sequencer: refactor sequencer_add_exec_commands() to work on a todo_list

This refactors sequencer_add_exec_commands() to work on a todo_list to
avoid redundant reads and writes to the disk.

Instead of inserting the `exec' commands between the other commands and
re-parsing the buffer at the end, they are appended to the buffer once,
and a new list of items is created.  Items from the old list are copied
across and new `exec' items are appended when necessary.  This
eliminates the need to reparse the buffer, but this also means we have
to use todo_list_write_to_disk() to write the file.

todo_list_add_exec_commands() and sequencer_add_exec_commands() are
modified to take a string list instead of a string -- one item for each
command.  This makes it easier to insert a new command to the todo list
for each command to execute.

sequencer_add_exec_commands() still reads the todo list from the disk,
as it is needed by rebase -p.

complete_action() still uses sequencer_add_exec_commands() for now.
This will be changed in a future commit.

Signed-off-by: Alban Gruin <alban.gruin@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 73 insertions, 39 deletions

diff --git a/sequencer.c b/sequencer.c
index 99e12c751e..4c076bd183 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -4505,61 +4505,95 @@ 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)
+static 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;
 
-	if (strbuf_read_file(&todo_list.buf, todo_file, 0) < 0)
-		return error(_("could not read '%s'."), todo_file);
+	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);
 
-	if (todo_list_parse_insn_buffer(r, todo_list.buf.buf, &todo_list)) {
-		todo_list_release(&todo_list);
-		return error(_("unusable todo list: '%s'"), todo_file);
+		strbuf_addstr(buf, commands->items[i].string);
+		strbuf_addch(buf, '\n');
+
+		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 ");
+
+		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;
+	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;
 
-		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;
 		}
 
+		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;
+	}
+
+	free(base_items);
+	FREE_AND_NULL(todo_list->items);
+	todo_list->items = items;
+	todo_list->nr = nr;
+	todo_list->alloc = alloc;
+}
 
-	i = write_message(buf->buf, buf->len, todo_file, 0);
+int sequencer_add_exec_commands(struct repository *r,
+				struct string_list *commands)
+{
+	const char *todo_file = rebase_path_todo();
+	struct todo_list todo_list = TODO_LIST_INIT;
+	int res;
+
+	if (strbuf_read_file(&todo_list.buf, todo_file, 0) < 0)
+		return error_errno(_("could not read '%s'."), todo_file);
+
+	if (todo_list_parse_insn_buffer(r, todo_list.buf.buf, &todo_list)) {
+		todo_list_release(&todo_list);
+		return error(_("unusable todo list: '%s'"), todo_file);
+	}
+
+	todo_list_add_exec_commands(&todo_list, commands);
+	res = todo_list_write_to_file(r, &todo_list, todo_file, NULL, NULL, -1, 0);
 	todo_list_release(&todo_list);
-	return i;
+
+	if (res)
+		return error_errno(_("could not write '%s'."), todo_file);
+	return 0;
 }
 
 static void todo_list_to_strbuf(struct repository *r, struct todo_list *todo_list,
@@ -4790,7 +4824,7 @@ static int skip_unnecessary_picks(struct repository *r, struct object_id *output
 
 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,
+		    const char *onto, const char *orig_head, struct string_list *commands,
 		    unsigned autosquash)
 {
 	const char *shortonto, *todo_file = rebase_path_todo();
@@ -4809,8 +4843,8 @@ int complete_action(struct repository *r, struct replay_opts *opts, unsigned fla
 	if (autosquash && rearrange_squash(r))
 		return -1;
 
-	if (cmd && *cmd)
-		sequencer_add_exec_commands(r, cmd);
+	if (commands->nr)
+		sequencer_add_exec_commands(r, commands);
 
 	if (strbuf_read_file(buf, todo_file, 0) < 0)
 		return error_errno(_("could not read '%s'."), todo_file);