After seeing the following from the command line:
# On branch RB_3.0.10
# Changed but not updated:
# (use \"git add ...\" to update what will b
I've had a similar issue, where it wouldn't allow me to discard files which either does not exist or has been changed. I use Visual Studio at work, and I found that this happens when switching branches while the app is running.
git checkout and trying to discard did not help. It wouldn't work or it would just tell me that I do not have permission.
Solution that worked:
Restarting is a pain, but this worked faster than trying out 100 things.