fix(git_chain): restore captured terminal state on exit

Author: orestesgaolin

git_chain/CHANGELOG.md

@@ -2,7 +2,7 @@
 
 **Bug Fixes**
 
-- fix mangled / "stairstepped" shell output after a sync that opened the merge tool. nocterm and `git mergetool` can leave the terminal with output post-processing (`ONLCR`) disabled, which Dart's stdin API can't restore; git_chain now runs `stty sane` on exit to put the terminal back.
+- restore the terminal to its exact pre-launch state on exit by snapshotting `stty -g` before the TUI and replaying it afterwards. Fixes Ctrl+C not working, no echo, and "stairstepped" output (`ONLCR` off) left behind by nocterm / `git mergetool` — none of which Dart's stdin API can restore on its own.
 
 ## 0.5.5
 

git_chain/lib/src/commands/tui_command.dart

@@ -28,6 +28,10 @@ class TuiCommand extends Command<void> {
     // If launched inside a git repo, register it and jump straight to it.
     final discovered = await service.registerRepo(Directory.current.path);
 
+    // Snapshot the terminal before nocterm touches it, so we can restore the
+    // exact original modes (echo, Ctrl+C/ISIG, ONLCR) on exit.
+    captureTerminalState();
+
     final intent = AppIntent();
     await runApp(GitChainApp(
       db: db,

git_chain/lib/src/util/terminal_input.dart

@@ -42,17 +42,39 @@ void drainTerminalInput() {
   }
 }
 
-/// Restores sane terminal modes (echo, canonical input, and crucially output
-/// post-processing / `ONLCR`).
+/// The terminal settings captured before the TUI started, used to restore the
+/// exact original state on exit.
+String? _savedTtyState;
+
+/// Snapshots the controlling terminal's settings (`stty -g`) so they can be
+/// restored verbatim later. Call once, before `runApp`.
+void captureTerminalState() {
+  if (!(Platform.isMacOS || Platform.isLinux)) return;
+  try {
+    final result = Process.runSync('sh', ['-c', 'stty -g < /dev/tty']);
+    if (result.exitCode == 0) {
+      final state = (result.stdout as String).trim();
+      if (state.isNotEmpty) _savedTtyState = state;
+    }
+  } catch (_) {
+    // Best-effort.
+  }
+}
+
+/// Restores the terminal to the exact state captured by [captureTerminalState]
+/// (echo, canonical input, signal handling / Ctrl+C, output post-processing /
+/// `ONLCR`). Falls back to `stty sane` if no snapshot was taken.
 ///
-/// nocterm and `git mergetool` can leave the terminal with output processing
-/// disabled, which makes subsequent shell output "stairstep" (line feeds with
-/// no carriage return). Dart's stdin API only restores input flags, so we shell
-/// out to `stty sane` against the controlling terminal.
+/// Dart's stdin API only restores input flags, and nocterm / `git mergetool`
+/// can leave the terminal with signals or output processing disabled — which
+/// breaks Ctrl+C and makes shell output "stairstep". Restoring the full
+/// snapshot fixes all of it at once.
 Future<void> restoreTerminalModes() async {
   if (!(Platform.isMacOS || Platform.isLinux)) return;
+  final saved = _savedTtyState;
+  final cmd = saved != null ? 'stty $saved < /dev/tty' : 'stty sane < /dev/tty';
   try {
-    await Process.run('sh', ['-c', 'stty sane < /dev/tty']);
+    await Process.run('sh', ['-c', cmd]);
   } catch (_) {
     // Best-effort.
   }