$ git clone -n https://src.fedoraproject.org/rpms/perl-Crypt-Random-Source.git /var/lib/mock/f40-build-2239058-53593/root/chroot_tmpdir/scmroot/perl-Crypt-Random-Source
Cloning into '/var/lib/mock/f40-build-2239058-53593/root/chroot_tmpdir/scmroot/perl-Crypt-Random-Source'...
$ git fetch origin fd71b5462c701af9b98305deea7a9631fbb38461:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/perl-Crypt-Random-Source
 * [new ref]         fd71b5462c701af9b98305deea7a9631fbb38461 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fd71b54 Improvements to the spec file