$ git clone -n https://src.fedoraproject.org/rpms/jemalloc.git /var/lib/mock/f42-build-3436880-45433/root/chroot_tmpdir/scmroot/jemalloc
Cloning into '/var/lib/mock/f42-build-3436880-45433/root/chroot_tmpdir/scmroot/jemalloc'...
$ git fetch origin fe882ace3255223156cf4b5e8d2c1e151e9ed3f2:KOJI_FETCH_HEAD
From https://src.fedoraproject.org/rpms/jemalloc
 * [new ref]         fe882ace3255223156cf4b5e8d2c1e151e9ed3f2 -> KOJI_FETCH_HEAD
$ git reset --hard KOJI_FETCH_HEAD
HEAD is now at fe882ac Added build fix from upstream for new gcc