Re: New orphan worktree?

On Mon, Feb 22, 2021 at 4:45 AM Ævar Arnfjörð Bjarmason
[off-list ref] wrote:

On Sun, Feb 21 2021, Eric Sunshine wrote:

quoted

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.

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.