$ git clone -n https://src.fedoraproject.org/rpms/rubygem-gist.git /var/lib/mock/f45-build-34937-692/root/chroot_tmpdir/scmroot/rubygem-gist
Cloning into '/var/lib/mock/f45-build-34937-692/root/chroot_tmpdir/scmroot/rubygem-gist'...
$ git fetch origin 16d2be6f4db391512412a1380ba85f0e15800f60:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-gist
 * [new ref]         16d2be6f4db391512412a1380ba85f0e15800f60 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 16d2be6 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild