$ git clone -n https://src.fedoraproject.org/rpms/perl-Archive-Tar.git /var/lib/mock/f42-build-side-1-3499451-45965/root/chroot_tmpdir/scmroot/perl-Archive-Tar
Cloning into '/var/lib/mock/f42-build-side-1-3499451-45965/root/chroot_tmpdir/scmroot/perl-Archive-Tar'...
$ git fetch origin da6ef71ef8ddea50af7edd9732aa348e7e59a750:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/perl-Archive-Tar
 * [new ref]         da6ef71ef8ddea50af7edd9732aa348e7e59a750 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at da6ef71 3.04 bump (rhbz#2347586)