Merge pull request #20 from codegangsta/JMS-5

Improved help by allowing help topics for subcommands

help.go

@@ -7,12 +7,10 @@ import (
 	"text/template"
 )
 
-var helpCommand = Command{
-	Name:      "help",
-	ShortName: "h",
-	Usage:     "Shows a list of commands or help for one command",
-	Action: func(c *Context) {
-		helpTemplate := `NAME:
+// The text template for the Default help topic.
+// cli.go uses text/template to render templates. You can
+// render custom help text by setting this variable.
+var AppHelpTemplate = `NAME:
    {{.Name}} - {{.Usage}}
 
 USAGE:
@@ -29,11 +27,59 @@ GLOBAL OPTIONS:
    {{end}}
 `
 
+// The text template for the command help topic.
+// cli.go uses text/template to render templates. You can
+// render custom help text by setting this variable.
+var CommandHelpTemplate = `NAME:
+   {{.Name}} - {{.Usage}}
+
+USAGE:
+   command {{.Name}} [command options] [arguments...]
+
+DESCRIPTION:
+   {{.Description}}
+
+OPTIONS:
+   {{range .Flags}}{{.}}
+   {{end}}
+`
+
+var helpCommand = Command{
+	Name:      "help",
+	ShortName: "h",
+	Usage:     "Shows a list of commands or help for one command",
+	Action: func(c *Context) {
+		args := c.Args()
+		if len(args) > 0 {
+			showCommandHelp(c)
+		} else {
+			showAppHelp(c)
+		}
+	},
+}
+
+func showAppHelp(c *Context) {
+	printHelp(AppHelpTemplate, c.App)
+}
+
+func showCommandHelp(c *Context) {
+	name := c.Args()[0]
+	for _, c := range c.App.Commands {
+		if c.HasName(name) {
+			printHelp(CommandHelpTemplate, c)
+			return
+		}
+	}
+
+	fmt.Printf("No help topic for '%v'\n", name)
+	os.Exit(1)
+}
+
+func printHelp(templ string, data interface{}) {
 	w := tabwriter.NewWriter(os.Stdout, 0, 8, 1, '\t', 0)
-		t := template.Must(template.New("help").Parse(helpTemplate))
-		t.Execute(w, c.App)
+	t := template.Must(template.New("help").Parse(templ))
+	t.Execute(w, data)
 	w.Flush()
-	},
 }
 
 func showVersion(c *Context) {