scmutil.filecacheentry: make stat argument to constructor mandatory There's no real upside to making stat optional -- this constructor has just two callers.

test-filecache.py: add markers to the output for each event Previously it was possible that a different, incorrect set of events might print out 'creating' the same number of times.

test-filecache.py: make setbeforeget test clearer '0' and 'None' as outputs tripped me up. Make the distinction between values set externally and values computed by calling the decorated function clearer.

test-module-imports.t: new test to use the import cycle detector

import-checker: try a little harder to show fewer cycles This makes sure that all cycles begin with the lexicographically first module, so that we're less likely to show overlapping cycles in the final analysis.

import-checker: ignore nested imports

contrib: add an import checker This checks for cycles in the module graph and verifies that imports of stdlib modules are not on the same line as relative imports of mercurial modules.

makememctx: move from patch to context to break import cycle

cleanup: move stdlib imports to their own import statement There are a few warnings still produced by my import checker, but those are false positives produced by modules that share a name with stdlib modules.

pathutil: tease out a new library to break an import cycle from canonpath use