Add additional points to configure help output

Summary: Sometimes tools need to output a little more help context before or after help.

Reviewed By: yfeldblum

Differential Revision: D4719112

fbshipit-source-id: e6f59312d722e0669053644d862c81758855b538

folly/experimental/NestedCommandLineApp.cpp

@@ -48,11 +48,15 @@ ProgramExit::ProgramExit(int status, const std::string& msg)
 NestedCommandLineApp::NestedCommandLineApp(
     std::string programName,
     std::string version,
+    std::string programHeading,
+    std::string programHelpFooter,
     InitFunction initFunction)
-  : programName_(std::move(programName)),
-    version_(std::move(version)),
-    initFunction_(std::move(initFunction)),
-    globalOptions_("Global options") {
+    : programName_(std::move(programName)),
+      programHeading_(std::move(programHeading)),
+      programHelpFooter_(std::move(programHelpFooter)),
+      version_(std::move(version)),
+      initFunction_(std::move(initFunction)),
+      globalOptions_("Global options") {
   addCommand("help", "[command]",
              "Display help (globally or for a given command)",
              "Displays help (globally or for a given command).",
@@ -101,8 +105,10 @@ void NestedCommandLineApp::displayHelp(
   if (args.empty()) {
     // General help
     printf(
-        "Usage: %s [global_options...] <command> [command_options...] "
-        "[command_args...]\n\n", programName_.c_str());
+        "%s\nUsage: %s [global_options...] <command> [command_options...] "
+        "[command_args...]\n\n",
+        programHeading_.c_str(),
+        programName_.c_str());
     std::cout << globalOptions_;
     printf("\nAvailable commands:\n");
 
@@ -126,6 +132,7 @@ void NestedCommandLineApp::displayHelp(
                int(maxLen), p.first.c_str(), resolveAlias(p.second).c_str());
       }
     }
+    std::cout << "\n" << programHelpFooter_ << "\n";
   } else {
     // Help for a given command
     auto& p = findCommand(args.front());

folly/experimental/NestedCommandLineApp.h

@@ -67,6 +67,8 @@ class NestedCommandLineApp {
   explicit NestedCommandLineApp(
       std::string programName = std::string(),
       std::string version = std::string(),
+      std::string programHeading = std::string(),
+      std::string programHelpFooter = std::string(),
       InitFunction initFunction = InitFunction());
 
   /**
@@ -142,6 +144,8 @@ class NestedCommandLineApp {
       const std::vector<std::string>& args);
 
   std::string programName_;
+  std::string programHeading_;
+  std::string programHelpFooter_;
   std::string version_;
   InitFunction initFunction_;
   boost::program_options::options_description globalOptions_;