$ git clone -n https://src.fedoraproject.org/rpms/perl-Test-LongString.git /var/lib/mock/f45-build-26731-619/root/chroot_tmpdir/scmroot/perl-Test-LongString
Cloning into '/var/lib/mock/f45-build-26731-619/root/chroot_tmpdir/scmroot/perl-Test-LongString'...
$ git fetch origin 61a6b7e6493e17f0e3e28ff4a9acfe31a4ad9c34:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/perl-Test-LongString
 * [new ref]         61a6b7e6493e17f0e3e28ff4a9acfe31a4ad9c34 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 61a6b7e Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild