Update to gitlab_git 10.4.1 and take advantage of preserved Ref objects

What does this MR do?

This is the fixed version of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5375, that got reverted because I missed some of the code that needed refactoring. I added specs and examples for all the code that failed on the last MR but wasn't covered by the existing specs.

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

Yes. The gitlab_git update changed the interface of the Gitlab::Git::Tag and Gitla::Git::Branch objects so that their target is a Gitlab::Git::Commit instead of a sha string. All the code that was expecting a sha string must be changed to account for this

Why was this MR needed?

The TagsController performance is suboptimal

What are the relevant issue numbers?

Closes #17073 (closed)

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 style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together

Marked the task CHANGELOG entry added as completed

Marked the task Added for this feature/bug as completed

Marked the task All builds are passing as completed

Marked the task Branch has no merge conflicts with master (if you do - rebase it please) as completed

Marked the task Branch has no merge conflicts with master (if you do - rebase it please) as incomplete

Marked the task Squashed related commits together as completed

Marked the task Conform by the style guides as completed

Added 225 commits:

• 250e1df7...17be364d - 224 commits from branch master
• 16c1371f - Update to gitlab_git 10.4.1 and take advantage of preserved Ref objects

Reassigned to @yorickpeterse

@eReGeBe There are some build failures that look legit.

Reassigned to @eReGeBe

Added ~18308 label

Added 9 commits:

• 16c1371f...b24ccd4a - 8 commits from branch master
• d00679d5 - Update to gitlab_git 10.4.1 and take advantage of preserved Ref objects

Added 1 commit:

• 08bac551 - Fix failing CommitController spec

@yorickpeterse the spec that was failing was spec/controllers/projects/commit_controller_spec.rb, because at app/helpers/commits_helper.rb:140 current_user.namespace was nil. This error did not occur on my local tests. I noticed that on the failing spec, there was a let(:user) { create(:user) } but also a before block with the following:

before do
   user = create(:user)

   sign_in(user)
end

That means that if in an example you would reference user it would not be the same as the signed in user. I suspect the problem arises from that. 08bac551 fixes that, and all specs now pass. However, I still don't know why this would fail specifically on this MR.

Reassigned to @yorickpeterse

@eReGeBe Ah, good to know. The build is green now so this is good to go.

Status changed to merged

mentioned in commit 5161983b

mentioned in merge request gitlab-com/www-gitlab-com!2910 (merged)