On Wed, Oct 25, 2023 at 03:44:33PM +0100, Phillip Wood wrote:

On 25/10/2023 15:26, Han-Wen Nienhuys wrote:

quoted

On Tue, Oct 24, 2023 at 9:17 PM Junio C Hamano [off-list ref] wrote:

quoted

Patrick Steinhardt [off-list ref] writes:

quoted

this patch series introduces a new `--exists` mode to git-show-ref(1) to
explicitly check for the existence of a reference, only.

I agree that show-ref would be the best place for this feature (not
rev-parse, which is already a kitchen sink).  After all, the command
was designed for validating refs in 358ddb62 (Add "git show-ref"
builtin command, 2006-09-15).

Thanks.  Hopefully I can take a look before I go offline.

The series description doesn't say why users would care about this.

If this is just to ease testing, I suggest adding functionality to a
suitable test helper. Anything you add to git-show-ref is a publicly
visible API that needs documentation and comes with a stability
guarantee that is more expensive to maintain than test helper
functionality.

Does the new functionality provide a way for scripts to see if a branch is
unborn (i.e. has not commits yet)? I don't think we have a way to
distinguish between a ref that points to a missing object and an unborn
branch at the moment.

You could do it with two commands:

target=$(git symbolic-ref HEAD)
git show-ref --exists "$target"
case "$?" in
2)
    echo "unborn branch";;
0)
    echo "branch exists";;
*)
    echo "could be anything, dunno";;
esac

While you could use git-rev-parse(1) instead of git-show-ref(1), you
wouldn't be able to easily distinguish the case of a missing target
reference and any other kind of error.

Patrick