Disable alternate diff drivers in setup script

[chrisvanpatten]

If you have an alternate diff driver set up (in my case it's a small shell script wrapping vimdiff), the setup script can hang when running git diff --exit-code package.json to check if package.json has changed. (Basically, Vim can't load the UI so you can close it and return the exit code, and throws up an error.)

This change adds the --no-ext-diff flag to those checks, which disables any external/custom diff drivers and uses git's built-in driver instead.

It's a small corner case but enforcing the use of git's internal diff driver should help guarantee slightly more consistency in general.

Testing

Run git diff --exit-code package.json and git diff --no-ext-diff --exit-code package.json and confirm they return the same exit code.

Or run the whole setup script (or just ./bin/install-node-nvm.sh) if you want 🤷‍♂️

[tofumatt]

Huh, today I learned!

Makes sense to me; return codes are the same to me. 👍

[tofumatt]

Ah, quick note though: could you look through our scripts and ensure we are using --no-ext-diff everywhere? I think we use it elsewhere to do some checks; it's probably worth doing it this way everywhere.

[tofumatt]

Haha, you are TOO FAST. 😆

[chrisvanpatten]

@tofumatt I'm on the ball this morning 😂🏃‍♂️