fix: Only highlight Terraform changes on GitHub

[pauloconnor]

The lazy regex for converting Terraform diffs to GitHub diffs would also mark YAML and other plain text that happen to start with -, +, or ~. This is a bit more selective, scanning for obvious Terraform changes that contain ->, << for heredocs, { for modules/resources/blocks, known after apply, and [ for lists. It will also do a second pass to attempt to capture changes to lists too.

Closes #2241

[dupuy26]

This is great, thanks! The tests and regexes look correct to me. It might be worth adding a test with embedded <<EOT YAML content with list items, to ensure that future changes don't break things (e.g. by removing the trailing comma for the list check).

I'd approve this anyhow, except that I think my approval won't count for anything.

[pauloconnor]

Adding a test with embedded <<EOT YAML content with list items, to ensure that future changes don't break things (e.g. by removing the trailing comma for the list check).

Do you have a sample of what mean? I don't quite follow

[dupuy26]

Do you have a sample of what mean? I don't quite follow

Looking at line 2203 of markdown_renderer_test.go I think you already have this covered (there's also a base64 block example). I think it is absolutely fine to go.

[jamengual]

@pauloconnor Thanks for the contribution