Regression in 1.3.4: discarding file changes during rewrite deletes the whole file

[jfirebaugh]

To reproduce:

1. Select "Rewrite..." on some commit
2. Click "Discard File Changes..."

Expected result: File is removed from diff
Actual result: File is deleted entirely in diff

Works as expected in 1.3.2.

[lucasderraugh]

Will be addressed in 1.3.5.

We made changes in e060ece that were meant to assist in bulk discard/stage operations, but there were some bugs in the handling of that.

Thanks for reporting!