If I want to play about with cross-chain messaging (xcm) what's the best way to get an environment up and running?
One option is polkadot-launch, which will mount parachains for you into the relay chain.
For building the relay chain using the
cargo build --release --fast-runtime (there is a
--profile production rather than
--release but the
lto means that takes a lot longer to compile)
The mounting process that
polka-launch uses assumes that the
sudo pallet is included in the relay chain. At the moment there is no flag to achieve this - you will have to add it into the runtime
The relay-chain and the parachains have embedded the runtime wasm blob in them, but you can provide an alternative in raw JSON format if you want to start from an earlier version of the runtime.