message: doc: add note on precedence of options in bitcoin.conf
diff: @@ -30,6 +30,21 @@ Network specific options can be:
  - placed into sections with headers `[main]` (not `[mainnet]`), `[test]` (not `[testnet]`) or `[regtest]`;
  - prefixed with a chain name; e.g., `regtest.maxmempool=100`.
  +Network specific options take precedence over non-network specific options.
  +If multiple values for the same option are found with the same precedence, the
  +first one is generally chosen.
  +
  +This means that given the following configuration, `regtest.rpcport` is set to `3000`:
  +
  +```
  +regtest=1
  +rpcport=2000
  +regtest.rpcport=3000
  +
  +[regtest]
  +rpcport=4000
  +```
  +
  ## Configuration File Path
  The configuration file is not automatically created; you can create it using your favorite text editor. By default, the configuration file name is `bitcoin.conf` and it is located in the Bitcoin data directory, but both the Bitcoin data directory and the configuration file path may be changed using the `-datadir` and `-conf` command-line options.
  