Add GFM support to nested groups

What does this MR do?

• Use new regex for user reference parsing that supports / in path
• Allows mention of nested groups in gfm like @gitlab/subgroup

Are there points in the code the reviewer needs to double check?

no

Why was this MR needed?

So you can mention nested group in gfm like @gitlab/subgroup

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/2772

mentioned in issue #2772 (closed)

added 1 commit

• 8f620a0e - Add GFM support to nested groups

Compare with previous version

mentioned in merge request !9136 (closed)

@grzesiek please review.

I made a concept at https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/9136 that extracts group into separate gfm filter in case we want this after 9.0.

assigned to @grzesiek

@dzaporozhets I left just a two questions! It looks good to me. Let's pass this MR to @rspeicher who is an endboss is also a GitLab Flavored Markdown expert.

assigned to @rspeicher

resolved all discussions

@rspeicher please review and assign back to me.

assigned to @dzaporozhets

resolved all discussions

added 1 commit

• 57bb6b1a - Add GFM support to nested groups

Compare with previous version

enabled an automatic merge when the pipeline for 57bb6b1a succeeds

added 210 commits

• 57bb6b1a...e5f446b7 - 209 commits from branch master
• 2c55fd00 - Add GFM support to nested groups

Compare with previous version

enabled an automatic merge when the pipeline for 2c55fd00 succeeds

merged

added subgroups label

@dzaporozhets I don't know if this is GFM in general, but the autocomplete doesn't work when you add /.

If for example there is a group gitlab/software and another gitlab-org/software and you want to only see those form the gitlab group, when you write @gitlab/ the autocomplete stops working.

@axil thanks, please create an issue.

You're right https://gitlab.com/gitlab-org/gitlab-ce/issues/29323