Windows updater: wait for installer and relaunch

Make the Windows deferred update launcher wait for the installer to finish and relaunch the correct PakFu binary. Pass the current app path into the generated batch script, add APP/APP_TO_START handling, use /wait when launching MSI or installer artifacts, and prefer the installer-managed %LOCALAPPDATA%\PakFu\pakfu.exe if present. Also fix the startDetached invocation to execute the composed command string.

Author: themuffinator

README.md

@@ -231,6 +231,10 @@ Selector support:
 ## Updates and Releases
 PakFu can check GitHub Releases at runtime and from CLI.
 
+GUI updater install handoff:
+- Windows: `Install and Restart` waits for installer completion, then relaunches PakFu (preferring the installer-managed `%LOCALAPPDATA%\PakFu\pakfu.exe` after MSI updates).
+- macOS/Linux: PakFu exits and starts the downloaded installer artifact (`.pkg` / `.AppImage`) after shutdown.
+
 Build-time updater config:
 - `-Dgithub_repo=themuffinator/PakFu` (default; see `meson_options.txt`)
 - `-Dupdate_channel=stable|beta|dev` (default: `stable`; full releases only; see `meson_options.txt`)

src/update/update_service.cpp

@@ -132,6 +132,7 @@ namespace {
   }
 
   const QString installer_absolute_path = installer_info.absoluteFilePath();
+  const QString app_absolute_path = QFileInfo(QCoreApplication::applicationFilePath()).absoluteFilePath();
 
   const QString temp_dir = QStandardPaths::writableLocation(QStandardPaths::TempLocation);
   if (temp_dir.isEmpty()) {
@@ -164,6 +165,8 @@ namespace {
     "setlocal EnableExtensions\r\n"
     "set \"PID=%~1\"\r\n"
     "set \"INSTALLER=%~f2\"\r\n"
+    "set \"APP=%~f3\"\r\n"
+    "set \"APP_TO_START=%APP%\"\r\n"
     "set \"EXT=%~x2\"\r\n"
     ":waitloop\r\n"
     "tasklist /FI \"PID eq %PID%\" 2>NUL | findstr /I \"%PID%\" >NUL\r\n"
@@ -172,9 +175,13 @@ namespace {
     "  goto waitloop\r\n"
     ")\r\n"
     "if /I \"%EXT%\"==\".msi\" (\r\n"
-    "  start \"\" msiexec.exe /i \"%INSTALLER%\"\r\n"
+    "  start \"\" /wait msiexec.exe /i \"%INSTALLER%\"\r\n"
+    "  if exist \"%LOCALAPPDATA%\\PakFu\\pakfu.exe\" set \"APP_TO_START=%LOCALAPPDATA%\\PakFu\\pakfu.exe\"\r\n"
     ") else (\r\n"
-    "  start \"\" \"%INSTALLER%\"\r\n"
+    "  start \"\" /wait \"%INSTALLER%\"\r\n"
+    ")\r\n"
+    "if exist \"%APP_TO_START%\" (\r\n"
+    "  start \"\" \"%APP_TO_START%\"\r\n"
     ")\r\n"
     "start \"\" /B cmd.exe /C del /F /Q \"%~f0\" >NUL 2>&1\r\n"
     "endlocal\r\n";
@@ -183,8 +190,11 @@ namespace {
 
   const QString script_path = QDir::toNativeSeparators(script.fileName());
   const QString installer_arg = QDir::toNativeSeparators(installer_absolute_path);
+  const QString app_arg = QDir::toNativeSeparators(app_absolute_path);
+  const QString cmd = QString("\"\"%1\" %2 \"%3\" \"%4\"\"")
+                        .arg(script_path, QString::number(pid), installer_arg, app_arg);
 
-  if (!QProcess::startDetached("cmd.exe", {"/C", script_path, QString::number(pid), installer_arg})) {
+  if (!QProcess::startDetached("cmd.exe", {"/C", cmd})) {
     if (error) {
       *error = "Unable to start deferred update launcher.";
     }