Darcs now shows the internal hash for each patch in a format like:
patch f4128969c4700a0b34414390d04159cb6b11b4e5
Author: bob <bob>
Date: Sun May 21 22:44:55 NZST 2017
* patch name
- further details
Adding the regex "\\|^patch \\(?1:[.0-9a-f]+\\)" to log-view-message-re seems to be sufficient to use the hash.
cheers
Rohan