[feat] - tmp file diffs (#2306)

* Write large diffs to tmp files

* address comments

* Move bufferedfilewriter to own pkg

* update test

* swallow write err

* use buffer pool

* use size vs len

* use interface

* fix test

* update comments

* fix test

* remove unused

* remove

* remove unused

* move parser and commit struct closer to where they are used

* linter change

* add more kvp pairs to error

* fix test

* update

* address comments

* remove bufferedfile writer

* address comments

* adjust interface

* fix finalize

* address comments

* lint

* remove guard

* fix

* add TODO