Allow the diff kitten to work even if stdout/stdin are redirected

Now directly opens /dev/tty

kittens/diff/main.py

@@ -399,6 +399,11 @@ def main(args):
     opts = init_config(args)
     set_diff_command(opts.diff_cmd)
     lines_for_path.replace_tab_by = opts.replace_tab_by
+    # Ensure the kitten works even when stdin/stdout are redirected
+    if not sys.stdin.isatty():
+        sys.stdin = open('/dev/tty')
+    if not sys.stdout.isatty():
+        sys.stdout = open('/dev/tty', 'w')
 
     loop = Loop()
     handler = DiffHandler(args, opts, left, right)