Update contribution guide for this repository

CONTRIBUTING.md

@@ -1,83 +1,36 @@
-# Contributing to this standard
+# Contributing
 
-🙇‍♀️ Thank you for contributing!
+Thank you for contributing to publiccode-validator-api. We welcome bug
+reports, questions, documentation improvements, and code changes.
 
-We – the maintainers and contributors of this project – understand that
-a standard like this can only be set in collaboration with as many public
-technologists, policy makers and interested folk as possible. Thus we
-appreciate your input, enjoy feedback and welcome improvements to this project
-and are very open to collaboration.
+## Issues
 
-We love issues and pull requests from everyone.
+Before opening an issue, please search the [existing
+issues](https://github.com/publiccodeyml/publiccode-validator-api/issues) to
+avoid duplicates. Use a new issue to report a reproducible problem, suggest an
+improvement, or ask a question about this repository.
 
-## Problems, suggestions and questions in Issues
+When reporting a problem, include the command you ran, the expected result,
+the actual result, and the version or commit you used when possible.
 
-Please help development by reporting problems, suggesting changes and asking
-questions. To do this, you can [create a GitHub
-Issue](https://help.github.com/articles/creating-an-issue/) for this project in
-the [GitHub Issues for
-  publiccode.yml Editor](https://github.com/italia/publiccode-editor/issues).
+## Pull requests
 
-You don't need to change any of our code or documentation to be a contributor!
+1. Fork the repository and create a branch from `main` for your change.
+2. Make the change and add or update tests and documentation where relevant.
+3. Run the test suite:
 
-## Documentation and code in Pull Requests
+   ```sh
+   go test -race ./...
+   ```
 
-If you want to add to the documentation or code of one of our projects you
-should make a Pull Request. 
+4. Open a pull request against
+   [`main`](https://github.com/publiccodeyml/publiccode-validator-api/tree/main).
+   Describe the problem it solves, the approach taken, and any related issue.
 
-If you never used GitHub, get up to speed with [Understanding the GitHub
-Flow](https://guides.github.com/introduction/flow/) or follow one of the great
-free interactive courses in the [GitHub learning lab](https://lab.github.com/)
-on working with GitHub and working with MarkDown, the syntax this project's
-documentation is in.
+Keep pull requests focused. Maintainers may ask for changes during review
+before merging a contribution.
 
-This project is [licenced AGPL-3.0-or-later](LICENSE.md), which means you are
-granted the freedoms to read, execute, change and redistributed the code with
-the same license. 
+## License
 
-### 1. Make your changes
-
-This project uses the [**GitFlow branching model** and
-workflow](http://nvie.com/posts/a-successful-git-branching-model/). When you've
-forked this repository, please make sure to create a feature branch following
-the GitFlow model.
-
-Add your changes in commits [with a message that explains
-them](https://robots.thoughtbot.com/5-useful-tips-for-a-better-commit-message).
-Document choices or decisions you make in the commit message, this will enable
-everyone to be informed of your choices in the future.
-
-If you are adding code, make sure you've added and updated the relevant
-documentation and tests before you submit your pull request. Make sure to write
-tests that show the behaviour of the newly added or changed code.
-
-### 2. Pull Request
-
-When submitting the pull request, please accompany it with a description of the
-problem you are trying to address and the issue numbers that this Pull Request
-fixes/addresses.
-
-### 3. Improve
-
-All contributions have to be reviewed by someone.
-
-It could be that your contribution can be merged immediately by a maintainer.
-However, usually, a new Pull Request needs some improvements before it can be
-merged. Other contributors (or helper robots) might have feedback. If this is
-the case the reviewing maintainer will help you improve your documentation and
-code.
-
-If your documentation and code have passed human review, it is merged.
-
-### 4. Celebrate
-
-Your ideas, documentation and code have become an integral part of this
-project. You are the Open Source hero we need! 
-
-In fact, feel free to open a PR to add your name to the [`AUTHORS`](AUTHORS.md)
-file and get eternal attribution.
-
----
-
-For more information on how to use and contribute to this project, please read
-the [`README`](README.md).
+By contributing, you agree that your work is licensed under the
+[AGPL-3.0-or-later](LICENSE).