Watch for changes to source files

We used to only watch for file creation and deletion because that might modify build settings but for background indexing, we also need to watch for changes to the files, so we can invalidate the up-to-date status of the target.

Author: ahoppen

Sources/SourceKitLSP/SourceKitLSPServer.swift

@@ -1470,7 +1470,7 @@ extension SourceKitLSPServer {
     // dynamic registration of watch patterns.
     // This must be a superset of the files that return true for SwiftPM's `Workspace.fileAffectsSwiftOrClangBuildSettings`.
     var watchers = FileRuleDescription.builtinRules.flatMap({ $0.fileTypes }).map { fileExtension in
-      return FileSystemWatcher(globPattern: "**/*.\(fileExtension)", kind: [.create, .delete])
+      return FileSystemWatcher(globPattern: "**/*.\(fileExtension)", kind: [.create, .change, .delete])
     }
     watchers.append(FileSystemWatcher(globPattern: "**/Package.swift", kind: [.change]))
     watchers.append(FileSystemWatcher(globPattern: "**/compile_commands.json", kind: [.create, .change, .delete]))