(CAT-1878) Write README

README.md

@@ -1 +1,30 @@
-# puppet-lint-check_unsafe_interpolations
+# puppet-lint: check unsafe interpolations plugin
+
+This repository contains a custom check for puppet-lint, used to identify unsafe interpolations within Puppet manifests, specifically within `exec` resource blocks. The check focuses on ensuring that dynamic expressions, particularly those that could introduce security vulnerabilities, are flagged and reviewed.
+
+## How It Works
+
+1. **Exec Resource Gathering**: Collects all `exec` resources from the Puppet manifest for further analysis.
+2. **Title Safety Check**: Iterates over titles of `exec` resources, checking for variables that might be interpolated unsafely.
+3. **Parameter Inspection**: Examines the `command`, `onlyif`, and `unless` parameters of each `exec` resource, looking for patterns that suggest unsafe interpolations.
+
+## Warning
+
+This plugin is designed to flag potentially unsafe interpolations within `exec` resource blocks in Puppet manifests. However, in its current state, when it identifies a problem, it may inadvertently cause your CI/CD pipelines to fail. If you use this plugin, it is recommended to review and address flagged issues promptly. Use this plugin under your own risk!
+
+It is also possible to prevent pipeline failures by explicitly disabling `PuppetLint.configuration.fail_on_warnings` in your Lint configuration file. However, keep in mind that this will disable failures
+for all Lint checks and could potentially result in Lint issues being overlooked in the long run.
+
+## Usage
+
+To implement this check, simply add the following line in your Gemfile and run `bundle install`:
+
+```ruby
+gem 'puppet-lint-check_unsafe_interpolations'
+```
+
+## Development
+
+If you run into an issue with this tool or would like to request a feature you can [raise a PR](https://github.com/puppetlabs/puppet-lint-check_unsafe_interpolations/pulls) with your suggested changes. Alternatively, you can [raise a Github issue](https://github.com/puppetlabs/puppet-lint-check_unsafe_interpolations/issues) with a feature request or to report any bugs.
+Every other Tuesday the DevX team holds [office hours](https://puppet.com/community/office-hours) in the [Puppet Community Slack](http://slack.puppet.com/), where you can ask questions about this and any other supported tools.
+This session runs at 15:00 (GMT) for about an hour.