option to print only the version of a package

Example:
    $ pbr info -s pkgname
    1.2.3

Change-Id: Ic66848dbe44ed946800979fb73776ab6d00869f6
Signed-off-by: Gaetan Semet <gaetan@xeberon.net>

pbr/cmd/main.py

@@ -40,8 +40,11 @@ def get_sha(args):
 
 
 def get_info(args):
-    print("{name}\t{version}\t{released}\t{sha}".format(
-        **_get_info(args.name)))
+    if args.short:
+        print("{version}".format(**_get_info(args.name)))
+    else:
+        print("{name}\t{version}\t{released}\t{sha}".format(
+            **_get_info(args.name)))
 
 
 def _get_info(name):
@@ -98,6 +101,8 @@ def main():
         'info', help='print version info for package')
     cmd_info.set_defaults(func=get_info)
     cmd_info.add_argument('name', help='package to print info of')
+    cmd_info.add_argument('-s', '--short', action="store_true",
+                          help='only display package version')
 
     cmd_freeze = subparsers.add_parser(
         'freeze', help='print version info for all installed packages')

releasenotes/notes/cmd-e6664dcbd42d3935.yaml

@@ -0,0 +1,11 @@
+---
+features:
+  - |
+    Add an option to print only the version of a package
+
+    Example:
+
+    .. code-block:: bash
+
+        $ pbr info -s pkgname
+        1.2.3