subrepo: cleanup of subrepo filematcher logic Previously in the worst case we iterated the files in matcher twice and had a method only for this, which reimplemented logic in subdirmatchers constructor. So we replaced the method with a subdirmatcher.files() call.

pycompat: delay loading modules registered to stub Replacement _pycompatstub designed to be compatible with our demandimporter. try-except is replaced by version comparison because ImportError will no longer be raised immediately.

py3: import builtin wrappers automagically by code transformer This should be less invasive than mucking builtins. Since tokenize.untokenize() looks start/end positions of tokens, we calculates them from the NEWLINE token of the future import.