$ git clone -n https://src.fedoraproject.org/rpms/rust-varbincode.git /var/lib/mock/f41-build-side-1-3099412-39334/root/chroot_tmpdir/scmroot/rust-varbincode
Cloning into '/var/lib/mock/f41-build-side-1-3099412-39334/root/chroot_tmpdir/scmroot/rust-varbincode'...
$ git fetch origin c46a9f7503e63f4310c5367a1d358e7751cb58ae:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-varbincode
 * [new ref]         c46a9f7503e63f4310c5367a1d358e7751cb58ae -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at c46a9f7 no longer needed