feat: add pre-commit to contributor docs

Author: jackhodgkiss

doc/source/contributor/index.rst

@@ -11,3 +11,4 @@ This guide is for contributors of the StackHPC Kayobe configuration project.
    release-notes
    environments/index
    package-updates
+   pre-commit

doc/source/contributor/pre-commit.rst

@@ -0,0 +1,38 @@
+================
+Pre-commit Hooks
+================
+
+StackHPC Kayobe configuration carries support for
+`pre-commit hooks <https://pre-commit.com/>`_ which simplify the use of git
+hooks enabling the identification and repairing of broken or poor code
+before committing.
+These hooks are designed to make working within SKC easier and less error prone.
+
+Currently the following hooks are provided:
+
+- ``check-yaml``: perform basic yaml syntax linting
+- ``end-of-file-fixer``: identify and automatically fix missing newline
+- ``trailing-whitespace``: identify and automatically fix excessive white space
+- ``ripsecrets``: identify and prevent secrets from being committed to the branch
+
+.. warning::
+   The hook ``ripsecrets`` is capable of preventing the accidental leaking of secrets
+   such as those found within `secrets.yml` or `passwords.yml`.
+   However if the secret is contained within a file on it's own and lacks a certain level
+   of entropy then the secret will not be identified as such as and maybe leaked as a result.
+
+Installation of `pre-commit` hooks is handled via the `install-pre-commit-hooks` playbook
+found within the Ansible directory.
+Either use `kayobe playbook run` or add the playbook as a hook within Kayobe config such as
+within `control-host-bootstrap/post.d`.
+Once done you should find `pre-commit` is available within the `kayobe` virtualenv.
+
+All that remains is the installation of the hooks themselves which can be accomplished either by
+running `pre-commit run` or using `git commit` when you have changes that need to be committed.
+This will trigger a brief installation process of the hooks which may take a few minutes.
+This a one time process and will not be required again unless new hooks are added or existing ones are updated.
+
+.. note::
+   Currently if you run ``pre-commit run --all-files`` it will make a series of changes to
+   release notes that lack new lines as well configuration files that ``check-yaml`` does not
+   approve of.