ancestor: unroll loop of parents in _lazyancestorsiter() This change itself isn't major performance win, but it helps optimizing the visit loop for contiguous chains. See the next patch.

ancestor: return early from _lazyancestorsiter() when reached to stoprev There's no need to empty the heap.

ancestor: remove alias of initrevs from _lazyancestorsiter() It's just redundant and less comprehensible.

narrow: validate patterns returned by expandnarrow Remotes could supply malicious or invalid patterns. We should validate them as soon as possible. Differential Revision: https://phab.mercurial-scm.org/D4523

narrowspec: limit patterns to path: and rootfilesin: (BC) Some matcher patterns are computationally expensive and may even have security issues (e.g. evaluating some file sets). For these reasons, we want to limit the types of matcher patterns that can be used in narrow specs and by command line arguments used for defining narrow specs. This commit teaches ``narrowspec.parsepatterns()`` to validate the pattern types against "safe" patterns. Surprisingly, no existing tests broke. So tests for the feature have been added. We also added a function to validate a patterns data structure. This will be used in future commits. Differential Revision: https://phab.mercurial-scm.org/D4522

narrow: mark wire proto capability names experimental and versioned We already plan to add a "widen" wire protocol command to the "narrow" capability, so let's version the capabilities as "exp-narrow-1" and "exp-ellipses-1". When we add the "widen" command, we will then add a "exp-narrow-2" capability to indicate support for that command. Differential Revision: https://phab.mercurial-scm.org/D4529