1 files changed, 479 insertions, 462 deletions

diff --git a/sequencer.c b/sequencer.c
index 95dda23eee..ab74b6baf1 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -55,8 +55,7 @@ static GIT_PATH_FUNC(rebase_path, "rebase-merge")
  * file and written to the tail of 'done'.
  */
 GIT_PATH_FUNC(rebase_path_todo, "rebase-merge/git-rebase-todo")
-static GIT_PATH_FUNC(rebase_path_todo_backup,
-		     "rebase-merge/git-rebase-todo.backup")
+GIT_PATH_FUNC(rebase_path_todo_backup, "rebase-merge/git-rebase-todo.backup")
 
 /*
  * The rebase command lines that have already been processed. A line
@@ -172,17 +171,22 @@ static int git_sequencer_config(const char *k, const char *v, void *cb)
 		if (status)
 			return status;
 
-		if (!strcmp(s, "verbatim"))
+		if (!strcmp(s, "verbatim")) {
 			opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_NONE;
-		else if (!strcmp(s, "whitespace"))
+			opts->explicit_cleanup = 1;
+		} else if (!strcmp(s, "whitespace")) {
 			opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_SPACE;
-		else if (!strcmp(s, "strip"))
+			opts->explicit_cleanup = 1;
+		} 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
+			opts->explicit_cleanup = 1;
+		} else if (!strcmp(s, "scissors")) {
+			opts->default_msg_cleanup = COMMIT_MSG_CLEANUP_SCISSORS;
+			opts->explicit_cleanup = 1;
+		} else {
 			warning(_("invalid commit message cleanup mode '%s'"),
 				  s);
+		}
 
 		free((char *)s);
 		return status;
@@ -384,8 +388,8 @@ static void print_advice(struct repository *r, int show_hint,
 	}
 }
 
-int write_message(const void *buf, size_t len, const char *filename,
-		  int append_eol)
+static int write_message(const void *buf, size_t len, const char *filename,
+			 int append_eol)
 {
 	struct lock_file msg_file = LOCK_INIT;
 
@@ -511,11 +515,54 @@ static int fast_forward_to(struct repository *r,
 	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)
+	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_addch(msgbuf, comment_line_char);
+	}
+
 	strbuf_addch(msgbuf, '\n');
 	strbuf_commented_addf(msgbuf, "Conflicts:\n");
 	for (i = 0; i < istate->cache_nr;) {
@@ -583,7 +630,8 @@ static int do_recursive_merge(struct repository *r,
 			_(action_name(opts)));
 
 	if (!clean)
-		append_conflicts_hint(r->index, msgbuf);
+		append_conflicts_hint(r->index, msgbuf,
+				      opts->default_msg_cleanup);
 
 	return !clean;
 }
@@ -719,7 +767,7 @@ static int parse_key_value_squoted(char *buf, struct string_list *list)
  *	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 old
+ * 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.
@@ -902,7 +950,6 @@ static int run_git_commit(struct repository *r,
 			  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;
@@ -972,7 +1019,7 @@ static int run_git_commit(struct repository *r,
 		argv_array_push(&cmd.args, "-e");
 	else if (!(flags & CLEANUP_MSG) &&
 		 !opts->signoff && !opts->record_origin &&
-		 git_config_get_value("commit.cleanup", &value))
+		 !opts->explicit_cleanup)
 		argv_array_push(&cmd.args, "--cleanup=verbatim");
 
 	if ((flags & ALLOW_EMPTY))
@@ -1013,6 +1060,16 @@ static int rest_is_empty(const struct strbuf *sb, int start)
 	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);
+}
+
 /*
  * Find out if the message in the strbuf contains only whitespace and
  * Signed-off-by lines.
@@ -1383,8 +1440,13 @@ static int try_to_commit(struct repository *r,
 		msg = &commit_msg;
 	}
 
-	cleanup = (flags & CLEANUP_MSG) ? COMMIT_MSG_CLEANUP_ALL :
-					  opts->default_msg_cleanup;
+	if (flags & CLEANUP_MSG)
+		cleanup = COMMIT_MSG_CLEANUP_ALL;
+	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);
@@ -1513,32 +1575,6 @@ static int allow_empty(struct repository *r,
 		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_BREAK,
-	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;
@@ -2021,26 +2057,7 @@ 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)
+void todo_list_release(struct todo_list *todo_list)
 {
 	strbuf_release(&todo_list->buf);
 	FREE_AND_NULL(todo_list->items);
@@ -2053,8 +2070,14 @@ static struct todo_item *append_new_todo(struct todo_list *todo_list)
 	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 parse_insn_line(struct repository *r, struct todo_item *item,
-			   const char *bol, char *eol)
+			   const char *buf, const char *bol, char *eol)
 {
 	struct object_id commit_oid;
 	char *end_of_object_name;
@@ -2068,7 +2091,7 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
 	if (bol == eol || *bol == '\r' || *bol == comment_line_char) {
 		item->command = TODO_COMMENT;
 		item->commit = NULL;
-		item->arg = bol;
+		item->arg_offset = bol - buf;
 		item->arg_len = eol - bol;
 		return 0;
 	}
@@ -2095,7 +2118,7 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
 			return error(_("%s does not accept arguments: '%s'"),
 				     command_to_string(item->command), bol);
 		item->commit = NULL;
-		item->arg = bol;
+		item->arg_offset = bol - buf;
 		item->arg_len = eol - bol;
 		return 0;
 	}
@@ -2107,7 +2130,7 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
 	if (item->command == TODO_EXEC || item->command == TODO_LABEL ||
 	    item->command == TODO_RESET) {
 		item->commit = NULL;
-		item->arg = bol;
+		item->arg_offset = bol - buf;
 		item->arg_len = (int)(eol - bol);
 		return 0;
 	}
@@ -2121,7 +2144,7 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
 		} else {
 			item->flags |= TODO_EDIT_MERGE_MSG;
 			item->commit = NULL;
-			item->arg = bol;
+			item->arg_offset = bol - buf;
 			item->arg_len = (int)(eol - bol);
 			return 0;
 		}
@@ -2133,23 +2156,62 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
 	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);
+	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 -1;
+		return error(_("could not parse '%.*s'"),
+			     (int)(end_of_object_name - bol), bol);
 
 	item->commit = lookup_commit_reference(r, &commit_oid);
 	return !item->commit;
 }
 
-static int parse_insn_buffer(struct repository *r, char *buf,
-			     struct todo_list *todo_list)
+int sequencer_get_last_command(struct repository *r, enum replay_action *action)
+{
+	struct todo_item item;
+	char *eol;
+	const char *todo_file;
+	struct strbuf buf = STRBUF_INIT;
+	int ret = -1;
+
+	todo_file = git_path_todo_file();
+	if (strbuf_read_file(&buf, todo_file, 0) < 0) {
+		if (errno == ENOENT)
+			return -1;
+		else
+			return error_errno("unable to open '%s'", todo_file);
+	}
+	eol = strchrnul(buf.buf, '\n');
+	if (buf.buf != eol && eol[-1] == '\r')
+		eol--; /* strip Carriage Return */
+	if (parse_insn_line(r, &item, buf.buf, buf.buf, eol))
+		goto fail;
+	if (item.command == TODO_PICK)
+		*action = REPLAY_PICK;
+	else if (item.command == TODO_REVERT)
+		*action = REPLAY_REVERT;
+	else
+		goto fail;
+
+	ret = 0;
+
+ fail:
+	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 = 0;
+
 	for (i = 1; *p; i++, p = next_p) {
 		char *eol = strchrnul(p, '\n');
 
@@ -2160,10 +2222,13 @@ static int parse_insn_buffer(struct repository *r, char *buf,
 
 		item = append_new_todo(todo_list);
 		item->offset_in_buf = p - todo_list->buf.buf;
-		if (parse_insn_line(r, item, p, eol)) {
+		if (parse_insn_line(r, item, buf, p, eol)) {
 			res = error(_("invalid line %d: %.*s"),
 				i, (int)(eol - p), p);
-			item->command = TODO_NOOP;
+			item->command = TODO_COMMENT + 1;
+			item->arg_offset = p - buf;
+			item->arg_len = (int)(eol - p);
+			item->commit = NULL;
 		}
 
 		if (fixup_okay)
@@ -2221,6 +2286,57 @@ static ssize_t strbuf_read_file_or_whine(struct strbuf *sb, const char *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)
+{
+	struct replay_opts opts = REPLAY_OPTS_INIT;
+	int need_cleanup = 0;
+
+	if (file_exists(git_path_cherry_pick_head(r))) {
+		unlink(git_path_cherry_pick_head(r));
+		opts.action = REPLAY_PICK;
+		need_cleanup = 1;
+	}
+
+	if (file_exists(git_path_revert_head(r))) {
+		unlink(git_path_revert_head(r));
+		opts.action = REPLAY_REVERT;
+		need_cleanup = 1;
+	}
+
+	if (!need_cleanup)
+		return;
+
+	if (!have_finished_the_last_pick())
+		return;
+
+	sequencer_remove_state(&opts);
+}
+
 static int read_populate_todo(struct repository *r,
 			      struct todo_list *todo_list,
 			      struct replay_opts *opts)
@@ -2238,7 +2354,7 @@ static int read_populate_todo(struct repository *r,
 		return error(_("could not stat '%s'"), todo_file);
 	fill_stat_data(&todo_list->stat, &st);
 
-	res = parse_insn_buffer(r, todo_list->buf.buf, todo_list);
+	res = todo_list_parse_insn_buffer(r, todo_list->buf.buf, todo_list);
 	if (res) {
 		if (is_rebase_i(opts))
 			return error(_("please fix this using "
@@ -2269,7 +2385,7 @@ static int read_populate_todo(struct repository *r,
 		FILE *f = fopen_or_warn(rebase_path_msgtotal(), "w");
 
 		if (strbuf_read_file(&done.buf, rebase_path_done(), 0) > 0 &&
-		    !parse_insn_buffer(r, done.buf.buf, &done))
+		    !todo_list_parse_insn_buffer(r, done.buf.buf, &done))
 			todo_list->done_nr = count_commands(&done);
 		else
 			todo_list->done_nr = 0;
@@ -2308,6 +2424,15 @@ static int populate_opts_cb(const char *key, const char *value, void *data)
 		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.allow-empty"))
+		opts->allow_empty =
+			git_config_bool_or_int(key, value, &error_flag);
+	else if (!strcmp(key, "options.allow-empty-message"))
+		opts->allow_empty_message =
+			git_config_bool_or_int(key, value, &error_flag);
+	else if (!strcmp(key, "options.keep-redundant-commits"))
+		opts->keep_redundant_commits =
+			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"))
@@ -2327,7 +2452,10 @@ static int populate_opts_cb(const char *key, const char *value, void *data)
 		opts->allow_rerere_auto =
 			git_config_bool_or_int(key, value, &error_flag) ?
 				RERERE_AUTOUPDATE : RERERE_NOAUTOUPDATE;
-	else
+	else if (!strcmp(key, "options.default-msg-cleanup")) {
+		opts->explicit_cleanup = 1;
+		opts->default_msg_cleanup = get_cleanup_mode(value, 1);
+	} else
 		return error(_("invalid key: %s"), key);
 
 	if (!error_flag)
@@ -2452,14 +2580,15 @@ static void write_strategy_opts(struct replay_opts *opts)
 }
 
 int write_basic_state(struct replay_opts *opts, const char *head_name,
-		      const char *onto, const char *orig_head)
+		      struct commit *onto, const char *orig_head)
 {
 	const char *quiet = getenv("GIT_QUIET");
 
 	if (head_name)
 		write_file(rebase_path_head_name(), "%s\n", head_name);
 	if (onto)
-		write_file(rebase_path_onto(), "%s\n", onto);
+		write_file(rebase_path_onto(), "%s\n",
+			   oid_to_hex(&onto->object.oid));
 	if (orig_head)
 		write_file(rebase_path_orig_head(), "%s\n", orig_head);
 
@@ -2506,7 +2635,7 @@ static int walk_revs_populate_todo(struct todo_list *todo_list,
 
 		item->command = command;
 		item->commit = commit;
-		item->arg = NULL;
+		item->arg_offset = 0;
 		item->arg_len = 0;
 		item->offset_in_buf = todo_list->buf.len;
 		subject_len = find_commit_subject(commit_buffer, &subject);
@@ -2701,36 +2830,59 @@ static int save_opts(struct replay_opts *opts)
 	int res = 0;
 
 	if (opts->no_commit)
-		res |= git_config_set_in_file_gently(opts_file, "options.no-commit", "true");
+		res |= git_config_set_in_file_gently(opts_file,
+					"options.no-commit", "true");
 	if (opts->edit)
-		res |= git_config_set_in_file_gently(opts_file, "options.edit", "true");
+		res |= git_config_set_in_file_gently(opts_file,
+					"options.edit", "true");
+	if (opts->allow_empty)
+		res |= git_config_set_in_file_gently(opts_file,
+					"options.allow-empty", "true");
+	if (opts->allow_empty_message)
+		res |= git_config_set_in_file_gently(opts_file,
+				"options.allow-empty-message", "true");
+	if (opts->keep_redundant_commits)
+		res |= git_config_set_in_file_gently(opts_file,
+				"options.keep-redundant-commits", "true");
 	if (opts->signoff)
-		res |= git_config_set_in_file_gently(opts_file, "options.signoff", "true");
+		res |= git_config_set_in_file_gently(opts_file,
+					"options.signoff", "true");
 	if (opts->record_origin)
-		res |= git_config_set_in_file_gently(opts_file, "options.record-origin", "true");
+		res |= git_config_set_in_file_gently(opts_file,
+					"options.record-origin", "true");
 	if (opts->allow_ff)
-		res |= git_config_set_in_file_gently(opts_file, "options.allow-ff", "true");
+		res |= git_config_set_in_file_gently(opts_file,
+					"options.allow-ff", "true");
 	if (opts->mainline) {
 		struct strbuf buf = STRBUF_INIT;
 		strbuf_addf(&buf, "%d", opts->mainline);
-		res |= git_config_set_in_file_gently(opts_file, "options.mainline", buf.buf);
+		res |= git_config_set_in_file_gently(opts_file,
+					"options.mainline", buf.buf);
 		strbuf_release(&buf);
 	}
 	if (opts->strategy)
-		res |= git_config_set_in_file_gently(opts_file, "options.strategy", opts->strategy);
+		res |= git_config_set_in_file_gently(opts_file,
+					"options.strategy", opts->strategy);
 	if (opts->gpg_sign)
-		res |= git_config_set_in_file_gently(opts_file, "options.gpg-sign", opts->gpg_sign);
+		res |= git_config_set_in_file_gently(opts_file,
+					"options.gpg-sign", opts->gpg_sign);
 	if (opts->xopts) {
 		int i;
 		for (i = 0; i < opts->xopts_nr; i++)
 			res |= git_config_set_multivar_in_file_gently(opts_file,
-							"options.strategy-option",
-							opts->xopts[i], "^$", 0);
+					"options.strategy-option",
+					opts->xopts[i], "^$", 0);
 	}
 	if (opts->allow_rerere_auto)
-		res |= git_config_set_in_file_gently(opts_file, "options.allow-rerere-auto",
-						     opts->allow_rerere_auto == RERERE_AUTOUPDATE ?
-						     "true" : "false");
+		res |= git_config_set_in_file_gently(opts_file,
+				"options.allow-rerere-auto",
+				opts->allow_rerere_auto == RERERE_AUTOUPDATE ?
+				"true" : "false");
+
+	if (opts->explicit_cleanup)
+		res |= git_config_set_in_file_gently(opts_file,
+				"options.default-msg-cleanup",
+				describe_cleanup_mode(opts->default_msg_cleanup));
 	return res;
 }
 
@@ -3249,6 +3401,10 @@ static int do_merge(struct repository *r,
 		rollback_lock_file(&lock);
 		ret = fast_forward_to(r, &commit->object.oid,
 				      &head_commit->object.oid, 0, opts);
+		if (flags & TODO_EDIT_MERGE_MSG) {
+			run_commit_flags |= AMEND_MSG;
+			goto fast_forward_edit;
+		}
 		goto leave_merge;
 	}
 
@@ -3352,6 +3508,7 @@ static int do_merge(struct repository *r,
 		 * value (a negative one would indicate that the `merge`
 		 * command needs to be rescheduled).
 		 */
+	fast_forward_edit:
 		ret = !!run_git_commit(r, git_path_merge_msg(r), opts,
 				       run_commit_flags);
 
@@ -3452,10 +3609,11 @@ static const char *reflog_message(struct replay_opts *opts,
 	return buf.buf;
 }
 
-static int run_git_checkout(struct replay_opts *opts, const char *commit,
-			    const char *action)
+static int run_git_checkout(struct repository *r, struct replay_opts *opts,
+			    const char *commit, const char *action)
 {
 	struct child_process cmd = CHILD_PROCESS_INIT;
+	int ret;
 
 	cmd.git_cmd = 1;
 
@@ -3464,26 +3622,32 @@ static int run_git_checkout(struct replay_opts *opts, const char *commit,
 	argv_array_pushf(&cmd.env_array, GIT_REFLOG_ACTION "=%s", action);
 
 	if (opts->verbose)
-		return run_command(&cmd);
+		ret = run_command(&cmd);
 	else
-		return run_command_silent_on_success(&cmd);
+		ret = run_command_silent_on_success(&cmd);
+
+	if (!ret)
+		discard_index(r->index);
+
+	return ret;
 }
 
-int prepare_branch_to_be_rebased(struct replay_opts *opts, const char *commit)
+int prepare_branch_to_be_rebased(struct repository *r, struct replay_opts *opts,
+				 const char *commit)
 {
 	const char *action;
 
 	if (commit && *commit) {
 		action = reflog_message(opts, "start", "checkout %s", commit);
-		if (run_git_checkout(opts, commit, action))
+		if (run_git_checkout(r, opts, commit, action))
 			return error(_("could not checkout %s"), commit);
 	}
 
 	return 0;
 }
 
-static int checkout_onto(struct replay_opts *opts,
-			 const char *onto_name, const char *onto,
+static int checkout_onto(struct repository *r, struct replay_opts *opts,
+			 const char *onto_name, const struct object_id *onto,
 			 const char *orig_head)
 {
 	struct object_id oid;
@@ -3492,7 +3656,7 @@ static int checkout_onto(struct replay_opts *opts,
 	if (get_oid(orig_head, &oid))
 		return error(_("%s: not a valid OID"), orig_head);
 
-	if (run_git_checkout(opts, onto, action)) {
+	if (run_git_checkout(r, opts, oid_to_hex(onto), action)) {
 		apply_autostash(opts);
 		sequencer_remove_state(opts);
 		return error(_("could not detach HEAD"));
@@ -3545,6 +3709,8 @@ static int pick_commits(struct repository *r,
 
 	while (todo_list->current < todo_list->nr) {
 		struct todo_item *item = todo_list->items + todo_list->current;
+		const char *arg = todo_item_get_arg(todo_list, item);
+
 		if (save_todo(todo_list, opts))
 			return -1;
 		if (is_rebase_i(opts)) {
@@ -3597,10 +3763,9 @@ static int pick_commits(struct repository *r,
 					fprintf(stderr,
 						_("Stopped at %s...  %.*s\n"),
 						short_commit_name(commit),
-						item->arg_len, item->arg);
+						item->arg_len, arg);
 				return error_with_patch(r, commit,
-					item->arg, item->arg_len, opts, res,
-					!res);
+					arg, item->arg_len, opts, res, !res);
 			}
 			if (is_rebase_i(opts) && !res)
 				record_in_rewritten(&item->commit->object.oid,
@@ -3609,7 +3774,7 @@ static int pick_commits(struct repository *r,
 				if (res == 1)
 					intend_to_amend();
 				return error_failed_squash(r, item->commit, opts,
-					item->arg_len, item->arg);
+					item->arg_len, arg);
 			} else if (res && is_rebase_i(opts) && item->commit) {
 				int to_amend = 0;
 				struct object_id oid;
@@ -3628,19 +3793,18 @@ static int pick_commits(struct repository *r,
 					to_amend = 1;
 
 				return res | error_with_patch(r, item->commit,
-						item->arg, item->arg_len, opts,
+						arg, item->arg_len, opts,
 						res, to_amend);
 			}
 		} else if (item->command == TODO_EXEC) {
-			char *end_of_arg = (char *)(item->arg + item->arg_len);
+			char *end_of_arg = (char *)(arg + item->arg_len);
 			int saved = *end_of_arg;
 			struct stat st;
 
 			*end_of_arg = '\0';
-			res = do_exec(r, item->arg);
+			res = do_exec(r, arg);
 			*end_of_arg = saved;
 
-			/* Reread the todo file if it has changed. */
 			if (res) {
 				if (opts->reschedule_failed_exec)
 					reschedule = 1;
@@ -3648,6 +3812,7 @@ static int pick_commits(struct repository *r,
 				res = error_errno(_("could not stat '%s'"),
 						  get_todo_path(opts));
 			else if (match_stat_data(&todo_list->stat, &st)) {
+				/* Reread the todo file if it has changed. */
 				todo_list_release(todo_list);
 				if (read_populate_todo(r, todo_list, opts))
 					res = -1; /* message was printed */
@@ -3655,14 +3820,14 @@ static int pick_commits(struct repository *r,
 				todo_list->current = -1;
 			}
 		} else if (item->command == TODO_LABEL) {
-			if ((res = do_label(r, item->arg, item->arg_len)))
+			if ((res = do_label(r, arg, item->arg_len)))
 				reschedule = 1;
 		} else if (item->command == TODO_RESET) {
-			if ((res = do_reset(r, item->arg, item->arg_len, opts)))
+			if ((res = do_reset(r, arg, item->arg_len, opts)))
 				reschedule = 1;
 		} else if (item->command == TODO_MERGE) {
 			if ((res = do_merge(r, item->commit,
-					    item->arg, item->arg_len,
+					    arg, item->arg_len,
 					    item->flags, opts)) < 0)
 				reschedule = 1;
 			else if (item->commit)
@@ -3671,9 +3836,8 @@ static int pick_commits(struct repository *r,
 			if (res > 0)
 				/* failed with merge conflicts */
 				return error_with_patch(r, item->commit,
-							item->arg,
-							item->arg_len, opts,
-							res, 0);
+							arg, item->arg_len,
+							opts, res, 0);
 		} else if (!is_noop(item->command))
 			return error(_("unknown command %d"), item->command);
 
@@ -3688,9 +3852,8 @@ static int pick_commits(struct repository *r,
 			if (item->commit)
 				return error_with_patch(r,
 							item->commit,
-							item->arg,
-							item->arg_len, opts,
-							res, 0);
+							arg, item->arg_len,
+							opts, res, 0);
 		}
 
 		todo_list->current++;
@@ -4267,7 +4430,7 @@ static const char *label_oid(struct object_id *oid, const char *label,
 }
 
 static int make_script_with_merges(struct pretty_print_context *pp,
-				   struct rev_info *revs, FILE *out,
+				   struct rev_info *revs, struct strbuf *out,
 				   unsigned flags)
 {
 	int keep_empty = flags & TODO_LIST_KEEP_EMPTY;
@@ -4412,7 +4575,7 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 	 * gathering commits not yet shown, reversing the list on the fly,
 	 * then outputting that list (labeling revisions as needed).
 	 */
-	fprintf(out, "%s onto\n", cmd_label);
+	strbuf_addf(out, "%s onto\n", cmd_label);
 	for (iter = tips; iter; iter = iter->next) {
 		struct commit_list *list = NULL, *iter2;
 
@@ -4422,9 +4585,9 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 		entry = oidmap_get(&state.commit2label, &commit->object.oid);
 
 		if (entry)
-			fprintf(out, "\n%c Branch %s\n", comment_line_char, entry->string);
+			strbuf_addf(out, "\n%c Branch %s\n", comment_line_char, entry->string);
 		else
-			fprintf(out, "\n");
+			strbuf_addch(out, '\n');
 
 		while (oidset_contains(&interesting, &commit->object.oid) &&
 		       !oidset_contains(&shown, &commit->object.oid)) {
@@ -4437,8 +4600,8 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 		}
 
 		if (!commit)
-			fprintf(out, "%s %s\n", cmd_reset,
-				rebase_cousins ? "onto" : "[new root]");
+			strbuf_addf(out, "%s %s\n", cmd_reset,
+				    rebase_cousins ? "onto" : "[new root]");
 		else {
 			const char *to = NULL;
 
@@ -4451,12 +4614,12 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 					       &state);
 
 			if (!to || !strcmp(to, "onto"))
-				fprintf(out, "%s onto\n", cmd_reset);
+				strbuf_addf(out, "%s onto\n", cmd_reset);
 			else {
 				strbuf_reset(&oneline);
 				pretty_print_commit(pp, commit, &oneline);
-				fprintf(out, "%s %s # %s\n",
-					cmd_reset, to, oneline.buf);
+				strbuf_addf(out, "%s %s # %s\n",
+					    cmd_reset, to, oneline.buf);
 			}
 		}
 
@@ -4465,11 +4628,11 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 			entry = oidmap_get(&commit2todo, oid);
 			/* only show if not already upstream */
 			if (entry)
-				fprintf(out, "%s\n", entry->string);
+				strbuf_addf(out, "%s\n", entry->string);
 			entry = oidmap_get(&state.commit2label, oid);
 			if (entry)
-				fprintf(out, "%s %s\n",
-					cmd_label, entry->string);
+				strbuf_addf(out, "%s %s\n",
+					    cmd_label, entry->string);
 			oidset_insert(&shown, oid);
 		}
 
@@ -4491,13 +4654,11 @@ static int make_script_with_merges(struct pretty_print_context *pp,
 	return 0;
 }
 
-int sequencer_make_script(struct repository *r, FILE *out,
-			  int argc, const char **argv,
-			  unsigned flags)
+int sequencer_make_script(struct repository *r, struct strbuf *out, int argc,
+			  const char **argv, unsigned flags)
 {
 	char *format = NULL;
 	struct pretty_print_context pp = {0};
-	struct strbuf buf = STRBUF_INIT;
 	struct rev_info revs;
 	struct commit *commit;
 	int keep_empty = flags & TODO_LIST_KEEP_EMPTY;
@@ -4540,16 +4701,13 @@ int sequencer_make_script(struct repository *r, FILE *out,
 
 		if (!is_empty && (commit->object.flags & PATCHSAME))
 			continue;
-		strbuf_reset(&buf);
 		if (!keep_empty && is_empty)
-			strbuf_addf(&buf, "%c ", comment_line_char);
-		strbuf_addf(&buf, "%s %s ", insn,
+			strbuf_addf(out, "%c ", comment_line_char);
+		strbuf_addf(out, "%s %s ", insn,
 			    oid_to_hex(&commit->object.oid));
-		pretty_print_commit(&pp, commit, &buf);
-		strbuf_addch(&buf, '\n');
-		fputs(buf.buf, out);
+		pretty_print_commit(&pp, commit, out);
+		strbuf_addch(out, '\n');
 	}
-	strbuf_release(&buf);
 	return 0;
 }
 
@@ -4557,91 +4715,95 @@ int sequencer_make_script(struct repository *r, FILE *out,
  * Add commands after pick and (series of) squash/fixup commands
  * in the todo list.
  */
-int sequencer_add_exec_commands(struct repository *r,
-				const char *commands)
+void todo_list_add_exec_commands(struct todo_list *todo_list,
+				 struct string_list *commands)
 {
-	const char *todo_file = rebase_path_todo();
-	struct todo_list todo_list = TODO_LIST_INIT;
-	struct strbuf *buf = &todo_list.buf;
-	size_t offset = 0, commands_len = strlen(commands);
-	int i, insert;
+	struct strbuf *buf = &todo_list->buf;
+	size_t base_offset = buf->len;
+	int i, insert, nr = 0, alloc = 0;
+	struct todo_item *items = NULL, *base_items = NULL;
+
+	base_items = xcalloc(commands->nr, sizeof(struct todo_item));
+	for (i = 0; i < commands->nr; i++) {
+		size_t command_len = strlen(commands->items[i].string);
+
+		strbuf_addstr(buf, commands->items[i].string);
+		strbuf_addch(buf, '\n');
 
-	if (strbuf_read_file(&todo_list.buf, todo_file, 0) < 0)
-		return error(_("could not read '%s'."), todo_file);
+		base_items[i].command = TODO_EXEC;
+		base_items[i].offset_in_buf = base_offset;
+		base_items[i].arg_offset = base_offset + strlen("exec ");
+		base_items[i].arg_len = command_len - strlen("exec ");
 
-	if (parse_insn_buffer(r, todo_list.buf.buf, &todo_list)) {
-		todo_list_release(&todo_list);
-		return error(_("unusable todo list: '%s'"), todo_file);
+		base_offset += command_len + 1;
 	}
 
 	/*
 	 * Insert <commands> after every pick. Here, fixup/squash chains
 	 * are considered part of the pick, so we insert the commands *after*
 	 * those chains if there are any.
+	 *
+	 * As we insert the exec commands immediatly after rearranging
+	 * any fixups and before the user edits the list, a fixup chain
+	 * can never contain comments (any comments are empty picks that
+	 * have been commented out because the user did not specify
+	 * --keep-empty).  So, it is safe to insert an exec command
+	 * without looking at the command following a comment.
 	 */
-	insert = -1;
-	for (i = 0; i < todo_list.nr; i++) {
-		enum todo_command command = todo_list.items[i].command;
-
-		if (insert >= 0) {
-			/* skip fixup/squash chains */
-			if (command == TODO_COMMENT)
-				continue;
-			else if (is_fixup(command)) {
-				insert = i + 1;
-				continue;
-			}
-			strbuf_insert(buf,
-				      todo_list.items[insert].offset_in_buf +
-				      offset, commands, commands_len);
-			offset += commands_len;
-			insert = -1;
+	insert = 0;
+	for (i = 0; i < todo_list->nr; i++) {
+		enum todo_command command = todo_list->items[i].command;
+		if (insert && !is_fixup(command)) {
+			ALLOC_GROW(items, nr + commands->nr, alloc);
+			COPY_ARRAY(items + nr, base_items, commands->nr);
+			nr += commands->nr;
+
+			insert = 0;
 		}
 
+		ALLOC_GROW(items, nr + 1, alloc);
+		items[nr++] = todo_list->items[i];
+
 		if (command == TODO_PICK || command == TODO_MERGE)
-			insert = i + 1;
+			insert = 1;
 	}
 
 	/* insert or append final <commands> */
-	if (insert >= 0 && insert < todo_list.nr)
-		strbuf_insert(buf, todo_list.items[insert].offset_in_buf +
-			      offset, commands, commands_len);
-	else if (insert >= 0 || !offset)
-		strbuf_add(buf, commands, commands_len);
+	if (insert || nr == todo_list->nr) {
+		ALLOC_GROW(items, nr + commands->nr, alloc);
+		COPY_ARRAY(items + nr, base_items, commands->nr);
+		nr += commands->nr;
+	}
 
-	i = write_message(buf->buf, buf->len, todo_file, 0);
-	todo_list_release(&todo_list);
-	return i;
+	free(base_items);
+	FREE_AND_NULL(todo_list->items);
+	todo_list->items = items;
+	todo_list->nr = nr;
+	todo_list->alloc = alloc;
 }
 
-int transform_todos(struct repository *r, unsigned flags)
+static void todo_list_to_strbuf(struct repository *r, struct todo_list *todo_list,
+				struct strbuf *buf, int num, unsigned flags)
 {
-	const char *todo_file = rebase_path_todo();
-	struct todo_list todo_list = TODO_LIST_INIT;
-	struct strbuf buf = STRBUF_INIT;
 	struct todo_item *item;
-	int i;
-
-	if (strbuf_read_file(&todo_list.buf, todo_file, 0) < 0)
-		return error(_("could not read '%s'."), todo_file);
+	int i, max = todo_list->nr;
 
-	if (parse_insn_buffer(r, todo_list.buf.buf, &todo_list)) {
-		todo_list_release(&todo_list);
-		return error(_("unusable todo list: '%s'"), todo_file);
-	}
+	if (num > 0 && num < max)
+		max = num;
 
-	for (item = todo_list.items, i = 0; i < todo_list.nr; i++, item++) {
+	for (item = todo_list->items, i = 0; i < max; i++, item++) {
 		/* if the item is not a command write it and continue */
 		if (item->command >= TODO_COMMENT) {
-			strbuf_addf(&buf, "%.*s\n", item->arg_len, item->arg);
+			strbuf_addf(buf, "%.*s\n", item->arg_len,
+				    todo_item_get_arg(todo_list, item));
 			continue;
 		}
 
 		/* add command to the buffer */
 		if (flags & TODO_LIST_ABBREVIATE_CMDS)
-			strbuf_addch(&buf, command_to_char(item->command));
+			strbuf_addch(buf, command_to_char(item->command));
 		else
-			strbuf_addstr(&buf, command_to_string(item->command));
+			strbuf_addstr(buf, command_to_string(item->command));
 
 		/* add commit id */
 		if (item->commit) {
@@ -4651,181 +4813,92 @@ int transform_todos(struct repository *r, unsigned flags)
 
 			if (item->command == TODO_MERGE) {
 				if (item->flags & TODO_EDIT_MERGE_MSG)
-					strbuf_addstr(&buf, " -c");
+					strbuf_addstr(buf, " -c");
 				else
-					strbuf_addstr(&buf, " -C");
+					strbuf_addstr(buf, " -C");
 			}
 
-			strbuf_addf(&buf, " %s", oid);
+			strbuf_addf(buf, " %s", oid);
 		}
 
 		/* add all the rest */
 		if (!item->arg_len)
-			strbuf_addch(&buf, '\n');
+			strbuf_addch(buf, '\n');
 		else
-			strbuf_addf(&buf, " %.*s\n", item->arg_len, item->arg);
+			strbuf_addf(buf, " %.*s\n", item->arg_len,
+				    todo_item_get_arg(todo_list, item));
 	}
-
-	i = write_message(buf.buf, buf.len, todo_file, 0);
-	todo_list_release(&todo_list);
-	return i;
 }
 
-enum missing_commit_check_level get_missing_commit_check_level(void)
+int todo_list_write_to_file(struct repository *r, struct todo_list *todo_list,
+			    const char *file, const char *shortrevisions,
+			    const char *shortonto, int num, unsigned flags)
 {
-	const char *value;
-
-	if (git_config_get_value("rebase.missingcommitscheck", &value) ||
-			!strcasecmp("ignore", value))
-		return MISSING_COMMIT_CHECK_IGNORE;
-	if (!strcasecmp("warn", value))
-		return MISSING_COMMIT_CHECK_WARN;
-	if (!strcasecmp("error", value))
-		return MISSING_COMMIT_CHECK_ERROR;
-	warning(_("unrecognized setting %s for option "
-		  "rebase.missingCommitsCheck. Ignoring."), value);
-	return MISSING_COMMIT_CHECK_IGNORE;
-}
+	int res;
+	struct strbuf buf = STRBUF_INIT;
 
-define_commit_slab(commit_seen, unsigned char);
-/*
- * Check if the user dropped some commits by mistake
- * Behaviour determined by rebase.missingCommitsCheck.
- * Check if there is an unrecognized command or a
- * bad SHA-1 in a command.
- */
-int check_todo_list(struct repository *r)
-{
-	enum missing_commit_check_level check_level = get_missing_commit_check_level();
-	struct strbuf todo_file = STRBUF_INIT;
-	struct todo_list todo_list = TODO_LIST_INIT;
-	struct strbuf missing = STRBUF_INIT;
-	int advise_to_edit_todo = 0, res = 0, i;
-	struct commit_seen commit_seen;
+	todo_list_to_strbuf(r, todo_list, &buf, num, flags);
+	if (flags & TODO_LIST_APPEND_TODO_HELP)
+		append_todo_help(flags & TODO_LIST_KEEP_EMPTY, count_commands(todo_list),
+				 shortrevisions, shortonto, &buf);
 
-	init_commit_seen(&commit_seen);
+	res = write_message(buf.buf, buf.len, file, 0);
+	strbuf_release(&buf);
 
-	strbuf_addstr(&todo_file, rebase_path_todo());
-	if (strbuf_read_file_or_whine(&todo_list.buf, todo_file.buf) < 0) {
-		res = -1;
-		goto leave_check;
-	}
-	advise_to_edit_todo = res =
-		parse_insn_buffer(r, todo_list.buf.buf, &todo_list);
+	return res;
+}
 
-	if (res || check_level == MISSING_COMMIT_CHECK_IGNORE)
-		goto leave_check;
+static const char edit_todo_list_advice[] =
+N_("You can fix this with 'git rebase --edit-todo' "
+"and then run 'git rebase --continue'.\n"
+"Or you can abort the rebase with 'git rebase"
+" --abort'.\n");
 
-	/* Mark the commits in git-rebase-todo as seen */
-	for (i = 0; i < todo_list.nr; i++) {
-		struct commit *commit = todo_list.items[i].commit;
-		if (commit)
-			*commit_seen_at(&commit_seen, commit) = 1;
-	}
+int check_todo_list_from_file(struct repository *r)
+{
+	struct todo_list old_todo = TODO_LIST_INIT, new_todo = TODO_LIST_INIT;
+	int res = 0;
 
-	todo_list_release(&todo_list);
-	strbuf_addstr(&todo_file, ".backup");
-	if (strbuf_read_file_or_whine(&todo_list.buf, todo_file.buf) < 0) {
+	if (strbuf_read_file_or_whine(&new_todo.buf, rebase_path_todo()) < 0) {
 		res = -1;
-		goto leave_check;
-	}
-	strbuf_release(&todo_file);
-	res = !!parse_insn_buffer(r, todo_list.buf.buf, &todo_list);
-
-	/* Find commits in git-rebase-todo.backup yet unseen */
-	for (i = todo_list.nr - 1; i >= 0; i--) {
-		struct todo_item *item = todo_list.items + i;
-		struct commit *commit = item->commit;
-		if (commit && !*commit_seen_at(&commit_seen, commit)) {
-			strbuf_addf(&missing, " - %s %.*s\n",
-				    short_commit_name(commit),
-				    item->arg_len, item->arg);
-			*commit_seen_at(&commit_seen, commit) = 1;
-		}
+		goto out;
 	}
 
-	/* Warn about missing commits */
-	if (!missing.len)
-		goto leave_check;
-
-	if (check_level == MISSING_COMMIT_CHECK_ERROR)
-		advise_to_edit_todo = res = 1;
-
-	fprintf(stderr,
-		_("Warning: some commits may have been dropped accidentally.\n"
-		"Dropped commits (newer to older):\n"));
-
-	/* Make the list user-friendly and display */
-	fputs(missing.buf, stderr);
-	strbuf_release(&missing);
-
-	fprintf(stderr, _("To avoid this message, use \"drop\" to "
-		"explicitly remove a commit.\n\n"
-		"Use 'git config rebase.missingCommitsCheck' to change "
-		"the level of warnings.\n"
-		"The possible behaviours are: ignore, warn, error.\n\n"));
-
-leave_check:
-	clear_commit_seen(&commit_seen);
-	strbuf_release(&todo_file);
-	todo_list_release(&todo_list);
+	if (strbuf_read_file_or_whine(&old_todo.buf, rebase_path_todo_backup()) < 0) {
+		res = -1;
+		goto out;
+	}
 
-	if (advise_to_edit_todo)
-		fprintf(stderr,
-			_("You can fix this with 'git rebase --edit-todo' "
-			  "and then run 'git rebase --continue'.\n"
-			  "Or you can abort the rebase with 'git rebase"
-			  " --abort'.\n"));
+	res = todo_list_parse_insn_buffer(r, old_todo.buf.buf, &old_todo);
+	if (!res)
+		res = todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo);
+	if (!res)
+		res = todo_list_check(&old_todo, &new_todo);
+	if (res)
+		fprintf(stderr, _(edit_todo_list_advice));
+out:
+	todo_list_release(&old_todo);
+	todo_list_release(&new_todo);
 
 	return res;
 }
 
-static int rewrite_file(const char *path, const char *buf, size_t len)
-{
-	int rc = 0;
-	int fd = open(path, O_WRONLY | O_TRUNC);
-	if (fd < 0)
-		return error_errno(_("could not open '%s' for writing"), path);
-	if (write_in_full(fd, buf, len) < 0)
-		rc = error_errno(_("could not write to '%s'"), path);
-	if (close(fd) && !rc)
-		rc = error_errno(_("could not close '%s'"), path);
-	return rc;
-}
-
 /* skip picking commits whose parents are unchanged */
-static int skip_unnecessary_picks(struct repository *r, struct object_id *output_oid)
+static int skip_unnecessary_picks(struct repository *r,
+				  struct todo_list *todo_list,
+				  struct object_id *base_oid)
 {
-	const char *todo_file = rebase_path_todo();
-	struct strbuf buf = STRBUF_INIT;
-	struct todo_list todo_list = TODO_LIST_INIT;
 	struct object_id *parent_oid;
-	int fd, i;
-
-	if (!read_oneliner(&buf, rebase_path_onto(), 0))
-		return error(_("could not read 'onto'"));
-	if (get_oid(buf.buf, output_oid)) {
-		strbuf_release(&buf);
-		return error(_("need a HEAD to fixup"));
-	}
-	strbuf_release(&buf);
-
-	if (strbuf_read_file_or_whine(&todo_list.buf, todo_file) < 0)
-		return -1;
-	if (parse_insn_buffer(r, todo_list.buf.buf, &todo_list) < 0) {
-		todo_list_release(&todo_list);
-		return -1;
-	}
+	int i;
 
-	for (i = 0; i < todo_list.nr; i++) {
-		struct todo_item *item = todo_list.items + i;
+	for (i = 0; i < todo_list->nr; i++) {
+		struct todo_item *item = todo_list->items + i;
 
 		if (item->command >= TODO_NOOP)
 			continue;
 		if (item->command != TODO_PICK)
 			break;
 		if (parse_commit(item->commit)) {
-			todo_list_release(&todo_list);
 			return error(_("could not parse commit '%s'"),
 				oid_to_hex(&item->commit->object.oid));
 		}
@@ -4834,137 +4907,103 @@ static int skip_unnecessary_picks(struct repository *r, struct object_id *output
 		if (item->commit->parents->next)
 			break; /* merge commit */
 		parent_oid = &item->commit->parents->item->object.oid;
-		if (!oideq(parent_oid, output_oid))
+		if (!oideq(parent_oid, base_oid))
 			break;
-		oidcpy(output_oid, &item->commit->object.oid);
+		oidcpy(base_oid, &item->commit->object.oid);
 	}
 	if (i > 0) {
-		int offset = get_item_line_offset(&todo_list, i);
 		const char *done_path = rebase_path_done();
 
-		fd = open(done_path, O_CREAT | O_WRONLY | O_APPEND, 0666);
-		if (fd < 0) {
-			error_errno(_("could not open '%s' for writing"),
-				    done_path);
-			todo_list_release(&todo_list);
-			return -1;
-		}
-		if (write_in_full(fd, todo_list.buf.buf, offset) < 0) {
+		if (todo_list_write_to_file(r, todo_list, done_path, NULL, NULL, i, 0)) {
 			error_errno(_("could not write to '%s'"), done_path);
-			todo_list_release(&todo_list);
-			close(fd);
 			return -1;
 		}
-		close(fd);
 
-		if (rewrite_file(rebase_path_todo(), todo_list.buf.buf + offset,
-				 todo_list.buf.len - offset) < 0) {
-			todo_list_release(&todo_list);
-			return -1;
-		}
+		MOVE_ARRAY(todo_list->items, todo_list->items + i, todo_list->nr - i);
+		todo_list->nr -= i;
+		todo_list->current = 0;
 
-		todo_list.current = i;
-		if (is_fixup(peek_command(&todo_list, 0)))
-			record_in_rewritten(output_oid, peek_command(&todo_list, 0));
+		if (is_fixup(peek_command(todo_list, 0)))
+			record_in_rewritten(base_oid, peek_command(todo_list, 0));
 	}
 
-	todo_list_release(&todo_list);
-
 	return 0;
 }
 
 int complete_action(struct repository *r, struct replay_opts *opts, unsigned flags,
 		    const char *shortrevisions, const char *onto_name,
-		    const char *onto, const char *orig_head, const char *cmd,
-		    unsigned autosquash)
+		    struct commit *onto, const char *orig_head,
+		    struct string_list *commands, unsigned autosquash,
+		    struct todo_list *todo_list)
 {
 	const char *shortonto, *todo_file = rebase_path_todo();
-	struct todo_list todo_list = TODO_LIST_INIT;
-	struct strbuf *buf = &(todo_list.buf);
-	struct object_id oid;
-	struct stat st;
+	struct todo_list new_todo = TODO_LIST_INIT;
+	struct strbuf *buf = &todo_list->buf;
+	struct object_id oid = onto->object.oid;
+	int res;
 
-	get_oid(onto, &oid);
 	shortonto = find_unique_abbrev(&oid, DEFAULT_ABBREV);
 
-	if (!lstat(todo_file, &st) && st.st_size == 0 &&
-	    write_message("noop\n", 5, todo_file, 0))
-		return -1;
+	if (buf->len == 0) {
+		struct todo_item *item = append_new_todo(todo_list);
+		item->command = TODO_NOOP;
+		item->commit = NULL;
+		item->arg_len = item->arg_offset = item->flags = item->offset_in_buf = 0;
+	}
 
-	if (autosquash && rearrange_squash(r))
+	if (autosquash && todo_list_rearrange_squash(todo_list))
 		return -1;
 
-	if (cmd && *cmd)
-		sequencer_add_exec_commands(r, cmd);
-
-	if (strbuf_read_file(buf, todo_file, 0) < 0)
-		return error_errno(_("could not read '%s'."), todo_file);
-
-	if (parse_insn_buffer(r, buf->buf, &todo_list)) {
-		todo_list_release(&todo_list);
-		return error(_("unusable todo list: '%s'"), todo_file);
-	}
+	if (commands->nr)
+		todo_list_add_exec_commands(todo_list, commands);
 
-	if (count_commands(&todo_list) == 0) {
+	if (count_commands(todo_list) == 0) {
 		apply_autostash(opts);
 		sequencer_remove_state(opts);
-		todo_list_release(&todo_list);
 
 		return error(_("nothing to do"));
 	}
 
-	strbuf_addch(buf, '\n');
-	strbuf_commented_addf(buf, Q_("Rebase %s onto %s (%d command)",
-				      "Rebase %s onto %s (%d commands)",
-				      count_commands(&todo_list)),
-			      shortrevisions, shortonto, count_commands(&todo_list));
-	append_todo_help(0, flags & TODO_LIST_KEEP_EMPTY, buf);
-
-	if (write_message(buf->buf, buf->len, todo_file, 0)) {
-		todo_list_release(&todo_list);
+	res = edit_todo_list(r, todo_list, &new_todo, shortrevisions,
+			     shortonto, flags);
+	if (res == -1)
 		return -1;
-	}
-
-	if (copy_file(rebase_path_todo_backup(), todo_file, 0666))
-		return error(_("could not copy '%s' to '%s'."), todo_file,
-			     rebase_path_todo_backup());
-
-	if (transform_todos(r, flags | TODO_LIST_SHORTEN_IDS))
-		return error(_("could not transform the todo list"));
-
-	strbuf_reset(buf);
-
-	if (launch_sequence_editor(todo_file, buf, NULL)) {
+	else if (res == -2) {
 		apply_autostash(opts);
 		sequencer_remove_state(opts);
-		todo_list_release(&todo_list);
 
 		return -1;
-	}
-
-	strbuf_stripspace(buf, 1);
-	if (buf->len == 0) {
+	} else if (res == -3) {
 		apply_autostash(opts);
 		sequencer_remove_state(opts);
-		todo_list_release(&todo_list);
+		todo_list_release(&new_todo);
 
 		return error(_("nothing to do"));
 	}
 
-	todo_list_release(&todo_list);
+	if (todo_list_parse_insn_buffer(r, new_todo.buf.buf, &new_todo) ||
+	    todo_list_check(todo_list, &new_todo)) {
+		fprintf(stderr, _(edit_todo_list_advice));
+		checkout_onto(r, opts, onto_name, &onto->object.oid, orig_head);
+		todo_list_release(&new_todo);
 
-	if (check_todo_list(r)) {
-		checkout_onto(opts, onto_name, onto, orig_head);
 		return -1;
 	}
 
-	if (transform_todos(r, flags & ~(TODO_LIST_SHORTEN_IDS)))
-		return error(_("could not transform the todo list"));
-
-	if (opts->allow_ff && skip_unnecessary_picks(r, &oid))
+	if (opts->allow_ff && skip_unnecessary_picks(r, &new_todo, &oid)) {
+		todo_list_release(&new_todo);
 		return error(_("could not skip unnecessary pick commands"));
+	}
 
-	if (checkout_onto(opts, onto_name, oid_to_hex(&oid), orig_head))
+	if (todo_list_write_to_file(r, &new_todo, todo_file, NULL, NULL, -1,
+				    flags & ~(TODO_LIST_SHORTEN_IDS))) {
+		todo_list_release(&new_todo);
+		return error_errno(_("could not write '%s'"), todo_file);
+	}
+
+	todo_list_release(&new_todo);
+
+	if (checkout_onto(r, opts, onto_name, &oid, orig_head))
 		return -1;
 
 	if (require_clean_work_tree(r, "rebase", "", 1, 1))
@@ -4997,21 +5036,13 @@ define_commit_slab(commit_todo_item, struct todo_item *);
  * message will have to be retrieved from the commit (as the oneline in the
  * script cannot be trusted) in order to normalize the autosquash arrangement.
  */
-int rearrange_squash(struct repository *r)
+int todo_list_rearrange_squash(struct todo_list *todo_list)
 {
-	const char *todo_file = rebase_path_todo();
-	struct todo_list todo_list = TODO_LIST_INIT;
 	struct hashmap subject2item;
-	int res = 0, rearranged = 0, *next, *tail, i;
+	int rearranged = 0, *next, *tail, i, nr = 0, alloc = 0;
 	char **subjects;
 	struct commit_todo_item commit_todo;
-
-	if (strbuf_read_file_or_whine(&todo_list.buf, todo_file) < 0)
-		return -1;
-	if (parse_insn_buffer(r, todo_list.buf.buf, &todo_list) < 0) {
-		todo_list_release(&todo_list);
-		return -1;
-	}
+	struct todo_item *items = NULL;
 
 	init_commit_todo_item(&commit_todo);
 	/*
@@ -5024,13 +5055,13 @@ int rearrange_squash(struct repository *r)
 	 * be moved to appear after the i'th.
 	 */
 	hashmap_init(&subject2item, (hashmap_cmp_fn) subject2item_cmp,
-		     NULL, todo_list.nr);
-	ALLOC_ARRAY(next, todo_list.nr);
-	ALLOC_ARRAY(tail, todo_list.nr);
-	ALLOC_ARRAY(subjects, todo_list.nr);
-	for (i = 0; i < todo_list.nr; i++) {
+		     NULL, todo_list->nr);
+	ALLOC_ARRAY(next, todo_list->nr);
+	ALLOC_ARRAY(tail, todo_list->nr);
+	ALLOC_ARRAY(subjects, todo_list->nr);
+	for (i = 0; i < todo_list->nr; i++) {
 		struct strbuf buf = STRBUF_INIT;
-		struct todo_item *item = todo_list.items + i;
+		struct todo_item *item = todo_list->items + i;
 		const char *commit_buffer, *subject, *p;
 		size_t subject_len;
 		int i2 = -1;
@@ -5043,7 +5074,6 @@ int rearrange_squash(struct repository *r)
 		}
 
 		if (is_fixup(item->command)) {
-			todo_list_release(&todo_list);
 			clear_commit_todo_item(&commit_todo);
 			return error(_("the script was already rearranged."));
 		}
@@ -5078,7 +5108,7 @@ int rearrange_squash(struct repository *r)
 				 *commit_todo_item_at(&commit_todo, commit2))
 				/* found by commit name */
 				i2 = *commit_todo_item_at(&commit_todo, commit2)
-					- todo_list.items;
+					- todo_list->items;
 			else {
 				/* copy can be a prefix of the commit subject */
 				for (i2 = 0; i2 < i; i2++)
@@ -5091,7 +5121,7 @@ int rearrange_squash(struct repository *r)
 		}
 		if (i2 >= 0) {
 			rearranged = 1;
-			todo_list.items[i].command =
+			todo_list->items[i].command =
 				starts_with(subject, "fixup!") ?
 				TODO_FIXUP : TODO_SQUASH;
 			if (next[i2] < 0)
@@ -5109,10 +5139,8 @@ int rearrange_squash(struct repository *r)
 	}
 
 	if (rearranged) {
-		struct strbuf buf = STRBUF_INIT;
-
-		for (i = 0; i < todo_list.nr; i++) {
-			enum todo_command command = todo_list.items[i].command;
+		for (i = 0; i < todo_list->nr; i++) {
+			enum todo_command command = todo_list->items[i].command;
 			int cur = i;
 
 			/*
@@ -5123,37 +5151,26 @@ int rearrange_squash(struct repository *r)
 				continue;
 
 			while (cur >= 0) {
-				const char *bol =
-					get_item_line(&todo_list, cur);
-				const char *eol =
-					get_item_line(&todo_list, cur + 1);
-
-				/* replace 'pick', by 'fixup' or 'squash' */
-				command = todo_list.items[cur].command;
-				if (is_fixup(command)) {
-					strbuf_addstr(&buf,
-						todo_command_info[command].str);
-					bol += strcspn(bol, " \t");
-				}
-
-				strbuf_add(&buf, bol, eol - bol);
-
+				ALLOC_GROW(items, nr + 1, alloc);
+				items[nr++] = todo_list->items[cur];
 				cur = next[cur];
 			}
 		}
 
-		res = rewrite_file(todo_file, buf.buf, buf.len);
-		strbuf_release(&buf);
+		FREE_AND_NULL(todo_list->items);
+		todo_list->items = items;
+		todo_list->nr = nr;
+		todo_list->alloc = alloc;
 	}
 
 	free(next);
 	free(tail);
-	for (i = 0; i < todo_list.nr; i++)
+	for (i = 0; i < todo_list->nr; i++)
 		free(subjects[i]);
 	free(subjects);
 	hashmap_free(&subject2item, 1);
-	todo_list_release(&todo_list);
 
 	clear_commit_todo_item(&commit_todo);
-	return res;
+
+	return 0;
 }