOW_EMPTY;
	} else if (allow == 2) {
		drop_commit = 1;
		refs_delete_ref(get_main_ref_store(r), "", "CHERRY_PICK_HEAD",
				NULL, REF_NO_DEREF);
		unlink(git_path_merge_msg(r));
		refs_delete_ref(get_main_ref_store(r), "", "AUTO_MERGE",
				NULL, REF_NO_DEREF);
		fprintf(stderr,
			_("dropping %s %s -- patch contents already upstream\n"),
			oid_to_hex(&commit->object.oid), msg.subject);
	} /* else allow == 0 and there's nothing special to do */
	if (!opts->no_commit && !drop_commit) {
		if (author || command == TODO_REVERT || (flags & AMEND_MSG))
			res = do_commit(r, msg_file, author, opts, flags,
					commit? &commit->object.oid : NULL);
		else
			res = error(_("unable to parse commit author"));
		*check_todo = !!(flags & EDIT_MSG);
		if (!res && reword) {
fast_forward_edit:
			res = run_git_commit(NULL, opts, EDIT_MSG |
					     VERIFY_MSG | AMEND_MSG |
					     (flags & ALLOW_EMPTY));
			*check_todo = 1;
		}
	}


	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);
	strbuf_release(&msgbuf);
	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"));

	return 0;
}

static int read_and_refresh_cache(struct repository *r,
				  struct replay_opts *opts)
{
	struct lock_file index_lock = LOCK_INIT;
	int index_fd = repo_hold_locked_index(r, &index_lock, 0);
	if (repo_read_index(r) < 0) {
		rollback_lock_file(&index_lock);
		return error(_("git %s: failed to read the index"),
			action_name(opts));
	}
	refresh_index(r->index, REFRESH_QUIET|REFRESH_UNMERGED, NULL, NULL, NULL);

	if (index_fd >= 0) {
		if (write_locked_index(r->index, &index_lock,
				       COMMIT_LOCK | SKIP_IF_UNCHANGED)) {
			return error(_("git %s: failed to refresh the index"),
				action_name(opts));
		}
	}

	/*
	 * If we are resolving merges in any way other than "ort", then
	 * expand the sparse index.
	 */
	if (opts->strategy && strcmp(opts->strategy, "ort"))
		ensure_full_index(r->index);
	return 0;
}

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++;
}

const char *todo_item_get_arg(struct todo_list *todo_list,
			      struct todo_item *item)
{
	return todo_list->buf.buf + item->arg_offset;
}

static int is_command(enum todo_command command, const char **bol)
{
	const char *str = todo_command_info[command].str;
	const char nick = todo_command_info[command].c;
	const char *p = *bol;

	return (skip_prefix(p, str, &p) || (nick && *p++ == nick)) &&
		(*p == ' ' || *p == '\t' || *p == '\n' || *p == '\r' || !*p) &&
		(*bol = p);
}

static int check_label_or_ref_arg(enum todo_command command, const char *arg)
{
	switch (command) {
	case TODO_LABEL:
		/*
		 * '#' is not a valid label as the merge command uses it to
		 * separate merge parents from the commit subject.
		 */
		if (!strcmp(arg, "#") ||
		    check_refname_format(arg, REFNAME_ALLOW_ONELEVEL))
			return error(_("'%s' is not a valid label"), arg);
		break;

	case TODO_UPDATE_REF:
		if (check_refname_format(arg, REFNAME_ALLOW_ONELEVEL))
			return error(_("'%s' is not a valid refname"), arg);
		if (check_refname_format(arg, 0))
			return error(_("update-ref requires a fully qualified "
				       "refname e.g. refs/heads/%s"), arg);
		break;

	default:
		BUG("unexpected todo_command");
	}

	return 0;
}

static int parse_insn_line(struct repository *r, struct todo_item *item,
			   const char *buf, 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' || starts_with_mem(bol, eol - bol, comment_line_str)) {
		item->command = TODO_COMMENT;
		item->commit = NULL;
		item->arg_offset = bol - buf;
		item->arg_len = eol - bol;
		return 0;
	}

	for (i = 0; i < TODO_COMMENT; i++)
		if (is_command(i, &bol)) {
			item->command = i;
			break;
		}
	if (i >= TODO_COMMENT)
		return error(_("invalid command '%.*s'"),
			     (int)strcspn(bol, " \t\r\n"), bol);

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

	if (item->command == TODO_NOOP || item->command == TODO_BREAK) {
		if (bol != eol)
			return error(_("%s does not accept arguments: '%s'"),
				     command_to_string(item->command), bol);
		item->commit = NULL;
		item->arg_offset = bol - buf;
		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->command == TODO_UPDATE_REF) {
		int ret = 0;

		item->commit = NULL;
		item->arg_offset = bol - buf;
		item->arg_len = (int)(eol - bol);
		if (item->command == TODO_LABEL ||
		    item->command == TODO_UPDATE_REF) {
			saved = *eol;
			*eol = '\0';
			ret = check_label_or_ref_arg(item->command, bol);
			*eol = saved;
		}
		return ret;
	}

	if (item->command == TODO_FIXUP) {
		if (skip_prefix(bol, "-C", &bol)) {
			bol += strspn(bol, " \t");
			item->flags |= TODO_REPLACE_FIXUP_MSG;
		} else if (skip_prefix(bol, "-c", &bol)) {
			bol += strspn(bol, " \t");
			item->flags |= TODO_EDIT_FIXUP_MSG;
		}
	}

	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_offset = bol - buf;
			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 = repo_get_oid(r, bol, &commit_oid);
	if (status < 0)
		error(_("could not parse '%s'"), bol); /* return later */
	*end_of_object_name = saved;

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

	if (status < 0)
		return status;

	item->commit = lookup_commit_reference(r, &commit_oid);
	return item->commit ? 0 : -1;
}

int sequencer_get_last_command(struct repository *r UNUSED, enum replay_action *action)
{
	const char *todo_file, *bol;
	struct strbuf buf = STRBUF_INIT;
	int ret = 0;

	todo_file = git_path_todo_file();
	if (strbuf_read_file(&buf, todo_file, 0) < 0) {
		if (errno == ENOENT || errno == ENOTDIR)
			return -1;
		else
			return error_errno("unable to open '%s'", todo_file);
	}
	bol = buf.buf + strspn(buf.buf, " \t\r\n");
	if (is_command(TODO_PICK, &bol) && (*bol == ' ' || *bol == '\t'))
		*action = REPLAY_PICK;
	else if (is_command(TODO_REVERT, &bol) &&
		 (*bol == ' ' || *bol == '\t'))
		*action = REPLAY_REVERT;
	else
		ret = -1;

	strbuf_release(&buf);

	return ret;
}

int todo_list_parse_insn_buffer(struct repository *r, 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());

	todo_list->current = todo_list->nr = todo_list->total_nr = 0;

	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(r, item, buf, p, eol)) {
			res = error(_("invalid line %d: %.*s"),
				i, (int)(eol - p), p);
			item->command = TODO_COMMENT + 1;
			item->arg_offset = p - buf;
			item->arg_len = (int)(eol - p);
			item->commit = NULL;
		}

		if (item->command != TODO_COMMENT)
			todo_list->total_nr++;

		if (fixup_okay)
			; /* do nothing */
		else if (is_fixup(item->command))
			res = 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 have_finished_the_last_pick(void)
{
	struct strbuf buf = STRBUF_INIT;
	const char *eol;
	const char *todo_path = git_path_todo_file();
	int ret = 0;

	if (strbuf_read_file(&buf, todo_path, 0) < 0) {
		if (errno == ENOENT) {
			return 0;
		} else {
			error_errno("unable to open '%s'", todo_path);
			return 0;
		}
	}
	/* If there is only one line then we are done */
	eol = strchr(buf.buf, '\n');
	if (!eol || !eol[1])
		ret = 1;

	strbuf_release(&buf);

	return ret;
}

void sequencer_post_commit_cleanup(struct repository *r, int verbose)
{
	struct replay_opts opts = REPLAY_OPTS_INIT;
	int need_cleanup = 0;

	if (refs_ref_exists(get_main_ref_store(r), "CHERRY_PICK_HEAD")) {
		if (!refs_delete_ref(get_main_ref_store(r), "",
				     "CHERRY_PICK_HEAD", NULL, REF_NO_DEREF) &&
		    verbose)
			warning(_("cancelling a cherry picking in progress"));
		opts.action = REPLAY_PICK;
		need_cleanup = 1;
	}

	if (refs_ref_exists(get_main_ref_store(r), "REVERT_HEAD")) {
		if (!refs_delete_ref(get_main_ref_store(r), "", "REVERT_HEAD",
				     NULL, REF_NO_DEREF) &&
		    verbose)
			warning(_("cancelling a revert in progress"));
		opts.action = REPLAY_REVERT;
		need_cleanup = 1;
	}

	refs_delete_ref(get_main_ref_store(r), "", "AUTO_MERGE",
			NULL, REF_NO_DEREF);

	if (!need_cleanup)
		return;

	if (!have_finished_the_last_pick())
		return;

	sequencer_remove_state(&opts);
}

static void todo_list_write_total_nr(struct todo_list *todo_list)
{
	FILE *f = fopen_or_warn(rebase_path_msgtotal(), "w");

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

static int read_populate_todo(struct repository *r,
			      struct todo_list *todo_list,
			      struct replay_opts *opts)
{
	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 = todo_list_parse_insn_buffer(r, todo_list