Bug 729778: check for unknown commands before reading package.json. r=@…

…MarkH

This allows mistyped commands like "cfx blah" to emit the useful (and
originally intended) "Unknown command, try --help" message. Some very old
refactoring (before release 0.1) caused the code that reads package.json to
be run too early, such that "cfx blah" emits "unable to find package.json"
instead of "Unknown command".

python-lib/cuddlefish/__init__.py

@@ -532,6 +532,10 @@ def run(arguments=sys.argv[1:], target_cfg=None, pkg_cfg=None,
         filename = generate.generate_static_docs(env_root)
         print >>stdout, "Wrote %s." % filename
         return
+    elif command not in ["xpi", "test", "run"]:
+        print >>sys.stderr, "Unknown command: %s" % command
+        print >>sys.stderr, "Try using '--help' for assistance."
+        sys.exit(1)
 
     target_cfg_json = None
     if not target_cfg:
@@ -569,9 +573,7 @@ def run(arguments=sys.argv[1:], target_cfg=None, pkg_cfg=None,
     elif command == "run":
         use_main = True
     else:
-        print >>sys.stderr, "Unknown command: %s" % command
-        print >>sys.stderr, "Try using '--help' for assistance."
-        sys.exit(1)
+        assert 0, "shouldn't get here"
 
     if use_main and 'main' not in target_cfg:
         # If the user supplies a template dir, then the main