$ git clone -n https://src.fedoraproject.org/rpms/gcc.git /var/lib/mock/f42-build-868501-176138/root/chroot_tmpdir/scmroot/gcc
Cloning into '/var/lib/mock/f42-build-868501-176138/root/chroot_tmpdir/scmroot/gcc'...
$ git fetch origin f97b22af1011d1a9629418ccb1bed9f6a5196855:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gcc
 * [new ref]         f97b22af1011d1a9629418ccb1bed9f6a5196855 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at f97b22a 15.0.1-0.4