$ git clone -n https://src.fedoraproject.org/rpms/rust-custom_error.git /var/lib/mock/f41-build-side-1-2940050-35321/root/chroot_tmpdir/scmroot/rust-custom_error
Cloning into '/var/lib/mock/f41-build-side-1-2940050-35321/root/chroot_tmpdir/scmroot/rust-custom_error'...
$ git fetch origin e5bb752610a32cc3f0efe1c09641933e5d75fe05:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rust-custom_error
 * [new ref]         e5bb752610a32cc3f0efe1c09641933e5d75fe05 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e5bb752 unused leaf package for more than two release cycles