Add --color=false flag to disable colored output

internal/logger/logger.go

@@ -25,6 +25,7 @@ type Logger struct {
 	Stdout  io.Writer
 	Stderr  io.Writer
 	Verbose bool
+	Color   bool
 }
 
 // Outf prints stuff to STDOUT.
@@ -32,6 +33,9 @@ func (l *Logger) Outf(print PrintFunc, s string, args ...interface{}) {
 	if len(args) == 0 {
 		s, args = "%s", []interface{}{s}
 	}
+	if !l.Color {
+		print = Default
+	}
 	print(l.Stdout, s+"\n", args...)
 }
 
@@ -47,6 +51,9 @@ func (l *Logger) Errf(print PrintFunc, s string, args ...interface{}) {
 	if len(args) == 0 {
 		s, args = "%s", []interface{}{s}
 	}
+	if !l.Color {
+		print = Default
+	}
 	print(l.Stderr, s+"\n", args...)
 }