Support for custom deploy user (#54)

[lukasbach]

Adds the features requested in #54

Let me know if I should add or change anything. I'd be happy if the feature would be merged!

[lukasbach]

@enriikke let me know if I can do something to get this PR merged. I'm happy to change or add anything you're unhappy with with the current changeset!

[enriikke]

This is fantastic @lukasbach! Thank you so much for taking the time to write up a PR and my apologies for taking long to reply. ✨ ❤️

I added some suggestions to your PR and also there are a couple of things I would like to see to get it merged:

• Let's update the README to include the new inputs like we do for the existing inputs.
• It's a bit tricky to write tests for CLI tools like this one but it would be great to include a few to make sure we call git config ... with the right thing based not he inputs.

[lukasbach]

Hi @enriikke. Thanks for your suggestions, I've added them to the changeset. I've documented the inputs in the readme, added test cases for the arguments, removed the sha attribute from the commit message and formatted as you suggested. Feel free to let me know if there is something else I can do.

Also, I had issues using the nullish coalescing operator that you suggested (??), because the test case run in Github action complained that that's not valid Typescript. The project definitely uses a Typescript version that supports it, so I'm not sure if that's on jest-ts or something else maybe. Locally I did not get any error. Anyway, I've changed it to || because the variable can only either be a string or undefined anyways at this point.

[enriikke]

This is great! Thank you @lukasbach ✨

[lukasbach]

Cool, happy that I could help :)