WinMerge provides rudimentary VSS integration by checking the read-only status of the file. If VSS integration is enabled, and the file you are changing is marked read-only, WinMerge will display the CheckOut dialog when when you attempt to save the file. Simply enter the SourceSafe path to the file's project (in VSS syntax) and click the Check Out button.
Unfortunately, VSS is horribly silent about error conditions (other than the fact that one occurred). If an operation fails, one of the following conditions could be at fault:
To enable VSS support, select Options from the Edit menu, then click the SourceSafe tab and do the following:
1. Select the version of Visual SourceSafe
2. Use the Browse button to locate your local copy of SS.EXE, which is part of the VSS installation. WinMerge attempts to detect the location from the registry, but may sometimes fail to find the correct path.