Don't indent line if all we're outputting is ANSI sequences

indent.go

@@ -13,32 +13,44 @@ type IndentWriter struct {
 	IndentFunc IndentFunc
 
 	skipIndent bool
+	ansi       bool
 }
 
 // Write is used to write content to the indent buffer.
 func (w *IndentWriter) Write(b []byte) (int, error) {
 	for _, c := range string(b) {
-		if !w.skipIndent {
-			if w.IndentFunc != nil {
-				for i := 0; i < int(w.Indent); i++ {
-					w.IndentFunc(w.Forward)
-				}
-			} else {
-				_, err := w.Forward.Write([]byte(strings.Repeat(" ", int(w.Indent))))
-				if err != nil {
-					return 0, err
+		if c == '\x1B' {
+			// ANSI escape sequence
+			w.ansi = true
+		} else if w.ansi {
+			if (c >= 0x41 && c <= 0x5a) || (c >= 0x61 && c <= 0x7a) {
+				// ANSI sequence terminated
+				w.ansi = false
+			}
+		} else {
+			if !w.skipIndent {
+				w.Forward.ResetAnsi()
+				if w.IndentFunc != nil {
+					for i := 0; i < int(w.Indent); i++ {
+						w.IndentFunc(w.Forward)
+					}
+				} else {
+					_, err := w.Forward.Write([]byte(strings.Repeat(" ", int(w.Indent))))
+					if err != nil {
+						return 0, err
+					}
 				}
+
+				w.skipIndent = true
+				w.Forward.RestoreAnsi()
 			}
 
-			w.Forward.RestoreAnsi()
-			w.skipIndent = true
+			if c == '\n' {
+				// end of current line
+				w.skipIndent = false
+			}
 		}
 
-		if c == '\n' {
-			// end of current line
-			w.skipIndent = false
-			w.Forward.ResetAnsi()
-		}
 		_, err := w.Forward.Write([]byte(string(c)))
 		if err != nil {
 			return 0, err