$ git clone -n https://src.fedoraproject.org/rpms/rust-build-fs-tree.git /var/lib/mock/f40-build-2231342-53270/root/chroot_tmpdir/scmroot/rust-build-fs-tree
Cloning into '/var/lib/mock/f40-build-2231342-53270/root/chroot_tmpdir/scmroot/rust-build-fs-tree'...
$ git fetch origin 65bb49135d680f290d259eb5e6e2d5df3fb744e1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-build-fs-tree
 * [new ref]         65bb49135d680f290d259eb5e6e2d5df3fb744e1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 65bb491 Update to 0.6.0