hgweb: ignore filtered revision in revnav This changeset checks that a revision is known before adding it to the navigation. This will prevent traceback on filtered repository. This changeset result in an incorrect behaviors, Navigation link may be dropped without any replacement. However this bad navigation generation is much better than a crash

  $ check_code="$TESTDIR"/../contrib/check-code.py
  $ cd "$TESTDIR"/..
  $ if hg identify -q > /dev/null; then :
  > else
  >     echo "skipped: not a Mercurial working dir" >&2
  >     exit 80
  > fi

New errors are not allowed. Warnings are strongly discouraged.

  $ hg manifest | xargs "$check_code" --warnings --nolineno --per-file=0