$ git clone -n https://src.fedoraproject.org/rpms/rust-derivative.git /var/lib/mock/f38-build-side-43-rust-devel-1411178-31429/root/chroot_tmpdir/scmroot/rust-derivative
Cloning into '/var/lib/mock/f38-build-side-43-rust-devel-1411178-31429/root/chroot_tmpdir/scmroot/rust-derivative'...
$ git fetch origin 04dbc316335054cda4821012e4911ff54fe0fde1:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-derivative
 * [new ref]         04dbc316335054cda4821012e4911ff54fe0fde1 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 04dbc31 Disable test that fails with Rust 1.66+