Feature => Pre-commit hook

[sc250024]

Enables this repository to serve as source for a helm-docs pre-commit hook compatible with the Pre-commit project. Alternatively, this could be its own repository; something like pre-commit-helm-docs.

Huge shoutout to @antonbabenko and the https://github.com/antonbabenko/pre-commit-terraform project, where I took most of the code from.

Description

In a nutshell, this enables someone using pre-commit to do something like the following in their Helm charts repository:

.pre-commit-config.yaml

- repo: https://github.com/norwoodj/helm-docs
  rev: master
  hooks:
    - id: helm_docs

If there are changes to their Helm chart (which are detected by helm-docs itself), this will automatically generate a corresponding README.md file. If the user hadn't updated and staged the README.md file before, this hook will fail, and ensure that a user always updates their README.md before they do a commit.

Motivation and Context

I was always doing this manually before:

$ cd stable/some-chart
$ helm-docs
$ git add README.md

Since I make extensive use of the Pre-Commit project, I wanted a hook to automatically generate the README.md for a chart I just changed.

How Has This Been Tested?

Tested locally. If you want to test a Helm chart repo against this hook, run the following in your Helm charts repo:

$ pwd
/a/local/copy/of/this/branch/helm-docs

$ cd /some/helm/chart/repo
$ vim stable/mychart/Chart.yaml # Do a quick version bump for testing
$ git add stable/mychart
$ pre-commit try-repo --all-files --verbose '/a/local/copy/of/this/branch/helm-docs' helm_docs

You should see that the hook will say "FAIL" because the README.md file changed, but it hasn't been staged yet. After staging, the pre-commit try-repo command will succeed.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[RothAndrew]

This would be fantastic! I use pre-commit a lot and this is a perfect fit for it.

[norwoodj]

Hey @sc250024 thanks a ton for the submission! I had a few comments, wasn't entirely clear why the whole getopt implementation was necessary for the script, but otherwise this is fantastic. If you can fix the couple comments up, I will merge this

[sc250024]

@norwoodj I updated based on the changes you requested.