Merge branch 'jc/maint-rev-list-topo-doc'

It was unclear what "--topo-order" was really about in the
documentation. It is not just about "children before parent", but
also about "don't mix lineages".

* jc/maint-rev-list-topo-doc:
rev-list docs: clarify --topo-order description

diff --cc Documentation/rev-list-options.txt
Simple merge