tests: stabilize test-merge-tools.t on Windows More fun with `hg import --bypass` to work around Windows limitations. The diffs were generated on Linux, and had a tab to terminate the `+++b/...` lines. But check-code complained about trailing whitespace, and it seems to run without them.

dagutil: remove module The previous commit removed the last consumer of this module. .. api:: dagutil module has been removed Some functionality has been moved to the dagop module. Other functionality can be accomplished via revsets. Differential Revision: https://phab.mercurial-scm.org/D4330

dagop: port revlogdag.linearize() to standalone function The code should functionally be identical. We also port the one consumer in changegroup to use the new standalone function. After this commit, dagutil is no longer used! Differential Revision: https://phab.mercurial-scm.org/D4329

dagutil: use revlog.parentrevs() for resolving parent revisions And remove parents() since it is no longer used. revlog.parentrevs() is almost the same as parents(). The main difference is that parentrevs() can return nullrev. dagop.headrevs() already handles nullrev. We add an inline check for nullrev in the other call site to account for the difference. .. api:: parents() removed from dagutil classes Use parentrevs() on the storage object instead. Differential Revision: https://phab.mercurial-scm.org/D4328

dagop: extract headsetofconnecteds() from dagutil The functionality for resolving the set of DAG heads from a subset simply requires a function to resolve parent revisions. Let's establish a function in the dagop module to do this, which seems to be where generic DAG functionality goes these days. Differential Revision: https://phab.mercurial-scm.org/D4327

setdiscovery: precompute children revisions to avoid quadratic lookup Moving away from dagutil a few commits ago introduced quadratic behavior when resolving children revisions during discovery. This commit introduces a precompute step of the children revisions to avoid the bad behavior. I believe the new code should have near identical performance to what dagutil was doing before. Behavior is still slightly different because we take into account filtered revisions. But this change was made when we moved off dagutil. I added a comment about multiple invocations of this function redundantly calculating the children revisions. I believe this potentially undesirable behavior was present when we used dagutil, as the call to inverse() previously in this function created a new object and required computing children on every invocation. I thought we should document the potential for a performance issue rather than let it go undocumented. Differential Revision: https://phab.mercurial-scm.org/D4326