Re: [PATCH] sequencer: rectify empty hint in call of require_clean_work_tree()

Oswald Buddenhagen <oswald.buddenhagen@gmx.de> writes:

I won't repeat what Peff already said on another ping! we saw recently on the list.

The call to require_clean_work_tree() with "" hint existed ever since this part of the "rebase" machinery was rewritten in C by b97e1873 (rebase -i: rewrite complete_action() in C, 2018-08-28). I added the author of that change to the Cc: list.

The original implementation of require_clean_work_tree looked like this:

require_clean_work_tree () {
	git rev-parse --verify HEAD >/dev/null || exit 1
	git update-index -q --ignore-submodules --refresh
	err=0

	if ! git diff-files --quiet --ignore-submodules
	then
		...
		err=1
	fi

	if ! git diff-index --cached --quiet --ignore-submodules HEAD --
	then
		...
		err=1
	fi

	if test $err = 1
	then
		test -n "$2" && echo "$2" >&2
		exit 1
	fi
}

I.e. the second argument, "hint", is shown only when it was a non-empty string. It did not add "error:" prefix before the message.

In contrast, this is what wt-status.c has:

int require_clean_work_tree(struct repository *r,
			    const char *action,
			    const char *hint,
			    int ignore_submodules,
			    int gently)
{
	struct lock_file lock_file = LOCK_INIT;
	int err = 0, fd;

	...
	if (err) {
		if (hint)
			error("%s", hint);
		if (!gently)
			exit(128);
	}

	return err;
}

Arguably, using error() as a replacement for 'echo "$2" >&2' was a sloppy conversion made back in ea63b393 (pull: make code more similar to the shell script again, 2016-10-07), but I suspect that in-tree callers that do have something to say, and the end-users who are used to see the messages these callers produce, expect to see the "error:" prefix these days, so it needs further study if we wanted to "fix" the misuse of error() there. In any case, the observation that motivated your patch is not error() vs fputs().

For squelching a useless "hint" that is empty (other than that mistaken "error:" prefix), however, I think you can and should do better than replacing "" with NULL on the callers' side. As we can see from the comparison between the original, scripted version and the verison in C that is in wt-status.c of require_clean_work_tree, checking for NULL-ness of hint is another misconversion made when it was rewritten in C.

I think the right fix would be more like the attached patch, which will fix any other callsites that pass "" at the same time. Of course, you can fix the callers on top, but that is secondary.

 wt-status.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)