Readd printHelp function back

But update signature to take a writer. This is a backwards incompatible
change for those overriding the HelpPrinter, but the hope is that this
feature is largely unused and the usage is easily updated.

app.go

@@ -5,9 +5,6 @@ import (
 	"io"
 	"io/ioutil"
 	"os"
-	"strings"
-	"text/tabwriter"
-	"text/template"
 	"time"
 )
 
@@ -83,26 +80,6 @@ func (a *App) Run(arguments []string) (err error) {
 		a.Authors = append(a.Authors, Author{Name: a.Author, Email: a.Email})
 	}
 
-	if HelpPrinter == nil {
-		defer func() {
-			HelpPrinter = nil
-		}()
-
-		HelpPrinter = func(templ string, data interface{}) {
-			funcMap := template.FuncMap{
-				"join": strings.Join,
-			}
-
-			w := tabwriter.NewWriter(a.Writer, 0, 8, 1, '\t', 0)
-			t := template.Must(template.New("help").Funcs(funcMap).Parse(templ))
-			err := t.Execute(w, data)
-			if err != nil {
-				panic(err)
-			}
-			w.Flush()
-		}
-	}
-
 	// append help to commands
 	if a.Command(helpCommand.Name) == nil && !a.HideHelp {
 		a.Commands = append(a.Commands, helpCommand)

app_test.go

@@ -3,6 +3,7 @@ package cli_test
 import (
 	"flag"
 	"fmt"
+	"io"
 	"os"
 	"testing"
 
@@ -537,7 +538,7 @@ func TestAppHelpPrinter(t *testing.T) {
 	}()
 
 	var wasCalled = false
-	cli.HelpPrinter = func(template string, data interface{}) {
+	cli.HelpPrinter = func(w io.Writer, template string, data interface{}) {
 		wasCalled = true
 	}
 

help.go

@@ -1,6 +1,12 @@
 package cli
 
-import "fmt"
+import (
+	"fmt"
+	"io"
+	"strings"
+	"text/tabwriter"
+	"text/template"
+)
 
 // The text template for the Default help topic.
 // cli.go uses text/template to render templates. You can
@@ -87,16 +93,16 @@ var helpSubcommand = Command{
 	},
 }
 
-// Prints help for the App
-type helpPrinter func(templ string, data interface{})
+// Prints help for the App or Command
+type helpPrinter func(w io.Writer, templ string, data interface{})
 
-var HelpPrinter helpPrinter = nil
+var HelpPrinter helpPrinter = printHelp
 
 // Prints version for the App
 var VersionPrinter = printVersion
 
 func ShowAppHelp(c *Context) {
-	HelpPrinter(AppHelpTemplate, c.App)
+	HelpPrinter(c.App.Writer, AppHelpTemplate, c.App)
 }
 
 // Prints the list of subcommands as the default app completion method
@@ -109,24 +115,24 @@ func DefaultAppComplete(c *Context) {
 }
 
 // Prints help for the given command
-func ShowCommandHelp(c *Context, command string) {
+func ShowCommandHelp(ctx *Context, command string) {
 	// show the subcommand help for a command with subcommands
 	if command == "" {
-		HelpPrinter(SubcommandHelpTemplate, c.App)
+		HelpPrinter(ctx.App.Writer, SubcommandHelpTemplate, ctx.App)
 		return
 	}
 
-	for _, c := range c.App.Commands {
+	for _, c := range ctx.App.Commands {
 		if c.HasName(command) {
-			HelpPrinter(CommandHelpTemplate, c)
+			HelpPrinter(ctx.App.Writer, CommandHelpTemplate, c)
 			return
 		}
 	}
 
-	if c.App.CommandNotFound != nil {
-		c.App.CommandNotFound(c, command)
+	if ctx.App.CommandNotFound != nil {
+		ctx.App.CommandNotFound(ctx, command)
 	} else {
-		fmt.Fprintf(c.App.Writer, "No help topic for '%v'\n", command)
+		fmt.Fprintf(ctx.App.Writer, "No help topic for '%v'\n", command)
 	}
 }
 
@@ -160,6 +166,20 @@ func ShowCommandCompletions(ctx *Context, command string) {
 	}
 }
 
+func printHelp(out io.Writer, templ string, data interface{}) {
+	funcMap := template.FuncMap{
+		"join": strings.Join,
+	}
+
+	w := tabwriter.NewWriter(out, 0, 8, 1, '\t', 0)
+	t := template.Must(template.New("help").Funcs(funcMap).Parse(templ))
+	err := t.Execute(w, data)
+	if err != nil {
+		panic(err)
+	}
+	w.Flush()
+}
+
 func checkVersion(c *Context) bool {
 	if c.GlobalBool("version") {
 		ShowVersion(c)