Subject: Re: [PATCH] branch: error copying or renaming a detached HEAD

From: Junio C Hamano <[email-masked]>
Date: Tue, 25 Oct 2022 16:50:41 -0700

Rubén Justo <[email-masked]> writes:

> Let's remove the condition in copy_or_rename_branch() (the current
> function name) and check for HEAD before calling it, dying with the
> original intended error if we're in a detached HEAD.

Makes sense.

> @@ -827,24 +820,19 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
>  		strbuf_release(&buf);
>  
>  		return ret;
> -	} else if (copy) {
> -		if (!argc)
> -			die(_("branch name required"));
> -		else if (argc == 1)
> -			copy_or_rename_branch(head, argv[0], 1, copy > 1);
> -		else if (argc == 2)
> -			copy_or_rename_branch(argv[0], argv[1], 1, copy > 1);
> -		else
> -			die(_("too many branches for a copy operation"));
> -	} else if (rename) {
> +	} else if (copy || rename) {
>  		if (!argc)
>  			die(_("branch name required"));
> +		else if ((argc == 1) && filter.detached)
> +			die(copy? _("cannot copy the current branch while not on any.")
> +				: _("cannot rename the current branch while not on any."));

Missing " " before "?".

>  		else if (argc == 1)
> -			copy_or_rename_branch(head, argv[0], 0, rename > 1);
> +			copy_or_rename_branch(head, argv[0], copy, copy + rename > 1);

The third argument being 'copy' makes sense (as the original has 1
for copy and 0 for rename).  As we reject if rename and copy are
both set, here we have either copy > 0 or rename > 0 but not both,
so the fourth argument makes sense, too.

>  		else if (argc == 2)
> -			copy_or_rename_branch(argv[0], argv[1], 0, rename > 1);
> +			copy_or_rename_branch(argv[0], argv[1], copy, copy + rename > 1);
>  		else
> -			die(_("too many arguments for a rename operation"));
> +			die(copy? _("too many branches for a copy operation")
> +				: _("too many arguments for a rename operation"));

Ditto.

> diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
> index 7d8edff9c3..38c57de71b 100755
> --- a/t/t3200-branch.sh
> +++ b/t/t3200-branch.sh
> @@ -268,6 +268,17 @@ test_expect_success 'git branch -M topic topic should work when main is checked
>  	git branch -M topic topic
>  '
>  
> +test_expect_success 'git branch -M and -C fail on detached HEAD' '
> +	git checkout HEAD^{} &&
> +	test_when_finished git checkout - &&
> +	echo "fatal: cannot rename the current branch while not on any." >expect &&
> +	test_must_fail git branch -M must-fail 2>err &&
> +	test_cmp expect err &&
> +	echo "fatal: cannot copy the current branch while not on any." >expect &&
> +	test_must_fail git branch -C must-fail 2>err &&
> +	test_cmp expect err
> +'

Excellent.

I'll do the whitespace tweak while queueing, so there is no need to
resend only to fix them.

Thanks.