$ git clone -n https://src.fedoraproject.org/forks/music/rpms/rust-gengo.git /var/lib/mock/f43-build-59084563-6570967/root/chroot_tmpdir/scmroot/rust-gengo
Cloning into '/var/lib/mock/f43-build-59084563-6570967/root/chroot_tmpdir/scmroot/rust-gengo'...
$ git fetch origin 776be70202af9c14147c946e7b4db7fc01a8cd5a:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/forks/music/rpms/rust-gengo
 * [new ref]         776be70202af9c14147c946e7b4db7fc01a8cd5a -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 776be70 Update to 0.13.0 (close RHBZ#2361954)