cbuildbot.py: add an example --version string

BUG=chromium:307211
TEST=None

Change-Id: I743ced81312b20af13edc84725b9b1bfd210f17d
Reviewed-on: https://chromium-review.googlesource.com/173024
Reviewed-by: Aviv Keshet <akeshet@chromium.org>
Commit-Queue: Aviv Keshet <akeshet@chromium.org>
Tested-by: Aviv Keshet <akeshet@chromium.org>
diff --git a/scripts/cbuildbot.py b/scripts/cbuildbot.py
index e8ecae9..13d5299 100644
--- a/scripts/cbuildbot.py
+++ b/scripts/cbuildbot.py
@@ -1079,7 +1079,8 @@
                                'timeout.')
   group.add_remote_option('--version', dest='force_version', default=None,
                           help='Used with manifest logic.  Forces use of this '
-                               'version rather than create or get latest.')
+                               'version rather than create or get latest. '
+                               'Examples: 4815.0.0-rc1, 4815.1.2')
 
   parser.add_option_group(group)