$ git clone -n https://src.fedoraproject.org/rpms/rubygem-sprockets.git /var/lib/mock/f38-build-side-42-init-devel-679488-26707/root/chroot_tmpdir/scmroot/rubygem-sprockets
Cloning into '/var/lib/mock/f38-build-side-42-init-devel-679488-26707/root/chroot_tmpdir/scmroot/rubygem-sprockets'...
$ git fetch origin 3cd71621793d4d73e0c9a2b36fb7bad511bd6144:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-sprockets
 * [new ref]         3cd71621793d4d73e0c9a2b36fb7bad511bd6144 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3cd7162 Remove unneded `rubygem(coffee-script)` require.