$ git clone -n https://src.fedoraproject.org/rpms/rust-prost-build.git /var/lib/mock/f42-build-side-1-3539981-46572/root/chroot_tmpdir/scmroot/rust-prost-build
Cloning into '/var/lib/mock/f42-build-side-1-3539981-46572/root/chroot_tmpdir/scmroot/rust-prost-build'...
$ git fetch origin fe399b433a09ef7cbe37a979f8ae7bdc1cc94585:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-prost-build
 * [new ref]         fe399b433a09ef7cbe37a979f8ae7bdc1cc94585 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fe399b4 Allow petgraph 0.8