$ git clone -n https://src.fedoraproject.org/rpms/rubygem-introspection.git /var/lib/mock/f45-build-35027-693/root/chroot_tmpdir/scmroot/rubygem-introspection
Cloning into '/var/lib/mock/f45-build-35027-693/root/chroot_tmpdir/scmroot/rubygem-introspection'...
$ git fetch origin 4a18cf47193c8a17ace093c87319cc0571fa3514:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-introspection
 * [new ref]         4a18cf47193c8a17ace093c87319cc0571fa3514 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 4a18cf4 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild