$ git clone -n https://src.fedoraproject.org/rpms/rubygem-mocha.git /var/lib/mock/f45-build-35049-693/root/chroot_tmpdir/scmroot/rubygem-mocha
Cloning into '/var/lib/mock/f45-build-35049-693/root/chroot_tmpdir/scmroot/rubygem-mocha'...
$ git fetch origin 813a78647f228f8544204f652285bb12c8510a8b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-mocha
 * [new ref]         813a78647f228f8544204f652285bb12c8510a8b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 813a786 Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild