cli: tweak -H output to remove format-hint fields.

-H removes the top-level if there's only one, and 'format-hint'
breaks this heuristic, so we end up with:

```
help=command=autocleaninvoice [cycle_seconds] [expired_by]
category=plugin
description=Set up autoclean of expired invoices.
verbose=Perform cleanup every {cycle_seconds} (default 3600), or disable autoclean if 0. Clean up expired invoices that have expired for {expired_by} seconds (default 86400).
command=check command_to_check
```

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

cli/lightning-cli.c

@@ -375,13 +375,15 @@ static void tal_error(const char *msg)
 	abort();
 }
 
-static enum format delete_format_hint(const char *resp,
-				      jsmntok_t **toks,
-				      jsmntok_t *result)
+static enum format delete_format_hint(const char *resp, jsmntok_t **toks)
 {
+	const jsmntok_t *result = json_get_member(resp, *toks, "result");
 	const jsmntok_t *hint;
 	enum format format = JSON;
 
+	if (!result)
+		return format;
+
 	hint = json_get_member(resp, result, "format-hint");
 	if (!hint)
 		return format;
@@ -390,7 +392,8 @@ static enum format delete_format_hint(const char *resp,
 		format = HUMAN;
 
 	/* Don't let hint appear in the output! */
-	json_tok_remove(toks, result, hint-1, 1);
+        /* Note the aritmetic on *toks for const-washing */
+	json_tok_remove(toks, *toks + (result - *toks), hint-1, 1);
 	return format;
 }
 
@@ -401,22 +404,19 @@ static enum format choose_format(const char *resp,
 				 enum format format)
 {
 	/* If they specify a format, that's what we use. */
-	if (format != DEFAULT_FORMAT)
+	if (format != DEFAULT_FORMAT) {
+		/* But humans don't want to see the format hint! */
+		if (format == HUMAN)
+			delete_format_hint(resp, toks);
 		return format;
+	}
 
 	/* This works best when we order it. */
 	if (streq(method, "help") && command == NULL)
 		format = HELPLIST;
-	else {
-		const jsmntok_t *result = json_get_member(resp, *toks, "result");
-		if (result)
-			/* Use offset of result to get non-const ptr */
-			format = delete_format_hint(resp, toks,
-						    /* const-washing */
-						    *toks + (result - *toks));
-		else
-			format = JSON;
-	}
+	else
+		format = delete_format_hint(resp, toks);
+
 	return format;
 }
 

tests/test_misc.py

@@ -1052,6 +1052,17 @@ def test_cli(node_factory):
                      '   ]',
                      '}']
 
+    # Make sure we omit top-levels and don't include format hint, when -H forced
+    out = subprocess.check_output(['cli/lightning-cli',
+                                   '--network={}'.format(TEST_NETWORK),
+                                   '--lightning-dir={}'
+                                   .format(l1.daemon.lightning_dir),
+                                   '-H',
+                                   'help']).decode('utf-8')
+    lines = out.splitlines()
+    assert [l for l in lines if l.startswith('help=')] == []
+    assert [l for l in lines if l.startswith('format-hint=')] == []
+
 
 def test_daemon_option(node_factory):
     """