$ git clone -n https://src.fedoraproject.org/rpms/perl-Math-BigInt.git /var/lib/mock/f42-build-3159725-40889/root/chroot_tmpdir/scmroot/perl-Math-BigInt
Cloning into '/var/lib/mock/f42-build-3159725-40889/root/chroot_tmpdir/scmroot/perl-Math-BigInt'...
$ git fetch origin aecb31b79a0e0a156f7d19c94c91c7ef112bf46b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/perl-Math-BigInt
 * [new ref]         aecb31b79a0e0a156f7d19c94c91c7ef112bf46b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at aecb31b 2.003004 bump (rhbz#2341776)