dagutil: remove descendantset() and ancestorset() descendantset() is unused after the previous commit. And ancestorset() was only used by descendantset(), so it can be removed as well. .. api:: descendantset() and ancestorset() removed from dagutil Use a revset instead when operating on the changelog. Or use various functionality in the ancestor or dagop modules. Differential Revision: https://phab.mercurial-scm.org/D4315

setdiscovery: use a revset instead of dagutil.descendantset() This is the only use of descendantset() in the repo. Strictly speaking, the revset behaves slightly differently than dagutil. The reason is that dagutil is using revlog.index for DAG traversal and this data structure isn't aware of visibility / filtering. So it can operate on revisions it shouldn't operate on. But our test coverage of this code is pretty comprehensive and this change causes no tests to fail. So I think we are good. Also, the revset parser failed to parse `%ld:: - %ld::`, hence the use of descendants(). I'm not sure if that is a feature or a bug. Differential Revision: https://phab.mercurial-scm.org/D4314