$ git clone -n https://src.fedoraproject.org/rpms/cxxtools.git /var/lib/mock/f42-build-3528287-46309/root/chroot_tmpdir/scmroot/cxxtools
Cloning into '/var/lib/mock/f42-build-3528287-46309/root/chroot_tmpdir/scmroot/cxxtools'...
$ git fetch origin e4af85b86ce861f0e58a85a9c1cc9ce279f3f352:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/cxxtools
 * [new ref]         e4af85b86ce861f0e58a85a9c1cc9ce279f3f352 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at e4af85b reenable test suite and fix assertion with _GLIBCXX_ASSERTIONS