Prevent links in PR description that link to redirect.redirect.github.com

[stefangr]

The different sections of the metadata go through the LinkAndMentionSanitizer twice.

Once per sub section and once as the complete message.

In case of source providers that support HTML that is not a problem. The Markdown is converted to HTML and after that left alone.

In case of a source provider that does not support HTML (like bitbucket) there is a problem.
The links in the markdown are converted from github.com to redirect.github.com. And in the second pass the links are converted from redirect.github.com to redirect.redirect.github.com.

This PR contains a fix so only the second pass will convert the links in case the source provider does not support HTML.

[jeffwidman]

What you're trying to do makes complete sense. 👍

Unfortunately, this solution is tracking state across function calls, and that can be hard to reason about and gets brittle quickly.

From a quick look at LinkAndMentionSanitizer, it looks like the github_redirection_service is the only URL that gets rewritten.

Would it be possible to instead modify the method that does the rewrite so that if the URL already matches the rewritten URL that it won't attempt another rewrite?

dependabot-core/common/lib/dependabot/pull_request_creator/message_builder/link_and_mention_sanitizer.rb

Lines 136 to 140 in 221a6e5

	def replace_github_host(text)
	text.gsub(
	/(www\.)?github.com/, github_redirection_service || "github.com"
	)
	end

That would be a bit more robust and keep all the "rewriting" logic constrained within that method.

[jeffwidman]

This looks so much more maintainable, thanks!