Fixed GFM references not being included when update issue inline

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/2878

app/assets/javascripts/gfm_auto_complete.js

@@ -30,6 +30,7 @@ class GfmAutoComplete {
     this.input.each((i, input) => {
       const $input = $(input);
       $input.off('focus.setupAtWho').on('focus.setupAtWho', this.setupAtWho.bind(this, $input));
+      $input.on('change.atwho', () => input.dispatchEvent(new Event('input')));
       // This triggers at.js again
       // Needed for quick actions with suffixes (ex: /label ~)
       $input.on('inserted-commands.atwho', $input.trigger.bind($input, 'keyup'));

changelogs/unreleased/issue-description-gfm.yml

+---
+title: Fixed GFM references not being included when updating issues inline
+merge_request:
+author:

spec/features/issues/gfm_autocomplete_spec.rb

@@ -14,6 +14,18 @@ feature 'GFM autocomplete', feature: true, js: true do
     wait_for_requests
   end
 
+  it 'updates issue descripton with GFM reference' do
+    find('.issuable-edit').click
+
+    find('#issue-description').native.send_keys("@#{user.name[0...3]}")
+
+    find('.atwho-view .cur').trigger('click')
+
+    click_button 'Save changes'
+
+    expect(find('.description')).to have_content(user.to_reference)
+  end
+
   it 'opens autocomplete menu when field starts with text' do
     page.within '.timeline-content-form' do
       find('#note_note').native.send_keys('')