Add --release option.

Now that PBR is integrated, we can get more specific version information
that includes the full release string, as pulled from 'git describe':

${latest-tag}.${num_of_commits_since_tag}.${git_short_sha}

Change-Id: I81c466b429c88f6e32b6968b34f8ccf255ba6c50

libra/common/options.py

@@ -18,7 +18,7 @@ import os.path
 import sys
 import ConfigParser
 
-from libra import __version__
+from libra import __version__, __release__
 from logging_handler import CompressedTimedRotatingFileHandler
 
 """
@@ -114,6 +114,10 @@ class Options(object):
             '--version', dest='version', action='store_true',
             help='print version and exit'
         )
+        self.parser.add_argument(
+            '--release', dest='release', action='store_true',
+            help='print full release version info and exit'
+        )
         self.parser.add_argument(
             '-n', '--nodaemon', dest='nodaemon', action='store_true',
             help='do not run in daemon mode'
@@ -159,6 +163,9 @@ class Options(object):
         if args.version:
             print("Libra toolset version %s" % __version__)
             sys.exit(0)
+        if args.release:
+            print("Libra toolset release %s" % __release__)
+            sys.exit(0)
         return args