setdiscovery: use revset for resolving DAG heads in a subset This was the final use of dagutil in setdiscovery! For reasons I didn't investigate, feeding a set with nullrev into the heads() revset resulted in a bunch of tests failing. Filtering out nullrev from the input set fixes things. Differential Revision: https://phab.mercurial-scm.org/D4324

dagutil: remove ability to invert instances The previous commit removed the last consumer of this feature. .. api:: remove inverse() methods from classes in dagutil Differential Revision: https://phab.mercurial-scm.org/D4323

setdiscovery: don't use dagutil for parent resolution _updatesample()'s one remaining use of revlogdag is for resolving the parents of a revision. In 2 cases, we actually resolve parents. In 1, we operate on the inverted DAG and resolve children. This commit teaches _updatesample() to receive an argument defining the function to resolve "parent" revisions. Call sites pass in changelog.parentrevs() or a wrapper around changelog.children() accordingly. The use of children() is semantically correct. But it is quadratic, since revlog.children() does a range scan over all revisions starting at its input and effectively calls parentrevs() to build up the list of children. So calling it repeatedly in a loop is a recipe for bad performance. I will be implementing something better in a subsequent commit. I wanted to get the porting off of dagutil done in a way that was simple and correct. Like other patches in this series, this change is potentially impacted but revlogdag's ignorance of filtered revisions. The new code is filtering aware, since changelog's revs() (used by children() will skip filtered revisions and therefore hidden children won't appear. This is potentially backwards incompatible. But no tests fail and I think this code should respect visibility. Differential Revision: https://phab.mercurial-scm.org/D4322

setdiscovery: use revsets for computing a subset's heads and roots revlogdag.headsetofconnecteds() obtains the set of DAG heads in a given set of revs. revlogdag.inverse() inverts the DAG order and makes headsetofconnecteds() obtain the DAG roots in a given subset. Both of these can be expressed with a revset. Like other patches in this series, revlogdag uses revlog.index and thus doesn't take filtering into account. Revsets do. So there is a chance for regressions with this change. But no tests fail. And I think this code should take filtering into account since hidden changesets shouldn't factor into discovery (unless operating on the hidden repository). Differential Revision: https://phab.mercurial-scm.org/D4321

dagutil: remove heads() and localsubset from revlogdag.__init__ The previous commit removed the last consumer of this API. I'm not going to mark as API incompatible because I doubt anybody used this functionality (outside of possibly passing an argument to revlogdag.__init__). I intend to remove revlogdag later in this series and its API annotation will cover this one. Differential Revision: https://phab.mercurial-scm.org/D4320

setdiscovery: pass head revisions into sample functions This eliminates the last remaining consumer of heads() and related functionality in dagutil. Differential Revision: https://phab.mercurial-scm.org/D4319

setdiscovery: pass heads into _updatesample() In preparation for eliminating the use of dagutil. Since _takefullsample() operates on the inverted DAG, it is easier to have the caller pass in the relevant set instead of teaching _updatesample() about when to invert the DAG. We keep the logic identical for now: future commits will remove dagutil. Differential Revision: https://phab.mercurial-scm.org/D4318

setdiscovery: use a revset for finding DAG heads in a subset The march towards moving away from dagutil continues. Like other patches moving us away from dagutil, there is the potential for regressions to occur because revlogdag's headsetofconnecteds() uses revlog.index, which doesn't take filtering into account. The revset layer does. But no tests fail, so we appear to be in the clear. Differential Revision: https://phab.mercurial-scm.org/D4317

setdiscovery: reflect use of revs instead of nodes This code all operates on revision numbers. Update variable names and comments accordingly. Differential Revision: https://phab.mercurial-scm.org/D4316

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

setdiscovery: don't use dagutil to compute heads This is a relatively trivial operation to perform. We don't need to use dagutil. This brings us one step closer to eliminating dagutil. We still need to populate the heads on revlogdag because later functionality relies on it. Differential Revision: https://phab.mercurial-scm.org/D4310