def _find_combo_match(path):
"""
Calculate the key to check the MEDIASYNC['JOINED'] dict for, perform the
lookup, and return the matching key string if a match is found. If no
match is found, return None instead.
"""
key_str = _form_key_str(path)
if not key_str:
# _form_key_str() says this isn't even a CSS/JS file.
return None
if not JOINED.has_key(key_str):
# No combo file match found. Must be an single file.
return None
else:
# Combo match found, return the JOINED key.
return key_str
