Merge #11862: Network specific conf sections

c25321f Add config changes to release notes (Anthony Towns)
5e3cbe0 [tests] Unit tests for -testnet/-regtest in [test]/[regtest] sections (Anthony Towns)
005ad26 ArgsManager: special handling for -regtest and -testnet (Anthony Towns)
608415d [tests] Unit tests for network-specific config entries (Anthony Towns)
68797e2 ArgsManager: Warn when ignoring network-specific config setting (Anthony Towns)
d1fc4d9 ArgsManager: limit some options to only apply on mainnet when in default section (Anthony Towns)
8a9817d [tests] Use regtest section in functional tests configs (Anthony Towns)
30f9407 [tests] Unit tests for config file sections (Anthony Towns)
95eb66d ArgsManager: support config file sections (Anthony Towns)
4d34fcc ArgsManager: drop m_negated_args (Anthony Towns)
3673ca3 ArgsManager: keep command line and config file arguments separate (Anthony Towns)

Pull request description:

  The weekly meeting on [2017-12-07](http://www.erisian.com.au/meetbot/bitcoin-core-dev/2017/bitcoin-core-dev.2017-12-07-19.00.log.html) discussed allowing options to bitcoin to have some sensitivity to what network is in use. @theuni suggested having sections in the config file:

      <cfields> an alternative to that would be sections in a config file. and on the
                cmdline they'd look like namespaces. so, [testnet] port=5. or -testnet::port=5.

  This approach is (more or less) supported by `boost::program_options::detail::config_file_iterator` -- when it sees a `[testnet]` section with `port=5`, it will treat that the same as "testnet.port=5". So `[testnet] port=5` (or `testnet.port=5` without the section header) in bitcoin.conf and `-testnet.port=5` on the command line.

  The other aspect to this question is possibly limiting some options so that there is no possibility of accidental cross-contamination across networks. For example, if you're using a particular wallet.dat on mainnet, you may not want to accidentally use the same wallet on testnet and risk reusing keys.

  I've set this up so that the `-addnode` and `-wallet` options are `NETWORK_ONLY`, so that if you have a bitcoin.conf:

      wallet=/secret/wallet.dat
      upnp=1

  and you run `bitcoind -testnet` or `bitcoind -regtest`, then the `wallet=` setting will be ignored, and should behave as if your bitcoin.conf had specified:

      upnp=1

      [main]
      wallet=/secret/wallet.dat

  For any `NETWORK_ONLY` options, if you're using `-testnet` or `-regtest`, you'll have to add the prefix to any command line options. This was necessary for `multiwallet.py` for instance.

  I've left the "default" options as taking precedence over network specific ones, which might be backwards. So if you have:

      maxmempool=200
      [regtest]
      maxmempool=100

  your maxmempool will still be 200 on regtest. The advantage of doing it this way is that if you have `[regtest] maxmempool=100` in bitcoin.conf, and then say `bitcoind -regtest -maxmempool=200`, the same result is probably in line with what you expect...

  The other thing to note is that I'm using the chain names from `chainparamsbase.cpp` / `ChainNameFromCommandLine`, so the sections are `[main]`, `[test]` and `[regtest]`; not `[mainnet]` or `[testnet]` as might be expected.

  Thoughts? Ping @meshcollider @laanwj @jonasschnelli @morcos

Tree-SHA512: f00b5eb75f006189987e5c15e154a42b66ee251777768c1e185d764279070fcb7c41947d8794092b912a03d985843c82e5189871416995436a6260520fb7a4db

Author: laanwj

doc/release-notes-pr12823.md

@@ -0,0 +1,20 @@
+Configuration sections for testnet and regtest
+----------------------------------------------
+
+It is now possible for a single configuration file to set different
+options for different networks. This is done by using sections or by
+prefixing the option with the network, such as:
+
+    main.uacomment=bitcoin
+    test.uacomment=bitcoin-testnet
+    regtest.uacomment=regtest
+    [main]
+    mempoolsize=300
+    [test]
+    mempoolsize=100
+    [regtest]
+    mempoolsize=20
+
+The `addnode=`, `connect=`, `port=`, `bind=`, `rpcport=`, `rpcbind=`
+and `wallet=` options will only apply to mainnet when specified in the
+configuration file, unless a network is specified.

src/chainparamsbase.cpp

@@ -47,4 +47,5 @@ std::unique_ptr<CBaseChainParams> CreateBaseChainParams(const std::string& chain
 void SelectBaseParams(const std::string& chain)
 {
     globalChainBaseParams = CreateBaseChainParams(chain);
+    gArgs.SelectConfigNetwork(chain);
 }

src/init.cpp

@@ -803,6 +803,11 @@ void InitParameterInteraction()
         if (gArgs.SoftSetBoolArg("-whitelistrelay", true))
             LogPrintf("%s: parameter interaction: -whitelistforcerelay=1 -> setting -whitelistrelay=1\n", __func__);
     }
+
+    // Warn if network-specific options (-addnode, -connect, etc) are
+    // specified in default section of config file, but not overridden
+    // on the command line or in this network's section of the config file.
+    gArgs.WarnForSectionOnlyArgs();
 }
 
 static std::string ResolveErrMsg(const char * const optname, const std::string& strBind)