revset: make revsbetween public This patch is part of a series of patches to speed up the computation of revset.revsbetween by introducing a C implementation. The main motivation is to speed up smartlog on big repositories. At the end of the series, on our big repositories the computation of revsbetween is 10-50x faster and smartlog on is 2x-5x faster. Later in this serie, we want to reuse the implementation of revsbetween in the changelog module, therefore, we make it public.