If you have local changes you do not want, click the Restore button next to the change you wish to undo. This removes any local changes you have made to that file.
You will be asked if you’re sure you want to lose your local changes. Click Yes to confirm removal of the local files.
Is something described here not working as you expect it to? It might be a Known Issue. Please check with the Issue Tracker at issuetracker.unity3d.com.