Re: Confusing error message for git switch -d

From: Junio C Hamano <gitster@pobox.com>
Date: Sep 25, 2024, 23:11 UTC
Message-ID: <xmqqr097miqq.fsf@gitster.g>
In-Reply-To: <ce9f0440-e724-4116-b63a-0e62c46c170d@anselmschueler.com>

Anselm Schüler <mail@anselmschueler.com> writes:

Show 9 quoted lines

> I wanted to get the code for CPython 3.12, so I tried running git
> switch -d 3.12, expecting 3.12 to be a tag (which it wasn’t, and it
> was a remote branch).
>
> Git produced this error message:
>
> fatal: '--detach' cannot be used with '-b/-B/--orphan'
>
> This is confusing since I didn’t pass any of these options.

True. FWIW, this is shared between "checkout" and "switch', and I agree that there is a huge room for improvement.

With (arguably overly aggressive for its own worth) the "--guess" option being default, giving the name of a unique remote-tracking branch (that is, "3.12" appears as a remote-tracking branch of only one remote, among possibly multiple remotes you have defined for the repository) would behave as if what you said, which is "3.12", is equivalent to "-b 3.12 --track origin/3.12" (where the "origin" thing is the "only one" remote for which 3.12 exists as a remote-tracking branch). So

    $ git switch --detach 3.12

behaves as if you said

    $ git switch --detach -b 3.12 --track origin/3.12

and the error message is given.

I am merely saying that the mechanism from which this error message is given can be _explained_. I do not think it is well designed, as it does not give a great end-user experience.

Disabling checkout.guess configuration would force you into the habit of being a bit more explicit. Even with checkout.guess configured to false, you can still say

    $ git switch --detach origin/3.12

and because this does not blindly translate to -b/--track, you would not see such an error.

A more appropriate design for "--guess" would be to notice the presence of "--detach" and act differently, i.e. not rewriting blindly 3.12 to "-b 3.12 -t origin/3.12" unconditionally, instead rewrite "--detacu 3.12" to "--detach origin/3.12" if "--detach" is there.

Patches welcome ;-)