$ git clone -n https://src.fedoraproject.org/rpms/rubygem-pkg-config.git /var/lib/mock/f45-build-35150-693/root/chroot_tmpdir/scmroot/rubygem-pkg-config
Cloning into '/var/lib/mock/f45-build-35150-693/root/chroot_tmpdir/scmroot/rubygem-pkg-config'...
$ git fetch origin 3595f8f967f4d4d5617c71b47dc5cfa29c59b6c7:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-pkg-config
 * [new ref]         3595f8f967f4d4d5617c71b47dc5cfa29c59b6c7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 3595f8f Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild