format-json: change the invocation, we now edit files in-place

format-json

 #!/usr/bin/env python
 r"""Command-line tool to format software release JSON for slapos.
 
-Inspired by json.tool from python
+Inspired by json.tool from python, but enforcing 2 spaces and non-sorted keys.
+The files are modified in-place.
 
 Usage::
 
-    format-json infile outfile
+    format-json file1.json [file2.json]
 
 """
 
@@ -16,19 +17,16 @@ import collections
 
 
 def main():
-  if len(sys.argv) != 3:
-    raise SystemExit(sys.argv[0] + " infile outfile")
-
-  with open(sys.argv[1], 'rb') as infile:
+  for f in sys.argv[1:]:
+    with open(f, 'rb') as infile:
       try:
         obj = json.load(infile, object_pairs_hook=collections.OrderedDict)
-    except ValueError, e:
+      except ValueError as e:
         raise SystemExit(e)
 
-  with open(sys.argv[2], 'wb') as outfile:
+    with open(f, 'wb') as outfile:
       json.dump(obj, outfile, sort_keys=False, indent=2, separators=(',', ': '))
       outfile.write('\n')
 
-
 if __name__ == '__main__':
   main()