$ git clone -n https://src.fedoraproject.org/rpms/gcc.git /var/lib/mock/f42-build-side-1-3522603-46185/root/chroot_tmpdir/scmroot/gcc
Cloning into '/var/lib/mock/f42-build-side-1-3522603-46185/root/chroot_tmpdir/scmroot/gcc'...
$ git fetch origin 09b578c3e50a419c723566c4ad27a23783364406:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/gcc
 * [new ref]         09b578c3e50a419c723566c4ad27a23783364406 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 09b578c 15.1.1-1