Re: [PATCH v3 2/2] worktree add: add --orphan flag

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

On Sat, Nov 19 2022, Jacob Abel wrote:

> On 22/11/15 11:35PM, Ævar Arnfjörð Bjarmason wrote:
>>
>> On Tue, Nov 15 2022, Eric Sunshine wrote:
>>
>> > On Tue, Nov 15, 2022 at 4:13 PM Ævar Arnfjörð Bjarmason
>> > <avarab@gmail.com> wrote:
>> >> On Thu, Nov 10 2022, Jacob Abel wrote:
>> >> > Adds support for creating an orphan branch when adding a new worktree.
>> >> > This functionality is equivalent to git switch's --orphan flag.
>> >> >
>> >> > The original reason this feature was implemented was to allow a user
>> >> > to initialise a new repository using solely the worktree oriented
>> >> > workflow. Example usage included below.
>> >> >
>> >> > $ GIT_DIR=".git" git init --bare
>> >> > $ git worktree add --orphan master master/
>> >> >
>> >> > Signed-off-by: Jacob Abel <jacobabel@nullpo.dev>
>> >> > ---
>> >> > +Create a worktree containing an orphan branch named `<branch>` with a
>> >> > +clean working directory.  See `--orphan` in linkgit:git-switch[1] for
>> >> > +more details.
>> >>
>> >> Seeing as "git switch" is still marked "EXPERIMENTAL", it may be prudent
>> >> in general to avoid linking to it in lieu of "git checkout".
>> >>
>> >> In this case in particular though the "more details" are almost
>> >> completely absent from the "git-switch" docs, and they don't (which is
>> >> their won flaw) link to the more detailed "git-checkout" docs.
>> >>
>> >> But for this patch, it seems much better to link to the "checkout" docs,
>> >> no?
>> >
>> > Sorry, no. The important point here is that the --orphan option being
>> > added to `git worktree add` closely follows the behavior of `git
>> > switch --orphan`, which is quite different from the behavior of `git
>> > checkout --orphan`.
>> >
>> > The `git switch --orphan` documentation doesn't seem particularly
>> > lacking; it correctly describes the (very) simplified behavior of that
>> > command over `git checkout --orphan`. I might agree that there isn't
>> > much reason to link to git-switch for "more details", though, since
>> > there isn't really anything else that needs to be said.
>>
>> Aside from what it says now: 1/2 of what I'm saying is that linking to
>> it while it says it's "EXPERIMENTAL" might be either jumping the gun.
>>
>> Or maybe we should just declare it non-"EXPERIMENTAL", but in any case
>> this unrelated topic might want to avoid that altogether and just link
>> to the "checkout" version.
>>
>> A quick grep of our docs (for linkgit:git-switch) that this would be the
>> first mention outside of user-manual.txt where we link to it when it's
>> not in the context of "checkout or switch", or where we're explaining
>> something switch-specific (i.e. the "suggestDetachingHead" advice).
>>
>> Having said that I don't really care, just a suggestion...
>>
>> > If we did want to say something else here, we might copy one sentence
>> > from the `git checkout --orphan` documentation:
>> >
>> >     The first commit made on this new branch will have no parents and
>> >     it will be the root of a new history totally disconnected from all
>> >     the other branches and commits.
>> >
>> > The same sentence could be added to `git switch --orphan`
>> > documentation, but that's outside the scope of this patch series (thus
>> > can be done later by someone).
>>
>> I think I was partially confused by skimming the SYNOPSIS and thinking
>> this supported <start-point> like checkout, which as I found in
>> https://lore.kernel.org/git/221115.86edu3kfqz.gmgdl@evledraar.gmail.com/
>> just seems to be a missing assertion where we want to die() if that's
>> provided in this mode.
>>
>> What I also found a bit confusing (but maybe it's just me) is that the
>> "with a clean working directory" seemed at first to be drawing a
>> distinction between this behavior and that of "git switch", but from
>> poking at it some more it seems to be expressing "this is like git
>> switch's --orphan" with that.
>>
>> I think instead of "clean working tree" it would be better to talk about
>> "tracked files", as "git switch --orphan" does, which AFAICT is what it
>> means. But then again the reason "switch" does that is because you have
>> *existing* tracked files, which inherently doesn't apply for "worktree".
>>
>> Hrm.
>>
>> So, I guess it depends on your mental model of this operation, but at
>> least I think it's more intuitive to explain it in terms of "git
>> checkout --orphan", not "git switch --orphan". I.e.:
>>
>> 	Create a worktree containing an orphan branch named
>> 	`<branch>`. This works like linkgit:git-checkout[1]'s `--orphan'
>> 	option, except '<start-point>` isn't supported, and the "clear
>> 	the index" doesn't apply (as "worktree add" will always have a
>> 	new index)".
>>
>> Whereas defining this in terms of git-switch's "All tracked files are
>> removed" might just be more confusing. What files? Since it's "worktree
>> add" there weren't any in the first place.
>>
>> Anyway, I don't mind it as it is, but maybe the above write-up helps for
>> #leftoverbits if we ever want to unify these docs. I.e. AFAICT we could:
>>
>>  * Link from git-worktree to git-checkout, saying the above
>>  * Link from git-switch to git-checkout, ditto, but that we also "remove
>>    tracked files [of the current HEAD]".
>
> Apologies for the mistake in the SYNOPSIS. As mentioned in the other replies
> I've updated it as you indicated to correct that.
>
> As for a path forwards on the referencing of either git-checkout or git-switch
> from git-worktree, I think I'm leaning towards Eric's approach (in his reply
> to this message) where we don't reference either and fully outline the
> behavior itself.

Yeah, that makes sense.

>>
>> >> > +test_expect_success '"add" --orphan/-b mutually exclusive' '
>> >> > +     test_must_fail git worktree add --orphan poodle -b poodle bamboo
>> >> > +'
>> >> > +
>> >> > +test_expect_success '"add" --orphan/-B mutually exclusive' '
>> >> > +     test_must_fail git worktree add --orphan poodle -B poodle bamboo
>> >> > +'
>> >> > +
>> >> > +test_expect_success '"add" --orphan/--detach mutually exclusive' '
>> >> > +     test_must_fail git worktree add --orphan poodle --detach bamboo
>> >> > +'
>> >> > +
>> >> > +test_expect_success '"add" --orphan/--no-checkout mutually exclusive' '
>> >> > +     test_must_fail git worktree add --orphan poodle --no-checkout bamboo
>> >> > +'
>> >> > +
>> >> > +test_expect_success '"add" -B/--detach mutually exclusive' '
>> >> > +     test_must_fail git worktree add -B poodle --detach bamboo main
>> >> > +'
>> >> > +
>> >>
>> >> This would be much better as a for-loop:
>> >>
>> >> for opt in -b -B ...
>> >> do
>> >>         test_expect_success "...$opt" '<test here, uses $opt>'
>> >> done
>> >>
>> >> Note the ""-quotes for the description, and '' for the test, that's not
>> >> a mistake, we eval() the latter.
>> >
>> > Such a loop would need to be more complex than this, wouldn't it, to
>> > account for all the combinations? I'd normally agree about the loop,
>> > but given that it requires extra complexity, I don't really mind
>> > seeing the individual tests spelled out manually in this case; they're
>> > dead simple to understand as written. I don't feel strongly either
>> > way, but I also don't want to ask for extra work from the patch author
>> > for a subjective change.
>>
>> Yeah, it's probably not worth it. This is partially cleaning up existing
>> tests, but maybe:
>>
>> 	diff --git a/t/t2400-worktree-add.sh b/t/t2400-worktree-add.sh
>> 	index 93c340f4aff..5acfd48f418 100755
>> 	--- a/t/t2400-worktree-add.sh
>> 	+++ b/t/t2400-worktree-add.sh
>> 	@@ -298,37 +298,21 @@ test_expect_success '"add" no auto-vivify with --detach and <branch> omitted' '
>> 	 	test_must_fail git -C mish/mash symbolic-ref HEAD
>> 	 '
>>
>> 	-test_expect_success '"add" -b/-B mutually exclusive' '
>> 	-	test_must_fail git worktree add -b poodle -B poodle bamboo main
>> 	-'
>> 	-
>> 	-test_expect_success '"add" -b/--detach mutually exclusive' '
>> 	-	test_must_fail git worktree add -b poodle --detach bamboo main
>> 	-'
>> 	-
>> 	-test_expect_success '"add" -B/--detach mutually exclusive' '
>> 	-	test_must_fail git worktree add -B poodle --detach bamboo main
>> 	-'
>> 	-
>> 	-test_expect_success '"add" --orphan/-b mutually exclusive' '
>> 	-	test_must_fail git worktree add --orphan poodle -b poodle bamboo
>> 	-'
>> 	-
>> 	-test_expect_success '"add" --orphan/-B mutually exclusive' '
>> 	-	test_must_fail git worktree add --orphan poodle -B poodle bamboo
>> 	-'
>> 	-
>> 	-test_expect_success '"add" --orphan/--detach mutually exclusive' '
>> 	-	test_must_fail git worktree add --orphan poodle --detach bamboo
>> 	-'
>> 	-
>> 	-test_expect_success '"add" --orphan/--no-checkout mutually exclusive' '
>> 	-	test_must_fail git worktree add --orphan poodle --no-checkout bamboo
>> 	-'
>> 	-
>> 	-test_expect_success '"add" -B/--detach mutually exclusive' '
>> 	-	test_must_fail git worktree add -B poodle --detach bamboo main
>> 	-'
>> 	+test_wt_add_excl() {
>> 	+	local opts="$@" &&
>> 	+	test_expect_success "'worktree add' with '$opts' has mutually exclusive options" '
>> 	+		test_must_fail git worktree add $opts
>> 	+	'
>> 	+}
>> 	+test_wt_add_excl -b poodle -B poodle bamboo main
>> 	+test_wt_add_excl -b poodle --orphan poodle bamboo
>> 	+test_wt_add_excl -b poodle --detach bamboo main
>> 	+test_wt_add_excl -B poodle --detach bamboo main
>> 	+test_wt_add_excl -B poodle --detach bamboo main
>> 	+test_wt_add_excl -B poodle --orphan poodle bamboo
>> 	+test_wt_add_excl --orphan poodle --detach bamboo
>> 	+test_wt_add_excl --orphan poodle --no-checkout bamboo
>> 	+test_wt_add_excl --orphan poodle bamboo main
>>
>> 	 test_expect_success '"add -B" fails if the branch is checked out' '
>> 	 	git rev-parse newmain >before &&
>>
>> I re-arranged that a bit, but probably not worth a loop. I *did* spot in
>> doing that that if I sort the options I end up with a duplicate test,
>> i.e. we test "-B poodle --detach bamboo main" twice.
>>
>> That seems to be added by mistake in 2/2, i.e. it's the existing test
>> you can see in the diff context, just added at the end.
>
> This is much clearer and more succinct. I've applied this to 2/2 for v4.

Great, nice that it helped!