$ git clone -n https://src.fedoraproject.org/rpms/rubygem-process_executer.git /var/lib/mock/f45-build-35162-693/root/chroot_tmpdir/scmroot/rubygem-process_executer
Cloning into '/var/lib/mock/f45-build-35162-693/root/chroot_tmpdir/scmroot/rubygem-process_executer'...
$ git fetch origin 15b1400b7f813e15718ec56fa00b7449bb6f7225:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-process_executer
 * [new ref]         15b1400b7f813e15718ec56fa00b7449bb6f7225 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 15b1400 Update to 4.2.0 rhbz#2526075