[WIP] Convert GFM reference handling to html-pipeline filters

• Issue references (including cross-project)
  • Specs
• External issue tracker references
  • Specs
• Merge Request references (including cross-project)
  • Specs
• Users/Groups
  • Specs
• Snippets (including cross-project)
  • Specs
• Commits (including cross-project)
  • Specs
• Commit ranges (including cross-project)
  • Specs
• Labels
  • Specs
• Fix ReferenceExtractor
• Fix Mentionable

Separate merge request:

• Task lists (probably replace with the task_list gem)

Feedback needed

• The old GFM specs test snippet references as being cross-referable, but the GFM docs don't mention this. Are they/should they be?
• Are commit ranges cross-referable? Again the docs don't define this behavior, but this time neither do the specs.
• As far as I can tell, external issue refs such as JIRA-123 are linked without checking if the ID is valid or not (not even sure if there is a way to check). Is that the correct behavior?

mentioned in issue #1379 (closed)

WIP: https://gitlab.com/tsigo-gitlab/gitlab-ce/compare/master...rs-reference-filters

I'll squash it down, of course.

That's awesome. Do you plan to move the new filters to the filter gem after finishing development?

I don't think it's feasible/worthwhile because of how tightly coupled the filters are to things like GitLab's models and routes.

Yeah, that was something I was thinking about too. @DouweM Since the filters from gitlab-html-pipeline gem are also very close to GitLab, I think moving them to the GitLab codebase would make sense. Do you agree?

@razer6 Agreed, but move the existing ones in a separate MR, please.

@razer6 I'll handle that when I'm done with this one, then.

The old GFM specs test snippet references as being cross-referable, but the GFM docs don't mention this. Are they/should they be?

Are commit ranges cross-referable? Again the docs don't define this behavior, but this time neither do the specs.

Let's make everything that's scoped to a project cross-referable, so that goes for snippets and commit ranges as well.

As far as I can tell, external issue refs such as JIRA-123 are linked without checking if the ID is valid or not (not even sure if there is a way to check). Is that the correct behavior?

Yep, validation of external issues is close to impossible.

Squashed down after more progress on this. All specs passed locally.

Couple things:

• I'm not happy with the format of all the result hashes. Some stuff returns the actual model, others return an Integer- or String-based ID. Need to hammer that out a bit more.
• ReferenceExtractor is basically a giant hack at the moment and duplicates a lot of what the filters were meant to replace.
• Mentionable could use some work but I spent almost all day navigating its maze of a shared example-based specs and I'm kind of afraid to touch them now.

@rspeicher Feel free to create a WIP merge request, where we can discuss the code a bit easier.

@DouweM Done, on dev.

Status changed to closed