Merge branch '705-add-pre-commit-checks-to-the-repo' into 'master'

Resolve "Add pre-commit checks to the repo"

Closes #705

See merge request openappstack/openappstack!370

.pre-commit-config.yaml

@@ -9,6 +9,7 @@ repos:
       - id: detect-private-key
       - id: end-of-file-fixer
       - id: trailing-whitespace
+      - id: debug-statements
   - repo: https://github.com/jumanjihouse/pre-commit-hooks
     rev: 2.1.5
     hooks:
@@ -18,3 +19,13 @@ repos:
     rev: v1.23.0
     hooks:
       - id: hadolint
+  - repo: https://github.com/jazzband/pip-tools
+    # Makes sure the requirements.txt file is up to date
+    rev: 5.2.1
+    hooks:
+      - id: pip-compile
+  - repo: https://github.com/timothycrosley/isort
+    # Sorts import statements for you
+    rev: 5.0.9
+    hooks:
+      - id: isort

CONTRIBUTING.md

+# How to contribute
+
+## Preparing the development environment
+
+Make sure you have development dependencies installed in your development environment.
+
+```
+pip install -r requirements-dev.txt
+```
+
+## pre-commit hooks
+
+We use [pre-commit](https://pre-commit.com/) to maintain and install pre-commit
+hooks that should be executed before each commit.
+
+
+Please install these required tools on your system:
+
+* [hadolint](https://github.com/hadolint/hadolint) for linting the `Dockerfile`
+* [shellcheck](https://www.shellcheck.net/) and
+* [shfmt](https://github.com/mvdan/sh) to lint and validate shell scripts
+
+Then install pre-commit hooks:
+
+```
+pre-commit install
+```
+
+Running `git commmit` for the first time after installing the hook usually takes a
+little longer because `pre-commit` pulls it's hooks from upstream repositories.
+You can find all hooks in `.pre-commit-config.yaml`.
+
+In case you need to skip the execution of the pre-commit hooks (please don't!),
+use `git commit --no-verify`.
+
+
+## Adding dependencies
+
+Make sure you update our `requirements.txt` file before you push your changes.
+Whenever you need a new python package, add it to requirements.in and run
+
+`pip-compile`
+
+to generate an new `requirements.txt` which does not only pin the new package
+but also its dependencies.
+
+If the new package you are adding is only used by developers,
+please add it to the `requirements-dev.txt` file.

requirements-dev.txt

 # Add development requirements here
 # Please pin releases manually if necessary
 pip-tools
+pre-commit