Delete leftover code for referenced_merge_requests

We rewrote Related MRs widget using Vue.
The previous implementation was using Haml templates
and calling referenced_merge_requests endpoint which is
now deprecated. This MR deletes leftover stuff them.

app/controllers/projects/issues_controller.rb

@@ -132,18 +132,6 @@ class Projects::IssuesController < Projects::ApplicationController
     render_conflict_response
   end
 
-  def referenced_merge_requests
-    @merge_requests, @closed_by_merge_requests = ::Issues::ReferencedMergeRequestsService.new(project, current_user).execute(issue)
-
-    respond_to do |format|
-      format.json do
-        render json: {
-          html: view_to_html_string('projects/issues/_merge_requests')
-        }
-      end
-    end
-  end
-
   def related_branches
     @related_branches = Issues::RelatedBranchesService.new(project, current_user).execute(issue)
 

app/views/projects/issues/_merge_requests_status.html.haml

-- time_format = '%b %e, %Y %l:%M%P %Z%z'
-
-- if merge_request.merged?
-  - mr_status_date = merge_request.merged_at
-  - mr_status_title = _('Merged')
-  - mr_status_icon = 'merge'
-  - mr_status_class = 'merged'
-- elsif merge_request.closed?
-  - mr_status_date = merge_request.closed_event&.created_at
-  - mr_status_title = _('Closed')
-  - mr_status_icon = 'issue-close'
-  - mr_status_class = 'closed'
-- else
-  - mr_status_date = merge_request.created_at
-  - mr_status_title = mr_status_date ? _('Opened') : _('Open')
-  - mr_status_icon = 'issue-open-m'
-  - mr_status_class = 'open'
-
-- if mr_status_date
-  - mr_status_tooltip = "<div><span class=\"bold\">#{mr_status_title}</span> #{time_ago_in_words(mr_status_date)} ago</div><span class=\"text-tertiary\">#{l(mr_status_date.to_time, format: time_format)}</span>"
-- else
-  - mr_status_tooltip = "<div><span class=\"bold\">#{mr_status_title}</span></div>"
-
-%span.mr-status-wrapper.suggestion-help-hover{ class: css_class, data: { toggle: 'tooltip', placement: 'bottom', html: 'true', title: mr_status_tooltip } }
-  = sprite_icon(mr_status_icon, size: 16, css_class: "merge-request-status #{mr_status_class}")

config/routes/project.rb

@@ -360,7 +360,6 @@ constraints(::Constraints::ProjectUrlConstrainer.new) do
           post :toggle_subscription
           post :mark_as_spam
           post :move
-          get :referenced_merge_requests
           get :related_branches
           get :can_create_branch
           get :realtime_changes

spec/javascripts/issue_spec.js

@@ -113,7 +113,6 @@ describe('Issue', function() {
         mock = new MockAdapter(axios);
 
         mock.onGet(/(.*)\/related_branches$/).reply(200, {});
-        mock.onGet(/(.*)\/referenced_merge_requests$/).reply(200, {});
 
         findElements(isIssueInitiallyOpen);
         this.issue = new Issue();

spec/views/projects/issues/_merge_requests_status.html.haml_spec.rb

-# frozen_string_literal: true
-require 'spec_helper'
-
-describe 'projects/issues/_merge_requests_status.html.haml' do
-  around do |ex|
-    Timecop.freeze(Date.new(2018, 7, 22)) do
-      ex.run
-    end
-  end
-
-  it 'shows date of status change in tooltip' do
-    merge_request = create(:merge_request, created_at: 1.month.ago)
-
-    render partial: 'projects/issues/merge_requests_status',
-           locals: { merge_request: merge_request, css_class: '' }
-
-    expect(rendered).to match("Opened.*about 1 month ago")
-  end
-
-  it 'shows only status in tooltip if date is not set' do
-    merge_request = create(:merge_request, state: :closed)
-
-    render partial: 'projects/issues/merge_requests_status',
-           locals: { merge_request: merge_request, css_class: '' }
-
-    expect(rendered).to match("Closed")
-  end
-end