$ git clone -n https://src.fedoraproject.org/rpms/rubygem-bootsnap.git /var/lib/mock/f40-build-733938-105578/root/chroot_tmpdir/scmroot/rubygem-bootsnap
Cloning into '/var/lib/mock/f40-build-733938-105578/root/chroot_tmpdir/scmroot/rubygem-bootsnap'...
$ git fetch origin 790b8d4ac8a5f80b6c94e3ed4f9bce468993c933:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/rubygem-bootsnap
 * [new ref]         790b8d4ac8a5f80b6c94e3ed4f9bce468993c933 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at 790b8d4 Fix FTBFS due to compatibility with Minitest 5.19+.