Core release note say:
The `prioritisetransaction` RPC no longer takes a `priority_delta` argument, which is replaced by a `dummy` argument for backwards compatibility with clients using positional arguments. The RPC is still used to change the apparent fee-rate of the transaction by using the `fee_delta` argument.
I think we should probably keep the dummy around for a while, and add a deprecated flag to handle the transition.
Yeah fair enough, I was half-expecting this review. Actually the original PR 9602 did fully remove the argument, and I had no idea they restored the parameter as a dummy argument. I just invented the intermediate dummy step myself (the parent Diff) since it was a no-brainer.
The parameter was actually restored in https://github.com/bitcoin/bitcoin/pull/10252/files -- should we replicate its functionality in that "Not supported, so must be zero or null." ?