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CONTRIBUTING.md

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+# Contributing
+
+The following is a set of guidelines for contributing to iterative_ensemble_smoother.
+
+## Commits
+
+We strive to keep a consistent and clean git history and all contributions
+should adhere to the following:
+
+1. All tests should pass on all commits(*)
+1. A commit should do one atomic change on the repository
+1. The commit message should be descriptive.
+
+We expect commit messages to follow the style described
+[here](https://chris.beams.io/posts/git-commit/). Also, focus on making clear
+the reasons why you made the change in the first place—the way things worked
+before the change (and what was wrong with that), the way they work now, and
+why you decided to solve it the way you did. A commit body is required for
+anything except very small changes.
+
+(*) Tip for making sure all tests passes, try out --exec while rebasing. You
+can then have all tests run per commit in a single command.
+
+## Pull Request Process
+
+1. Work on your own fork of the main repo
+1. Push your commits and make a draft pull request using the pull request template.
+1. Check that your pull request passes all tests.
+1. When all tests have passed and your are happy with your changes, change your
+   pull request to "ready for review" and ask for a code review.
+1. When your code has been approved—rebase, squash and merge your changes.