hghave: add check for virtualenv

setup: introduce dummy copies of setuptools flags Since we're filtering out some egg gunk, we need to emulate these flags which disable eggs so that pip still works.

extensions: catch uisetup and extsetup failures and don't let them break hg Otherwise users of the patience diff extension will be unable to run anything at all in hg 4.3 until they figure out what's broken.

tests: add test demonstrating how broken third-party extensions can get I intend to fix this, but will do the fix as a separate change to make the behavior change obvious. This was inspired by some users having the patience diff extension, which broke when we moved bdiff.so so thoroughly the users can't even run 'hg debuginstall'.

extensions: move wrapfilecache function from fsmonitor It makes more sense to put this in core, so other extensions can trivially get access to it without having to rely on importing fsmonitor.

chmod: create a new file when flags are set on a hardlinked file For performance reasons we have several repositories where the files in the working directory of 1 repo are hardlinks to the files of the other repo When an update in one repo results in a chmod of a such a file, the hardlink has to be deleted and replaced by a regular file to make sure that the change does not happen in the other repo

run-tests: make --restart work with output dir

run-tests: output coverage to output dir There do not appear to be any tests for this, and I've never used either of these options before, but this works.

run-tests: write JSON reports to output dir

run-tests: write test times to output dir