bug: git name-rev --stdin --no-undefined on detached head

[Erik Cervin Edin <erik@xxxxxxxxxxx>]

Hey all!

I ran into a situation that I think may be a bug
using git name-rev for detached heads.

Steps to reproduce:
Create a detached head
  git checkout --detached
  git commit --allow-empty -m foo

Expected results:
My understanding is that
  git name-rev $(git rev-list -1 HEAD)
  git rev-list -1 HEAD | git name-rev --stdin
should yield the same result.

As well as combining with other flags
like --name-only / --no-undefined

Actual results:
Where this fails as expected
  git name-rev --no-undefined $(git rev-list HEAD)
this just prints the SHA wo failing
  git rev-list -1 HEAD |  git name-rev --stdin --no-undefined

"name-only" is also affected
  git rev-list -1 HEAD |  git name-rev --stdin --name-only
returns the SHA and not the name

Tested on
git version 2.34.1.windows.1
-- 
Erik Cervin-Edin