Re: New orphan worktree?

From: Eric Sunshine <sunshine@sunshineco.com>
Date: Feb 22, 2021, 23:06 UTC
Message-ID: <CAPig+cSkL+5otKUWwm=CLaRR+j71wW61U7LWtmuUHO+7bZaY_g@mail.gmail.com>
In-Reply-To: <87ft1o8mi0.fsf@evledraar.gmail.com>

On Mon, Feb 22, 2021 at 4:45 AM Ævar Arnfjörð Bjarmason <avarab@gmail.com> wrote:

Show 22 quoted lines

> On Sun, Feb 21 2021, Eric Sunshine wrote:
> > Rather than making --orphan a boolean flag, we'd probably want to
> > mirror the behavior of the other commands and have <branch> be an
> > argument consumed by --orphan:
> >
> >     git worktree add --orphan <branch> <path>
> >
> > That would make --orphan, -b, and -B mutually exclusive, much like
> > they are for git-checkout, and much like -c, -C, and --orphan are
> > mutually exclusive for git-switch.
>
> I see now (but didn't before, I haven't really used "switch" before)
> that that's how it works.
>
> But that doesn't seem to make much sense as a UI, maybe I'm missing
> something but how do you:
>
>     git switch --orphan existing-branch
>
> Just like you can:
>
>     git switch -C existing-branch <start-point>

When responding to your initial email, I noticed this same shortcoming of --orphan in both git-branch and git-switch, and assumed that's why you made it a boolean in combination with -b/-B in "git worktree add". Before writing that email, I did put a bit of thought into how one might support a "force" mode but didn't include my thoughts in the message.

Show 9 quoted lines

> It's actually this exact use-case that prompted me to write the --orphan
> patch. I wanted to create a "meta" orphan branch in my git.git, but had
> an existing local "meta" (from Jeff King) that I'd happened to have
> checked out long ago which I first needed to "git branch -D".
>
> Wouldn't it make more sense for a feature like this & back-compat to
> start with switch's "--orphan" implying "-c", but you could also supply
> "--orphan -C" instead? And in worktree have -b and -B work like they do
> for other branches.

I'm not sure I follow. In git-switch, --orphan does not imply -c even though --orphan also creates a new branch (thus seems to work similar to -c); it is nevertheless mutually-exclusive with -c and -C. The same goes for --orphan in git-branch.

As far as combining --orphan and -C (or -c), I'm not sure how we would arrange that using the existing parse_options() mechanism. It seems too magical and has potential for weird corner cases.

Since git-worktree doesn't yet support --orphan, we certainly have more leeway and could go with your proposal of having --orphan be boolean and always requiring it to be used in conjunction with -b/-B. However, I'm quite hesitant to take that approach since it breaks with existing precedent in git-branch and git-switch, in which case --orphan takes its own argument (<branch>) and is mutually-exclusive with -b/-B/-c/-C.

When I was pondering the issue before writing my original response, two thoughts came to mind. (1) "git worktree add --force --orphan <branch>" would be one way to make your case work; (2) given how infrequently --orphan is used, we just punt and require people to first use "git branch -D <branch>" if necessary (which has been the status-quo for git-branch and git-switch). The latter thought is superficially tempting, though it doesn't help in automation situations since "git branch -D <branch>" errors out if <branch> doesn't exist, so a script would first have to check for existence of <branch> before attempting to delete it prior to using "git worktree add --orphan <branch>".

So, I don't have any great answers at this time.