tests/hghave

filelog: raise CensoredNodeError when hash checks fail with censor metadata

With this change, when a revlog revision hash does not match its content, and
the content is empty with a special metadata key, the integrity failure is
assumed to be intentionally caused to remove sensitive content from repository
history.

To allow different Mercurial functionality to handle this scenario differently
a more specific exception is raised than "ordinary" hash failures.

Alternatives to this approach include, but are not limited to:

- Calling a hook when hashes mismatch to allow arbitrary tombstone validation.
  Cons: Irresponsibly easy to disable integrity checking altogether.
- Returning empty revision data eagerly instead of raising, masking the error.
  Cons: Push/pull won't roundtrip the tombstone, so client repos are unusable.
- Doing nothing differently at this layer. Callers must do their own detection
  of tombstoned data if they want to handle some hash checks and not others.
  - Impacts dozens of callsites, many of which don't have the revision data
  - Would probably be missing one or two callsites at any given time
  - Currently we throw a RevlogError, as do 12 other places in revlog.py.
    Callers would need to parse the exception message and/or ensure
    RevlogError is not thrown from any other part of their call tree.

#!/usr/bin/env python
"""Test the running system for features availability. Exit with zero
if all features are there, non-zero otherwise. If a feature name is
prefixed with "no-", the absence of feature is tested.
"""
import optparse
import sys
import hghave

checks = hghave.checks

def list_features():
    for name, feature in checks.iteritems():
        desc = feature[1]
        print name + ':', desc

def test_features():
    failed = 0
    for name, feature in checks.iteritems():
        check, _ = feature
        try:
            check()
        except Exception, e:
            print "feature %s failed:  %s" % (name, e)
            failed += 1
    return failed

parser = optparse.OptionParser("%prog [options] [features]")
parser.add_option("--test-features", action="store_true",
                  help="test available features")
parser.add_option("--list-features", action="store_true",
                  help="list available features")
parser.add_option("-q", "--quiet", action="store_true",
                  help="check features silently")

if __name__ == '__main__':
    options, args = parser.parse_args()
    if options.list_features:
        list_features()
        sys.exit(0)

    if options.test_features:
        sys.exit(test_features())

    quiet = options.quiet

    failures = 0

    def error(msg):
        global failures
        if not quiet:
            sys.stderr.write(msg + '\n')
        failures += 1

    for feature in args:
        negate = feature.startswith('no-')
        if negate:
            feature = feature[3:]

        if feature not in checks:
            error('skipped: unknown feature: ' + feature)
            sys.exit(2)

        check, desc = checks[feature]
        try:
            available = check()
        except Exception, e:
            error('hghave check failed: ' + feature)
            continue

        if not negate and not available:
            error('skipped: missing feature: ' + desc)
        elif negate and available:
            error('skipped: system supports %s' % desc)

    if failures != 0:
        sys.exit(1)