tests/sitecustomize.py

pull: list bookmarks before pulling changesets (issue3873)

Consider a bookmark B that exists both locally and remotely. If B is updated
remotely, and then a pull is performed where the pull set contains the new
location of B, the bookmark is updated locally. However, if remote B is
updated in the middle of a pull to a location not in the pull set, the
bookmark won't be updated locally at all.

To fix this, list bookmarks before pulling in changesets, not after. This
still leaves a race open if B gets moved in between listing bookmarks and
pulling in changesets, but the race window is much smaller. Fixing the race
properly would require a bundle format upgrade.

test-hook.t's output changes because we no longer do two listkeys calls during
pull, just one.

test-pull-http.t's output changes because we now search for bookmarks before
searching for changes.

try:
    import coverage
    getattr(coverage, 'process_startup', lambda: None)()
except ImportError:
    pass