Add pre-commit hook that runs prettier

[emdash-ie]

What's changed?

As a convenience, this PR adds a hook which checks the formatting of your files, formatting any which it’s safe to.

Implementation notes

I’ve copied the one I implemented in https://github.com/guardian/datawrapper-import/pull/12 and tweaked it to account for the differences between prettier and scalafmt.

In particular, the hook is careful not to overwrite any unstaged changes: if a file has both staged and unstaged changes, running a formatter on it could (if something goes wrong) cause you to lose changes that git is unaware of, and they might be difficult to recover.

To Test

• Run the setup script, or manually run git config --local core.hooksPath scripts/git-hooks.
• Test the behaviour of the hook with combinations of:
  • typescript files with only staged changes which need formatting
  • typescript files with only unstaged changes which need formatting
  • typescript files with staged and unstaged changes, which need formatting
  • non-typescript files with staged or unstaged changes

[github-actions]

Deploy build 8576 of cms-fronts::facia-tool to CODE

All deployment options

• Deploy build 8576 of cms-fronts::facia-tool to CODE
• Deploy parts of build 8576 to CODE by previewing it first
• What's on CODE right now?

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From guardian/actions-riff-raff.

[fredex42]

😎 where did you get the script from originally?

[emdash-ie]

😎 where did you get the script from originally?

Nowhere, I wrote it! It was my first time using comm. I think I ran shellcheck on the script too? Will double-check.

[emdash-ie]

Ran shellcheck, no problems reported

[emdash-ie]

Ok, ran shellcheck with -oall and got some extra complaints about masked return values in pipelines (e.g. of git and comm) – not sure whether I want to fix those or not.

[prout-bot]

Seen on PROD (merged by @emdash-ie 6 minutes and 29 seconds ago) Please check your changes!