$ git clone -n https://src.fedoraproject.org/rpms/gcr3.git /var/lib/mock/f45-build-9646-407/root/chroot_tmpdir/scmroot/gcr3
Cloning into '/var/lib/mock/f45-build-9646-407/root/chroot_tmpdir/scmroot/gcr3'...
$ git fetch origin e893cfa064b61ec8d9ab22d86ad08f37bda3e0e8:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gcr3
 * [new ref]         e893cfa064b61ec8d9ab22d86ad08f37bda3e0e8 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e893cfa Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild