$ git clone -n https://src.fedoraproject.org/rpms/rust-capnp.git /var/lib/mock/f39-build-2204457-51962/root/chroot_tmpdir/scmroot/rust-capnp
Cloning into '/var/lib/mock/f39-build-2204457-51962/root/chroot_tmpdir/scmroot/rust-capnp'...
$ git fetch origin 64ac9060b319b648ff1b926a2e8089624b92480c:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-capnp
 * [new ref]         64ac9060b319b648ff1b926a2e8089624b92480c -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 64ac906 Update to version 0.18.11; Fixes RHBZ#2257083