$ git clone -n https://src.fedoraproject.org/rpms/rust-tempdir.git /var/lib/mock/f42-build-side-1-3584375-46893/root/chroot_tmpdir/scmroot/rust-tempdir
Cloning into '/var/lib/mock/f42-build-side-1-3584375-46893/root/chroot_tmpdir/scmroot/rust-tempdir'...
$ git fetch origin 8505f1e9affe769847ac1a618d785cc8be7bc9d7:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-tempdir
 * [new ref]         8505f1e9affe769847ac1a618d785cc8be7bc9d7 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 8505f1e no longer needed