Allow diff limits to be configurable
Description
We set hard diff size limits due to performance and other reasons.
- Hard diff rendering limits: https://gitlab.com/gitlab-org/gitlab-ee/blob/master/app/models/commit.rb#L20-22
- gitlab_git diff size check: https://gitlab.com/gitlab-org/gitlab_git/blob/master/lib/gitlab_git/diff.rb#L200-218
Proposal
Make diff size limits a configurable value.