$ git clone -n https://src.fedoraproject.org/rpms/rubygem-gdk3.git /var/lib/mock/f39-build-1596784-38402/root/chroot_tmpdir/scmroot/rubygem-gdk3
Cloning into '/var/lib/mock/f39-build-1596784-38402/root/chroot_tmpdir/scmroot/rubygem-gdk3'...
$ git fetch origin bd0f68871fca358c68798a5ff2af67c1bc109750:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-gdk3
 * [new ref]         bd0f68871fca358c68798a5ff2af67c1bc109750 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at bd0f688 4.2.0 entry