Restored logic in color writer to distinguish the underlying terminal…

… type

log/term/colorwriter_windows.go

@@ -25,7 +25,7 @@ type colorWriter struct {
 // platform support for ANSI color codes. If w is not a terminal it is
 // returned unmodified.
 func NewColorWriter(w io.Writer) io.Writer {
-	if !IsTerminal(w) {
+	if !IsConsole(w) {
 		return w
 	}
 

log/term/terminal_windows.go

@@ -28,6 +28,11 @@ const (
 
 // IsTerminal returns true if w writes to a terminal.
 func IsTerminal(w io.Writer) bool {
+	return IsConsole(w) || IsMSYSTerminal(w)
+}
+
+// IsConsole returns true if w writes to a Windows console.
+func IsConsole(w io.Writer) bool {
 	var handle syscall.Handle
 
 	if fw, ok := w.(fder); ok {
@@ -40,8 +45,20 @@ func IsTerminal(w io.Writer) bool {
 	var st uint32
 
 	// If the terminal is a Windows console, succeed right away.
-	if err := syscall.GetConsoleMode(handle, &st); err == nil && st != 0 {
-		return true
+	err := syscall.GetConsoleMode(handle, &st)
+
+	return (err == nil && st != 0)
+}
+
+// IsMSYSTerminal returns true if w writes to a MSYS/MSYS2 terminal.
+func IsMSYSTerminal(w io.Writer) bool {
+	var handle syscall.Handle
+
+	if fw, ok := w.(fder); ok {
+		handle = syscall.Handle(fw.Fd())
+	} else {
+		// The writer has no file-descriptor and so can't be a terminal.
+		return false
 	}
 
 	// The terminal is not a cmd.exe terminal, let's try to detect MSYS2 terminals.

log/term/terminal_windows_test.go

@@ -54,3 +54,18 @@ func TestIsTerminal(t *testing.T) {
 		t.Errorf("output is supposed to be a terminal")
 	}
 }
+
+func TestIsConsole(t *testing.T) {
+	// This is necessary because depending on whether `go test` is called with
+	// the `-v` option, stdout will or will not be bound, changing the behavior
+	// of the test. So we refer to it directly to avoid flakyness.
+	handle := getConsoleHandle()
+
+	writer := &myWriter{
+		fd: uintptr(handle),
+	}
+
+	if !IsConsole(writer) {
+		t.Errorf("output is supposed to be a console")
+	}
+}