"Now that is a lot of code! There's simply too much in this diff for us to render it all."
This message left me with bad feels (happened on a package-lock.json).
1) Don't act surprised/incredulous - it's judgemental and makes people feel bad.
2) Don't treat the size as an excuse "There's simply too much" is a judgemental "you fucked up" whereas something like "We've limited diffs to X lines" would be a non-judgemental "we can't support you"
3) Offer a solution "To view these changes, please clone the repository and run