forego/help.go

package main

import (
  "fmt"
  "log"
  "os"
  "text/template"
)

var cmdHelp = &Command{
  Usage: "help [topic]",
  Long:  `Help shows usage for a command or other topic.`,
}

func init() {
  cmdHelp.Run = runHelp // break init loop
}

func runHelp(cmd *Command, args []string) {
  if len(args) == 0 {
    printUsage()
    return
  }
  if len(args) != 1 {
    log.Fatal("too many arguments")
  }

  for _, cmd := range commands {
    if cmd.Name() == args[0] {
      cmd.printUsage()
      return
    }
  }

  fmt.Fprintf(os.Stderr, "Unknown help topic: %q. Run 'forego help'.\n", args[0])
  os.Exit(2)
}

var usageTemplate = template.Must(template.New("usage").Parse(`
Usage: forego [command] [options] [arguments]
{{range .Commands}}{{if .Runnable}}{{if .List}}
    {{.Name | printf "%-8s"}}  {{.Short}}{{end}}{{end}}{{end}}

Run 'forego help [command]' for details.`[1:]))

func printUsage() {
  usageTemplate.Execute(os.Stdout, struct {
    Commands   []*Command
  }{
    commands,
  })
}

func usage() {
  printUsage()
  os.Exit(2)
}