Elaborate on Git commit guidelines

[NVedsted]

The session plan does not elaborate on how a commit message should be constructed. This can be subjective so it makes sense to some extent, however, I would suggest at least adding some general guidelines.

E.g., some simple guidelines could look something like this:

1. Be consistent.
2. Spent the extra effort; you will thank yourself in the future.
3. Write in an imperative mood.
4. Describe the "why" and not the "what".
5. Leave out information that is already present in the commit. (File names, whether you created/updated, etc.)

Veronika Burduzhan also suggested on Slack to use Conventional Commits. While I personally believe it could be a bit overkill during the Git introduction, it could also be presented as an alternative.

@siderdk mentioned the following guidelines:

1. Keep them concise and descriptive
2. Learn about different conventions
3. Choose one style and stay consistent

These are also good, simple, and generally unopinionated.

[ElizabethSh]

I think adding examples will make it clearer. :)

[adamblanchard]

This is a great idea.

Some simple guidelines plus a few "good" example commit messages. I suggest we also add something like "When you push your commits and/or collaborate with others, your commit messages will be visible. They are also visible on your GitHub profile (in public repos).". In other words, don't write things like "omg plz just work now" or worse 😆.

I think specific conventions are overkill in this module, but we could introduce them in Collaboration with GitHub, a more advanced Git related module which appears in the specialism courses.