82 % test for different branch cache features

    83 branch cache: no features specified

    84 foo                            4:4909a3732169c0c20011c4f4b8fdff4e3d89b23f

    85                                3:bf1bc2f45e834c75404d0ddab57d53beab56e2f8

    86 bar                            2:67ec16bde7f1575d523313b9bca000f6a6f12dca

    87 branch cache: unknown features: dummy, foo, bar

    88 foo                            4:4909a3732169c0c20011c4f4b8fdff4e3d89b23f

    89                                3:bf1bc2f45e834c75404d0ddab57d53beab56e2f8

    90 bar                            2:67ec16bde7f1575d523313b9bca000f6a6f12dca

    91 branch cache: missing features: unnamed

    92 foo                            4:4909a3732169c0c20011c4f4b8fdff4e3d89b23f

    93                                3:bf1bc2f45e834c75404d0ddab57d53beab56e2f8

    94 bar                            2:67ec16bde7f1575d523313b9bca000f6a6f12dca

    95 % test old hg reading branch cache with feature list

    96 ValueError raised correctly, good.