Add pre-commit for automatically updating date stamps

[jwallwork23]

Add pre-commit for automatically updating date stamps

Closes #658.

Works for me but worth please check this works for you too.

[einola]

It kind of works:

1. You need GNU sed. BSD sed doesn't work.
2. It modifies your files but just commits the parts I've already git add-ed.

I don't know if we want to make a fuss about 1. Can this be done with plain BSD sed?

The behaviour in 2 can be considered a feature. What I added is committed, nothing more. But the hook kindly suggests how I should modify my files so I can review them and then add them. I guess this is normal behaviour, but it was unexpected to me, not having used pre-commit hooks before.

[jwallwork23]

Can you check if using /bin/bash instead of /usr/bin/bash works on linux? Other than that, it's good.

Ah yes, I always forget about this. Works fine on Linux yeah. Thanks!

[jwallwork23]

@einola did the spaces come out okay for you? I had to add a few extra spaces to get things to align nicely. I'm currently using

#!/bin/bash

# An example pre-commit file for nextSIM-DG development

for FILE in $(git diff --cached --name-only | grep -iE '\.(cpp|cc|h|hpp)$'); do
  # Apply clang-format for linting
  clang-format -i ${FILE} --verbose
  # Update date stamp to today's date
  sed -i "s/$(grep '\* @date' ${FILE})/ @date    $(date '+%d %b %Y')/" ${FILE}
done

[einola]

I didn't check the alignment :) ... but feel free to change it before merging.

[jwallwork23]

Okay I think the latest commit should preserve spaces. Do the additional commands work on Mac, too?