$ git clone -n https://src.fedoraproject.org/rpms/perl-Math-BigInt.git /var/lib/mock/f41-build-815666-149668/root/chroot_tmpdir/scmroot/perl-Math-BigInt
Cloning into '/var/lib/mock/f41-build-815666-149668/root/chroot_tmpdir/scmroot/perl-Math-BigInt'...
$ git fetch origin 31b6cf0531a519039ae74623be2f7de783aa39c6:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/perl-Math-BigInt
 * [new ref]         31b6cf0531a519039ae74623be2f7de783aa39c6 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 31b6cf0 Perl 5.40 rebuild