Re: New orphan worktree?

On Sun, Feb 21 2021, Eric Sunshine wrote:

On Wed, Feb 17, 2021 at 8:26 PM Ævar Arnfjörð Bjarmason
[off-list ref] wrote:

quoted

On Wed, Jan 06 2021, Eric Sunshine wrote:

quoted

Yep, when/if --orphan is added to `git worktree add`, it should mimic
the behavior of --orphan in git-switch rather than git-checkout.

How would a mode for "worktree add --orphan" that mimics checkout rather
than switch even look like? The "checkout --orphan" special-case is
because we retain the index, so you need to "git rm -rf .".

But with worktrees we always get a new index, so AFAICT the only way to
make it work like "checkout" would be to have it be the only mode that
copies over the current worktree's index.

I hadn't actually put any thought into it aside from (1) `--orphan`
being a likely candidate for `git worktree add`, and (2) my uses of
orphan branches always involved `git checkout --orphan && git rm -rf
.`. I never got as far as thinking about the actual implementation.

quoted

In any case I implemented a rough version of this today, and it uses the
"switch" semantics. I only discovered this ML thread afterwards.

It's surely full of bugs, and needs test work (see all the BUG(...)),
but if someone's interested in taking it further all it should need is
some more tests & dealing with the edge cases of incompatible options
etc. It's Signed-off-by: Ævar Arnfjörð Bjarmason [off-list ref].

Thanks. This looks like a good start.

quoted

+test_expect_success '"add" worktree orphan branch' '
+       git worktree add --orphan -b orphan here-orphan &&

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>

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.