$ git clone -n https://src.fedoraproject.org/rpms/perl-Math-BigInt-GMP.git /var/lib/mock/f42-build-side-1-3503245-45980/root/chroot_tmpdir/scmroot/perl-Math-BigInt-GMP
Cloning into '/var/lib/mock/f42-build-side-1-3503245-45980/root/chroot_tmpdir/scmroot/perl-Math-BigInt-GMP'...
$ git fetch origin b2bd25a80756ad16036a2ea2a79718ec3cdf6a3b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/perl-Math-BigInt-GMP
 * [new ref]         b2bd25a80756ad16036a2ea2a79718ec3cdf6a3b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at b2bd25a 1.7002 bump (rhbz#2349245)