new script to update untranslated messages from other language file

gluon/languages.py

@@ -995,6 +995,23 @@ def update_all_languages(application_path):
             findT(application_path, language[:-3])
 
 
+def update_from_langfile(target, source):
+    """this will update untranslated messages in target from source (where both are language files)
+    this can be used as first step when creating language file for new but very similar language
+        or if you want update your app from welcome app of newer web2py version
+        or in non-standard scenarios when you work on target and from any reason you have partial translation in source
+    """
+    src = read_dict(source)
+    sentences = read_dict(target)
+    for key in sentences:
+        val = sentences[key]
+        if not val or val == key:
+            new_val = src.get(key)
+            if new_val and new_val != val:
+                sentences[key] = new_val
+    write_dict(target, sentences)
+
+
 if __name__ == '__main__':
     import doctest
     doctest.testmod()