Re: [PATCH v2 2/2] rebase --exec: make it work with --rebase-merges

> 
> From: Johannes Schindelin <johannes.schindelin@gmx.de>
> 
> The idea of `--exec` is to append an `exec` call after each `pick`.
> 
> Since the introduction of fixup!/squash! commits, this idea was extended
> to apply to "pick, possibly followed by a fixup/squash chain", i.e. an
> exec would not be inserted between a `pick` and any of its corresponding
> `fixup` or `squash` lines.
> 
> The current implementation uses a dirty trick to achieve that: it
> assumes that there are only pick/fixup/squash commands, and then
> *inserts* the `exec` lines before any `pick` but the first, and appends
> a final one.
> 
> With the todo lists generated by `git rebase --rebase-merges`, this
> simple implementation shows its problems: it produces the exact wrong
> thing when there are `label`, `reset` and `merge` commands.
> 
> Let's change the implementation to do exactly what we want: look for
> `pick` lines, skip any fixup/squash chains, and then insert the `exec`
> line. Lather, rinse, repeat.
> 
> While at it, also add `exec` lines after `merge` commands, because they
> are similar in spirit to `pick` commands: they add new commits.
> 
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
> ---
>   sequencer.c              | 37 +++++++++++++++++++++++++++----------
>   t/t3430-rebase-merges.sh |  2 +-
>   2 files changed, 28 insertions(+), 11 deletions(-)
> 
> diff --git a/sequencer.c b/sequencer.c
> index 31038472f..ed2e694ff 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -4244,10 +4244,9 @@ int sequencer_add_exec_commands(const char *commands)
>   {
>   	const char *todo_file = rebase_path_todo();
>   	struct todo_list todo_list = TODO_LIST_INIT;
> -	struct todo_item *item;
>   	struct strbuf *buf = &todo_list.buf;
>   	size_t offset = 0, commands_len = strlen(commands);
> -	int i, first;
> +	int i, insert;
>   
>   	if (strbuf_read_file(&todo_list.buf, todo_file, 0) < 0)
>   		return error(_("could not read '%s'."), todo_file);
> @@ -4257,19 +4256,37 @@ int sequencer_add_exec_commands(const char *commands)
>   		return error(_("unusable todo list: '%s'"), todo_file);
>   	}
>   
> -	first = 1;
> -	/* insert <commands> before every pick except the first one */
> -	for (item = todo_list.items, i = 0; i < todo_list.nr; i++, item++) {
> -		if (item->command == TODO_PICK && !first) {
> -			strbuf_insert(buf, item->offset_in_buf + offset,
> -				      commands, commands_len);
> +	/*
> +	 * 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.
> +	 */
> +	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;
>   		}
> -		first = 0;
> +
> +		if (command == TODO_PICK || command == TODO_MERGE)
> +			insert = i + 1;
>   	}
>   
>   	/* append final <commands> */
> -	strbuf_add(buf, commands, commands_len);
> +	if (insert >= 0 || !offset)
> +		strbuf_add(buf, commands, commands_len);

>   
>   	i = write_message(buf->buf, buf->len, todo_file, 0);
>   	todo_list_release(&todo_list);
> diff --git a/t/t3430-rebase-merges.sh b/t/t3430-rebase-merges.sh
> index 0bf5eaa37..90ae613e2 100755
> --- a/t/t3430-rebase-merges.sh
> +++ b/t/t3430-rebase-merges.sh
> @@ -363,7 +363,7 @@ test_expect_success 'octopus merges' '
>   	EOF
>   '
>   
> -test_expect_failure 'with --autosquash and --exec' '
> +test_expect_success 'with --autosquash and --exec' '
>   	git checkout -b with-exec H &&
>   	echo Booh >B.t &&
>   	test_tick &&
>