import-checker: rotatecycle is actually the canonical cycle key So refactor to drop cyclekey().

import-checker: make search algorithm non-recursive breadth-first Breadth-first allows finding the shortest cycle including the starting module. This lets us terminate our search early when we've discovered shorter paths already. This gives a tremendous speed-up to the cycle-finding portion of the test, dropping total runtime from 39s to 3s.

import-checker: drop set() from cyclekey()

import-checker: drop duplicate element from cycle This will allow optimizing cyclekey creation

import-checker: fix rotatecycle It was duplicating the last element sometimes.

dirs.addpath: rework algorithm to search forward This improves performance because it uses strchr rather than a loop. For LLVM/clang version "Apple LLVM version 6.0 (clang-600.0.56) (based on LLVM 3.5svn)" on OS X, for a repo with over 200,000 files, this improves perfdirs from 0.248 seconds to 0.230 (7.3%) For gcc 4.4.6 on Linux, for a test repo with over 500,000 files, this improves perfdirs from 0.704 seconds to 0.658 (6.5%).

changeset_printer: use changectx to get status tuple log.parents() can't handle wdir() revision. Because repo.status() creates ctx objects, there would be no benefit to get parent node from changelog.

changeset_printer: replace _meaningful_parentrevs() by changeset_templater's Because changeset_printer needs pctx object anyway, there would be no benefit to avoid creation of pctx in _meaningful_parentrevs().