revset: rename revsbetween to reachableroots and add an argument 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. This patch rename 'revsbetween' to 'reachableroots' and makes the computation of the full path optional. This will allow graphlog to compute grandparents using 'reachableroots' and remove the need for a dedicated grandparent function.