flag: export commandLine, the previously internal default FlagSet

s/commandLine/CommandLine/g

Fixes #4209.

R=golang-dev, dsymonds, bradfitz
CC=golang-dev
https://golang.org/cl/12587043

src/pkg/flag/export_test.go

@@ -12,11 +12,6 @@ import "os"
 // After calling ResetForTesting, parse errors in flag handling will not
 // exit the program.
 func ResetForTesting(usage func()) {
-	commandLine = NewFlagSet(os.Args[0], ContinueOnError)
+	CommandLine = NewFlagSet(os.Args[0], ContinueOnError)
 	Usage = usage
 }
-
-// CommandLine returns the default FlagSet.
-func CommandLine() *FlagSet {
-	return commandLine
-}

src/pkg/flag/flag_test.go

@@ -139,7 +139,7 @@ func TestGet(t *testing.T) {
 func TestUsage(t *testing.T) {
 	called := false
 	ResetForTesting(func() { called = true })
-	if CommandLine().Parse([]string{"-x"}) == nil {
+	if CommandLine.Parse([]string{"-x"}) == nil {
 		t.Error("parse did not fail for unknown flag")
 	}
 	if !called {
@@ -215,7 +215,7 @@ func testParse(f *FlagSet, t *testing.T) {
 
 func TestParse(t *testing.T) {
 	ResetForTesting(func() { t.Error("bad parse") })
-	testParse(CommandLine(), t)
+	testParse(CommandLine, t)
 }
 
 func TestFlagSetParse(t *testing.T) {
@@ -311,7 +311,7 @@ func TestChangingArgs(t *testing.T) {
 	defer func() { os.Args = oldArgs }()
 	os.Args = []string{"cmd", "-before", "subcmd", "-after", "args"}
 	before := Bool("before", false, "")
-	if err := CommandLine().Parse(os.Args[1:]); err != nil {
+	if err := CommandLine.Parse(os.Args[1:]); err != nil {
 		t.Fatal(err)
 	}
 	cmd := Arg(0)