$ git clone -n https://src.fedoraproject.org/rpms/rust-ref-cast-impl.git /var/lib/mock/f39-build-1495451-34544/root/chroot_tmpdir/scmroot/rust-ref-cast-impl
Cloning into '/var/lib/mock/f39-build-1495451-34544/root/chroot_tmpdir/scmroot/rust-ref-cast-impl'...
$ git fetch origin 5f7a6f3ad4b3642bcb49cc1c4b4083071d590ec0:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-ref-cast-impl
 * [new ref]         5f7a6f3ad4b3642bcb49cc1c4b4083071d590ec0 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 5f7a6f3 Update to version 1.0.20; Fixes RHBZ#2232468