$ git clone -n https://src.fedoraproject.org/rpms/gcc.git /var/lib/mock/f42-build-861760-170342/root/chroot_tmpdir/scmroot/gcc
Cloning into '/var/lib/mock/f42-build-861760-170342/root/chroot_tmpdir/scmroot/gcc'...
$ git fetch origin 02c34dfa3627ef05d676d30e152a66e77b58529b:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gcc
 * [new ref]         02c34dfa3627ef05d676d30e152a66e77b58529b -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 02c34df 14.2.1-6