Introduce new diff parser for blob diffs
The current diff parser in Gitaly requires git-diff(1)
to produce "raw" output in order to have context of call the patches that will be computed and parsed. With batch blob diff generation the "raw" output can not longer be used because there will no longer be upfront context of all the patches being computed. Instead, patches will be computed and parsed on demand.
Something to consider here is how patches will be delimited