send uris for git.mergeChanges context as objects

That way they undergo uri transformation and the setContext-command will stringify them so that everything works, fixes microsoft#159837

Author: jrieken

extensions/git/src/repository.ts

@@ -2056,7 +2056,7 @@ export class Repository implements Disposable {
 		this.setCountBadge();
 
 		// set mergeChanges context
-		commands.executeCommand('setContext', 'git.mergeChanges', merge.map(item => item.resourceUri.toString()));
+		commands.executeCommand('setContext', 'git.mergeChanges', merge.map(item => item.resourceUri));
 
 		this._onDidChangeStatus.fire();