graphlog: fix --follow-first --rev combinations This solves a similar problem than the previous --follow/--rev patch. This time we need changelog.ancestors()/descendants() filtering on first parent. Duplicating the code looked better than introducing keyword arguments. Besides, the ancestors() version was already implemented in follow() revset.

graphlog: fix --follow --rev combinations The previous behaviour of --follow was really a subset of what is really happening in log command: - If --rev is not passed, default to '.:0' - Resolve --rev into a revision list "revs" - Set the starting revision to revs[0] - If revs[1] > revs[0] keep descendants(revs[0]) in revs, otherwise keep ancestors.