Diff –git unknown option

Git 2.9 was released earlier this year which included the experimental flag --compaction-heuristic on the git diff command:

In 2.9, Git's diff engine learned a new heuristic: it tries to keep hunk boundaries at blank lines, shifting the hunk "up" whenever the bottom of the hunk matches the bottom of the preceding context, until we hit a blank line.

I don't think GitHub has it enabled for diffs on the web UI for Pull Requests and comparisons, but you can do it locally. I'd recommend using it in conjunction with --word-diff if you need that level of granularity.

More details available on the GitHub blog: https://github.com/blog/2188-git-2-9-has-been-released

This seems to be from prezto defining a function overriding diff. It may well have a way of disabling that, but I don't know what it is (but ericbn does!). You have a few options:

• /usr/bin/diff or command diff will both run the diff command, rather than the function.
• unset -f diff will remove the diff function. You could put that in your shell configuration.
• As you've found, if colordiff is installed it will be used in preference to git diff by the function.
• Finally, you can remove or rename the function from that file itself.

This really seems like a misfeature in prezto.