Merge #751: RPC doc generating script: always connect to regtest

a25cd3b RPC doc generating script: always connect to regtest (Sebastian Falbesoner)

Pull request description:

  See Bitcoin Core PR bitcoin/bitcoin#20987, in particular the discussion bitcoin/bitcoin#20987 (comment).

  The recommended network for generating RPC docs is regtest, as stated in the script's file header comments:
  ```// (2) install bitcoin core, set it up to use regtest```

  To achieve this, the user previosly needed to manually put `regtest=1` into
  `~/.bitcoin/bitcoin.conf` -- the script didn't specify a concrete network, so
  without config file setting, mainnet was used. With the change in this commit,
  we will always connect to regtest by passing the `-regtest` option to the
  `bitcoin-cli` invokation.

  With this change, [harding's well-described way to use the script involving file editing via mighty vi(m)](bitcoin/bitcoin#20987 (comment)) will be reduced to just running the following commands:
  ```
  $ bitcoind -regtest -daemon
  $ go run generate.go
  $ bitcoin-cli -regtest stop
  ```

  Note that I'm far from a golang expert and just tried to wrap my head around variadic functions and slices. Prepending the arguments slice with the chainoption (`-regtest`) seemed the easiest solution to me, but curious to hear how a more "gothonic" (does that word exist?) approach would look like.

ACKs for top commit:
  laanwj:
    Tested ACK a25cd3b

Tree-SHA512: 566aeb6c13e35baef88b0aefe6445fbe90c1d4df1e8310a0a5e910dd947745f00e206705940ed3701bd6c763a425d23ffbbf0ea331dbde3dfe61d75b22ebee3c

Author: laanwj

contrib/doc-gen/generate.go

@@ -20,6 +20,7 @@ import (
 )
 
 const BITCOIN_COMMAND = "bitcoin-cli"
+const BITCOIN_CHAINOPTION = "-regtest"
 
 type Command struct {
 	Name        string
@@ -158,9 +159,10 @@ func open(path string) io.Writer {
 }
 
 func run(args ...string) string {
+	args = append([]string{BITCOIN_CHAINOPTION}, args...)
 	out, err := exec.Command(BITCOIN_COMMAND, args...).CombinedOutput()
 	if err != nil {
-		log.Fatalf("Cannot run bitcoin-cli: %s, is bitcoind running?", err.Error())
+		log.Fatalf("Cannot run bitcoin-cli: %s, is bitcoind (regtest) running?", err.Error())
 	}
 
 	return string(out)