curl.1: make help, version and manual sections "custom"

Instead of using "multi: boolean", as these are slightly special as in
they do are not enable/disable ones.

Fixes #10490
Reported-by: u20221022 on github
Closes #10497

docs/cmdline-opts/MANPAGE.md

@@ -31,7 +31,7 @@ Each file has a set of meta-data and a body of text.
     Help: (short text for the --help output for this option)
     Long: (long form name, without dashes)
     Magic: (description of "magic" options)
-    Multi: single/append/boolean/mutex (if used more than once)
+    Multi: single/append/boolean/mutex/custom (if used more than once)
     Mutexed: (space separated list of options this overrides, no dashes)
     Protocols: (space separated list for which protocols this option works)
     Requires: (space separated list of features this requires, no dashes)

docs/cmdline-opts/gen.pl

@@ -270,10 +270,6 @@ sub single {
                 print STDERR "ERROR: no 'Long:' in $f\n";
                 return 1;
             }
-            if($multi !~ /(single|append|boolean|mutex)/) {
-                print STDERR "ERROR: bad 'Multi:' in $f\n";
-                return 1;
-            }
             if(!$category) {
                 print STDERR "ERROR: no 'Category:' in $f\n";
                 return 2;
@@ -375,6 +371,13 @@ sub single {
         push @extra,
             "\nProviding --$long multiple times has no extra effect.\n";
     }
+    elsif($multi eq "custom") {
+        ; # left for the text to describe
+    }
+    else {
+        print STDERR "$f:$line:1:ERROR: unrecognized Multi: '$multi'\n";
+        return 2;
+    }
 
     printdesc(@extra);
 
@@ -622,7 +625,9 @@ sub mainpage {
         $ret += single($f, 0);
     }
 
-    header("page-footer");
+    if(!$ret) {
+        header("page-footer");
+    }
     exit $ret if($ret);
 }
 

docs/cmdline-opts/help.d

@@ -8,7 +8,7 @@ Category: important curl
 Example: --help all
 Added: 4.0
 See-also: verbose
-Multi: boolean
+Multi: custom
 ---
 Usage help. This lists all commands of the <category>.
 If no arg was provided, curl will display the most important

docs/cmdline-opts/manual.d

@@ -7,6 +7,6 @@ Category: curl
 Example: --manual
 Added: 5.2
 See-also: verbose libcurl trace
-Multi: boolean
+Multi: custom
 ---
 Manual. Display the huge help text.

docs/cmdline-opts/version.d

@@ -7,7 +7,7 @@ Category: important curl
 Example: --version
 Added: 4.0
 See-also: help manual
-Multi: boolean
+Multi: custom
 ---
 Displays information about curl and the libcurl version it uses.