$ git clone -n https://src.fedoraproject.org/rpms/rubygem-pg.git /var/lib/mock/f45-build-35157-693/root/chroot_tmpdir/scmroot/rubygem-pg
Cloning into '/var/lib/mock/f45-build-35157-693/root/chroot_tmpdir/scmroot/rubygem-pg'...
$ git fetch origin 3df8b8d5bc47a05fe0b539c4fae0e1e22bede470:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-pg
 * [new ref]         3df8b8d5bc47a05fe0b539c4fae0e1e22bede470 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3df8b8d Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild