Add version argument and output

Change-Id: I71c970c338297ada898fe5df887ecb975f7c3b29

doc8/main.py

@@ -49,6 +49,7 @@ from stevedore import extension
 from doc8 import checks
 from doc8 import parser as file_parser
 from doc8 import utils
+from doc8 import version
 
 FILE_PATTERNS = ['.rst', '.txt']
 MAX_LINE_LENGTH = 79
@@ -183,7 +184,12 @@ def main():
                         default=[])
     parser.add_argument("-v", "--verbose", dest="verbose", action='store_true',
                         help="run in verbose mode", default=False)
+    parser.add_argument("--version", dest="version", action='store_true',
+                        help="show the version and exit", default=False)
     args = vars(parser.parse_args())
+    if args.get('version'):
+        print(version.version_string())
+        return 0
     args['ignore'] = merge_sets(args['ignore'])
     cfg = extract_config(args)
     args['ignore'].update(cfg.pop("ignore", set()))

doc8/version.py

@@ -0,0 +1,24 @@
+# -*- coding: utf-8 -*-
+
+#    Copyright (C) 2014 Yahoo! Inc. All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+try:
+    from pbr import version as pbr_version
+    _version_info = pbr_version.VersionInfo('doc8')
+    version_string = _version_info.version_string
+except ImportError:
+    import pkg_resources
+    _version_info = pkg_resources.get_distribution('doc8')
+    version_string = lambda: _version_info.version