Merge #14708: Warn unrecognised sections in the config file

3fb09b9889 Warn unrecognized sections in the config file (Akio Nakamura)

Pull request description:

  This PR intends to resolve #14702.

  In the config file, sections are specified by square bracket pair "[]"$,
  or included in the option name itself which separated by a period"(.)".

  Typicaly, [testnet] is not a correct section name and specified options
  in that section are ignored but user cannot recognize what is happen.

  So, add some log-warning messages if unrecognized section names are
  present in the config file after checking section only args.

  note: Currentry, followings are out of scope of this PR.
  1) Empty section name or option name can describe.
  e.g. [] , .a=b, =c
  2) Multiple period characters can exist in the section name and option name.
  e.g. [c.d.e], [..], f.g.h.i=j, ..=k

Tree-SHA512: 2cea02a0525feb40320613989a75cd7b7b1bd12158d5e6f3174ca77e6a25bb84425dd8812f62483df9fc482045c7b5402d69bc714430518b1847d055a2dc304b

test/functional/feature_config_args.py

@@ -33,6 +33,11 @@ class ConfArgsTest(BitcoinTestFramework):
             conf.write('server=1\nrpcuser=someuser\nrpcpassword=some#pass')
         self.nodes[0].assert_start_raises_init_error(expected_msg='Error reading configuration file: parse error on line 3, using # in rpcpassword can be ambiguous and should be avoided')
 
+        with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
+            conf.write('testnot.datadir=1\n[testnet]\n')
+        self.restart_node(0)
+        self.nodes[0].stop_node(expected_stderr='Warning: Section [testnet] is not recognized.' + os.linesep + 'Warning: Section [testnot] is not recognized.')
+
         with open(inc_conf_file_path, 'w', encoding='utf-8') as conf:
             conf.write('')  # clear