$ git clone -n https://src.fedoraproject.org/rpms/rubygem-rack-test.git /var/lib/mock/f45-build-35208-694/root/chroot_tmpdir/scmroot/rubygem-rack-test
Cloning into '/var/lib/mock/f45-build-35208-694/root/chroot_tmpdir/scmroot/rubygem-rack-test'...
$ git fetch origin 3cd4a5982ae01920d32365c13d242999f37f8466:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-rack-test
 * [new ref]         3cd4a5982ae01920d32365c13d242999f37f8466 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3cd4a59 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild