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