MsgFilter should be configurable at run-time

[kdudka]

As pointed out in #8, it would help if MsgFilter could be configured at run-time using some JSON input file. Also the currently defined filters should be available somewhere in the same JSON format, so that csdiff users do not have to speak C++.

[praiskup]

I tested this, but it doesn't appear to be working. What am I doing wrong?

$ cat /tmp/filter 
{
    "msg-filter" : [
        {
             "checker" : "PYLINT_WARNING",
             "regexp" : "Too",
             "replace" : "Boo"
        }
    ]
}
$ cat /tmp/copr-linter-xsu3rrtk/old
{
  "defects": [
    {
      "checker": "PYLINT_WARNING",
      "events": [
        {
          "file_name": "copr_backend/sign.py",
          "line": 157,
          "column": 8,
          "event": "W0707[raise-missing-from]",
          "message": "create_user_keys: Consider explicitly re-raising using the 'from' keyword"
        }
      ]
    },
    {
      "checker": "PYLINT_WARNING",
      "events": [
        {
          "file_name": "copr_backend/sign.py",
          "line": 177,
          "column": 16,
          "event": "E1305[too-many-format-args]",
          "message": "_unsign_one: Too many arguments for format string"
        }
      ]
    }
  ]
}
$ cat /tmp/copr-linter-xsu3rrtk/new
{
  "defects": [
    {
      "checker": "PYLINT_WARNING",
      "events": [
        {
          "file_name": "copr_backend/sign.py",
          "line": 159,
          "column": 8,
          "event": "W0707[raise-missing-from]",
          "message": "create_user_keys: Consider explicitly re-raising using the 'from' keyword"
        }
      ]
    }
    ]
}
$ csdiff --filter-file /tmp/filter -c -x /tmp/copr-linter-xsu3rrtk/old /tmp/copr-linter-xsu3rrtk/new
Error: PYLINT_WARNING:
copr_backend/sign.py:177:16: E1305[too-many-format-args]: _unsign_one: Too many arguments for format string

[praiskup]

I was wrong, the event format on csdiff's stdout isn't affected by the filter (just the internal comparison). Sorry for the confusion above.