Add files via upload

tty.go

@@ -0,0 +1,12 @@
+package main
+
+import "os"
+
+// isTerminal reports whether stdout is a TTY. Stdlib-only check via FileMode.
+func isTerminal() bool {
+	fi, err := os.Stdout.Stat()
+	if err != nil || fi == nil {
+		return false
+	}
+	return fi.Mode()&os.ModeCharDevice != 0
+}