The git-diff npm package produces a simplified diff format (lines
prefixed with +/-/space, no chunk headers), which is incompatible with
parse-diff. This caused the json.files field in the change tracking
diff response to always be empty.
Replace git-diff with the diff library's createTwoFilesPatch, which
produces standard unified diff format with proper @@, ---, and +++
headers that parse-diff can parse correctly.
Co-Authored-By: micahstairs <micah@sideguide.dev>
85de0dae4e