fix off-by-one error in magit-wash-commit
fix section's title being used where info (file) should have been

This fixes 2 bugs:
- "Can't visit deleted file: diff --git a/magit.el b/magit.el"
- Empty buffers when calling magit-ediff on a hunk in magit-commit-mode

"info" slot should probably be renamed into "file"
Merge branch 'pr/fix-ediff-and-visit-item'