tests/sitecustomize.py

upgrade: explicitly warn when a `--no-xxx` flag is overwritten

Some format upgrade/downgrades -needs- revlog to be recomputed. So we now
detect that individually and warn when it contradict explicitly passed flag.

This is part of a larger series to make `debugupgraderepo` smarter about which
revlog it picks by default.

Differential Revision: https://phab.mercurial-scm.org/D11869

from __future__ import absolute_import
import os

if os.environ.get('COVERAGE_PROCESS_START'):
    try:
        import coverage
        import uuid

        covpath = os.path.join(
            os.environ['COVERAGE_DIR'], 'cov.%s' % uuid.uuid1()
        )
        cov = coverage.coverage(data_file=covpath, auto_data=True)
        cov._warn_no_data = False
        cov._warn_unimported_source = False
        cov.start()
    except ImportError:
        pass