cmake: Add --help-policy-list option

All the other --help-<item> options have a corresponding option
--help-<item>-list.  Add one for --help-policy.

Source/cmDocumentation.cxx

@@ -371,6 +371,9 @@ bool cmDocumentation::PrintDocumentation(Type ht, std::ostream& os,
         this->PrintDocumentationList(os,i->c_str());
         }
       return true;
+    case cmDocumentation::PolicyList:
+      this->PrintDocumentationList(os,"Policies");
+      return true;
     case cmDocumentation::Full:
       return this->PrintDocumentationFull(os);
     case cmDocumentation::Modules:
@@ -1256,6 +1259,12 @@ bool cmDocumentation::CheckOptions(int argc, const char* const* argv,
       GET_OPT_ARGUMENT(help.Filename);
       help.HelpForm = cmDocumentation::TextForm;
       }
+    else if(strcmp(argv[i], "--help-policy-list") == 0)
+      {
+      help.HelpType = cmDocumentation::PolicyList;
+      GET_OPT_ARGUMENT(help.Filename);
+      help.HelpForm = cmDocumentation::TextForm;
+      }
     else if(strcmp(argv[i], "--copyright") == 0)
       {
       help.HelpType = cmDocumentation::Copyright;

Source/cmDocumentationFormatter.h

@@ -26,7 +26,7 @@ public:
   /** Types of help provided.  */
   enum Type
   { None, Usage, Single, SingleModule, SingleProperty, SingleVariable,
-    List, ModuleList, PropertyList, VariableList,
+    List, ModuleList, PropertyList, VariableList, PolicyList,
     Full, Properties, Variables, Modules, CustomModules, Commands,
     CompatCommands, Copyright, Version, Policies, SinglePolicy };
 

Source/cmakemain.cxx

@@ -195,6 +195,12 @@ static const char * cmDocumentationOptions[][3] =
    "If a file is specified, the documentation is written into and the output "
    "format is determined depending on the filename suffix. Supported are man "
    "page, HTML, DocBook and plain text."},
+  {"--help-policy-list [file]", "List available policies and exit.",
+   "The list contains all policies for which help may be obtained by using "
+   "the --help-policy argument followed by a policy name. "
+   "If a file is specified, the documentation is written into and the output "
+   "format is determined depending on the filename suffix. Supported are man "
+   "page, HTML, DocBook and plain text."},
   {"--help-policies [file]", "Print help for all policies and exit.",
    "Full documentation for all policies is displayed."
    "If a file is specified, the documentation is written into and the output "