import-checker: add a way to directly import certain symbols We'll use this for the 'demandimport' symbol in an upcoming patch.

check-code: allow skipping hasattr check in py3-only code hasattr is safe in Python 3, and in an upcoming patch we can't use util.safehasattr.

profiling: allow loading profiling extension before everything else 6d642ecf1a89 makes profiler start early without loading extensions. That makes it impossible for an extension to add customized profilers. This patch adds a special case: if a profiler is not found but an extension with the same name could be loaded, load that extension first, and expect it to have a "profile" contextmanager method. This allows customized profilers and extension setup time is still profiled.

extensions: allow loading a whitelisted subset of extensions This feature will be used by the next patch.

match: catch attempts to create case-insenstive exact matchers Exact matchers are only created internally (as opposed to from user input) based on a set of files that the caller collected before, so they should always match the list exactly (i.e. case-sensitively).

test: remove aliases forcing date, use default-date Now that we have the default-date by default and all code have been updated, remove the old commands alias that forced the date as they are not longer useful. Writing tests now should be easier for everyone now that all dates should be stable.