Add golden.FlagUpdate method

Returns true when the -test.update-golden flag has been set.

Fixes: gotestyourself#205

golden/golden.go

@@ -39,6 +39,11 @@ type helperT interface {
 // The default value may change in a future major release.
 var NormalizeCRLFToLF = os.Getenv("GOTESTTOOLS_GOLDEN_NormalizeCRLFToLF") != "false"
 
+// FlagUpdate returns true when the -test.update-golden flag has been set.
+func FlagUpdate() bool {
+ return *flagUpdate
+}
+
 // Open opens the file in ./testdata
 func Open(t assert.TestingT, filename string) *os.File {
  if ht, ok := t.(helperT); ok {

golden/golden_test.go

@@ -204,3 +204,10 @@ func TestBytesFailure(t *testing.T) {
  assert.Equal(t, result.(failure).FailureMessage(),
  `[53 53 53 53] (actual) != [53 53 53 54] (expected)`+failurePostamble(filename))
 }
+
+func TestFlagUpdate(t *testing.T) {
+ assert.Assert(t, !FlagUpdate())
+ undo := setUpdateFlag()
+ defer undo()
+ assert.Assert(t, FlagUpdate())
+}