$ git clone -n https://src.fedoraproject.org/rpms/rust-serde_buf.git /var/lib/mock/f41-build-side-1-3134917-39764/root/chroot_tmpdir/scmroot/rust-serde_buf
Cloning into '/var/lib/mock/f41-build-side-1-3134917-39764/root/chroot_tmpdir/scmroot/rust-serde_buf'...
$ git fetch origin a77551f8f2a4b29539bcd9f9c13115f5ae111e2e:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-serde_buf
 * [new ref]         a77551f8f2a4b29539bcd9f9c13115f5ae111e2e -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at a77551f no longer needed