Fix ghost drive letter after CLI dismount (GH #337, GH #1426) (#1658)

When dismounting via CLI (/d /q /s), SHChangeNotify is called without
SHCNF_FLUSH flag, making it asynchronous. The process exits before
Explorer processes the notification, leaving a phantom drive letter
visible in Explorer as an inaccessible Local Disk until reboot.

Add SHCNF_FLUSH in Silent (CLI) mode to force synchronous shell
notification processing in both single-volume (UnmountVolumeBase)
and dismount-all (DismountAll) code paths. The flush is only added
in CLI mode to avoid adding latency to interactive GUI operations.

Co-authored-by: Contributor <contributor@example.com>

src/Common/Dlgcode.c

@@ -9357,6 +9357,18 @@ retry:
 
 	BroadcastDeviceChange (DBT_DEVICEREMOVECOMPLETE, nDosDriveNo, 0);
 
+	/* GH #337, GH #1426: When running in silent/CLI mode, the process may
+	   exit immediately after unmount. BroadcastDeviceChange sends
+	   SHChangeNotify asynchronously, so Explorer may not process the drive
+	   removal before the process exits, leaving a ghost drive letter.
+	   Re-send the notification with SHCNF_FLUSH to force synchronous
+	   processing by Explorer before we return. */
+	if (Silent)
+	{
+		wchar_t root[] = { (wchar_t) (nDosDriveNo + L'A'), L':', L'\\', 0 };
+		SHChangeNotify (SHCNE_DRIVEREMOVED, SHCNF_PATH | SHCNF_FLUSH, root, NULL);
+	}
+
 	return TRUE;
 }
 

src/Mount/Mount.c

@@ -5763,6 +5763,22 @@ retry:
 
 	BroadcastDeviceChange (DBT_DEVICEREMOVECOMPLETE, 0, prevMountList.ulMountedDrives & ~mountList.ulMountedDrives);
 
+	/* GH #337, GH #1426: Flush shell notifications synchronously in
+	   silent/CLI mode to prevent ghost drive letters when the process
+	   exits immediately after dismount. */
+	if (Silent)
+	{
+		DWORD removedDrives = prevMountList.ulMountedDrives & ~mountList.ulMountedDrives;
+		for (i = 0; i < 26; i++)
+		{
+			if (removedDrives & (1 << i))
+			{
+				wchar_t root[] = { (wchar_t) (i + L'A'), L':', L'\\', 0 };
+				SHChangeNotify (SHCNE_DRIVEREMOVED, SHCNF_PATH | SHCNF_FLUSH, root, NULL);
+			}
+		}
+	}
+
 	RefreshMainDlg (hwndDlg);
 
 	NormalCursor();