Use real revision mapping in bot_update module

scripts/slave/bot_update.py

Index: scripts/slave/bot_update.py
diff --git a/scripts/slave/bot_update.py b/scripts/slave/bot_update.py
index 1df92f1b25a03ee57db1711f48a6da22a00cab65..b25b6a8702976dd23dfedeba5bd36b4a833e1e87 100755
--- a/scripts/slave/bot_update.py
+++ b/scripts/slave/bot_update.py
@@ -1038,8 +1038,13 @@ def parse_args():
   parse.add_option('-f', '--force', action='store_true',
                    help='Bypass check to see if we want to be run. '
                         'Should ONLY be used locally.')
-  parse.add_option('--revision_mapping')
-  parse.add_option('--revision-mapping')  # Backwards compatability.
+  parse.add_option('--revision_mapping',
+                   help='{"path/to/repo/": "property_name"}')
+  parse.add_option('--revision_mapping_file',
+                   help=('Same as revision_mapping, except its a path to a json'
+                         ' file containing that format.'))
+  parse.add_option('--revision-mapping', # Backwards compatability.
+                   help='DEPRECATED, use "revision_mapping" instead')
   # TODO(hinoka): Support root@revision format.
   parse.add_option('--revision',
                    help='Revision to check out. Can be an SVN revision number, '
@@ -1062,7 +1067,16 @@ def parse_args():
                    help='Output JSON information into a specified file')
 
 
-  return parse.parse_args()
+  options, args = parse.parse_args()
+
+  if options.revision_mapping_file is not None:
+    if options.revision_mapping is not None:
+      print ('WARNING: revision_mapping_file was set at the same '
+             'time as revision_mapping?')
+    with open(options.revision_mapping_file, 'r') as f:
+      options.revision_mapping = json.load(f)
+
+  return options, args
 
 
 def main():