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

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

On Thu, Nov 10 2022, Jacob Abel wrote:

So, on a second read-through...

>  'git worktree add' [-f] [--detach] [--checkout] [--lock [--reason <string>]]
> -		   [[-b | -B] <new-branch>] <path> [<commit-ish>]
> +		   [[-b | -B | --orphan] <new-branch>] <path> [<commit-ish>]

This synopsis is now at least partially wrong, and ....

> +--orphan <new-branch>::
> +	With `add`, create a new orphan branch named `<new-branch>` in the new
> +	worktree. See `--orphan` in linkgit:git-switch[1] for details.
> +
>  --porcelain::
> ....
>  #define BUILTIN_WORKTREE_ADD_USAGE \
>  	N_("git worktree add [-f] [--detach] [--checkout] [--lock [--reason <string>]]\n" \
> -	   "                 [[-b | -B] <new-branch>] <path> [<commit-ish>]")
> +	   "                 [[-b | -B | --orphan] <new-branch>] <path> [<commit-ish>]")


...here we say the same, but surely it's only:

	git worktree add --orphan new-branch /tmp/orphan

And not e.g.:

	git worktree add --orphan new-branch /tmp/orphan origin/next

Or whatever, but it's incompatible with <commit-ish>. I think this on
top should fix it up:
	
	diff --git a/Documentation/git-worktree.txt b/Documentation/git-worktree.txt
	index 1310bfb564f..3afef985154 100644
	--- a/Documentation/git-worktree.txt
	+++ b/Documentation/git-worktree.txt
	@@ -10,7 +10,9 @@ SYNOPSIS
	 --------
	 [verse]
	 'git worktree add' [-f] [--detach] [--checkout] [--lock [--reason <string>]]
	-		   [[-b | -B | --orphan] <new-branch>] <path> [<commit-ish>]
	+		   [[-b | -B] <new-branch>] <path> [<commit-ish>]
	+'git worktree add' [-f] [--lock [--reason <string>]]
	+		   --orphan <new-branch> <path>
	 'git worktree list' [-v | --porcelain [-z]]
	 'git worktree lock' [--reason <string>] <worktree>
	 'git worktree move' <worktree> <new-path>
	diff --git a/builtin/worktree.c b/builtin/worktree.c
	index 71786b72f6b..2b811630b3a 100644
	--- a/builtin/worktree.c
	+++ b/builtin/worktree.c
	@@ -17,7 +17,10 @@
	 
	 #define BUILTIN_WORKTREE_ADD_USAGE \
	 	N_("git worktree add [-f] [--detach] [--checkout] [--lock [--reason <string>]]\n" \
	-	   "                 [[-b | -B | --orphan] <new-branch>] <path> [<commit-ish>]")
	+	   "                 [[-b | -B] <new-branch>] <path> [<commit-ish>]"), \
	+	N_("git worktree add [-f] [--lock [--reason <string>]]\n" \
	+	   "                 --orphan <new-branch> <path>")
	+
	 #define BUILTIN_WORKTREE_LIST_USAGE \
	 	N_("git worktree list [-v | --porcelain [-z]]")
	 #define BUILTIN_WORKTREE_LOCK_USAGE \
	@@ -668,6 +671,9 @@ static int add(int ac, const char **av, const char *prefix)
	 	if (opts.orphan_branch && !opts.checkout)
	 		die(_("'%s' and '%s' cannot be used together"), "--orphan",
	 		    "--no-checkout");
	+	if (opts.orphan_branch && ac == 2)
	+		die(_("'%s' and '%s' cannot be used together"), "--orphan",
	+		    _("<commit-ish>"));
	 	if (lock_reason && !keep_locked)
	 		die(_("the option '%s' requires '%s'"), "--reason", "--lock");
	 	if (lock_reason)
	diff --git a/t/t2400-worktree-add.sh b/t/t2400-worktree-add.sh
	index 93c340f4aff..47461d02115 100755
	--- a/t/t2400-worktree-add.sh
	+++ b/t/t2400-worktree-add.sh
	@@ -326,6 +326,10 @@ test_expect_success '"add" --orphan/--no-checkout mutually exclusive' '
	 	test_must_fail git worktree add --orphan poodle --no-checkout bamboo
	 '
	 
	+test_expect_success '"add" --orphan and <commit-ish> mutually exclusive' '
	+	test_must_fail git worktree add --orphan poodle bamboo main
	+'
	+
	 test_expect_success '"add" -B/--detach mutually exclusive' '
	 	test_must_fail git worktree add -B poodle --detach bamboo main
	 '

> -	if (ac < 2 && !new_branch && !opts.detach) {
> +	/*
> +	 * As the orphan cannot be created until the contents of branch
> +	 * are staged, opts.orphan_branch should be treated as both a boolean
> +	 * indicating that `--orphan` was selected and as the name of the new
> +	 * orphan branch from this point on.
> +	 */

I've re-read this a couple of times, and I honestly still don't see what
point is trying to drive home.

So, "--orphan" is an OPT_STRING(), so it always has a value:

	$ ./git worktree add --orphan 
	error: option `orphan' requires a value

But we init it to NULL, and above we just used it as a boolean *and*
below.

I.e. this comment would seem to me to fit with code where the reader
might be surprised that we're using "opts.orphan_branch" as a string
from then on, but we're just copying that to "new_branch", then we
always use "opts.orphan_branch" as a boolean for the rest of the
function.

I may be missing something, but I think this would probably be better
just without this comment. E.g. we use "--track", "--lock-reason"
etc. in similar ways, and those don't have a comment like that.


> +	if (opts.orphan_branch) {
> +		new_branch = opts.orphan_branch;
> +	}
> +
> +	if (ac < 2 && !new_branch && !opts.detach && !opts.orphan_branch) {

In general we shouldn't combine random "if"'s just because a a
sufficiently smart compiler could discover a way to reduce work.

But in this case these seem to be inherently connected, we always want
the not-DWIM behavior with "orphan", no?

So shouldn't this just be:

	if (opts.orphan_branch) {
		...
	} else if (ac < 2 && !new_branch && !opts.detach) {
		....
	}

?