Re: [PATCH 4/4] tag: "git tag" refuses to use HEAD as a tagname

[Jeff King <peff@peff.net>]

On Mon, Dec 02, 2024 at 04:07:14PM +0900, Junio C Hamano wrote:

> Even though the plumbing level allows you to create refs/tags/HEAD
> and refs/heads/HEAD, doing so makes it confusing within the context
> of the UI Git Porcelain commands provides.  Just like we prevent a
> branch from getting called "HEAD" at the Porcelain layer (i.e. "git
> branch" command), teach "git tag" to refuse to create a tag "HEAD".

This looks good and mostly as expected. I do think Rubén's suggestion to
add an explicit deletion test might be worth having to future-proof
things.

> @@ -91,6 +91,12 @@ test_expect_success 'creating a tag using default HEAD should succeed' '
>  	test_must_fail git reflog exists refs/tags/mytag
>  '
>  
> +test_expect_success 'HEAD is forbidden as a tagname' '
> +	test_when_finished "git tag -d HEAD || :" &&
> +	test_must_fail git tag HEAD &&
> +	test_must_fail git tag -a -m "useless" HEAD
> +'

The test_when_finished surprised me a little, just because we would not
expect anything to have been created. I don't think we usually bother
with cleaning up failure modes, as it is a losing battle (if the test
did not succeed you are only guessing at what mess may have been left
behind). But I don't think it's hurting anything, beyond a few wasted
cycles to run what should be a noop.

-Peff