Fix CHANGELOG for 8.12.6

[ci skip]

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
-v 8.13.0 (unreleased)
-  - Respond with 404 Not Found for non-existent tags (Linus Thiel)
-  - Truncate long labels with ellipsis in labels page
-  - Update runner version only when updating contacted_at
-  - Add link from system note to compare with previous version
-  - Use gitlab-shell v3.6.2 (GIT TRACE logging)
-  - Add `/projects/visible` API endpoint (Ben Boeckel)
-  - Fix centering of custom header logos (Ashley Dumaine)
-  - ExpireBuildArtifactsWorker query builds table without ordering enqueuing one job per build to cleanup
-  - Add an example for testing a phoenix application with Gitlab CI in the docs (Manthan Mallikarjun)
-  - Updating verbiage on git basics to be more intuitive
-  - Clarify documentation for Runners API (Gennady Trafimenkov)
-  - Change user & group landing page routing from /u/:username to /:username
-  - Prevent running GfmAutocomplete setup for each diff note !6569
-  - AbstractReferenceFilter caches project_refs on RequestStore when active
-  - Replaced the check sign to arrow in the show build view. !6501
-  - Add a /wip slash command to toggle the Work In Progress status of a merge request. !6259 (tbalthazar)
-  - Fix Error 500 when viewing old merge requests with bad diff data
-  - Speed-up group milestones show page
-  - Fix inconsistent options dropdown caret on mobile viewports (ClemMakesApps)
-  - Don't include archived projects when creating group milestones. !4940 (Jeroen Jacobs)
-  - Add tag shortcut from the Commit page. !6543
-  - Keep refs for each deployment
-  - Allow browsing branches that end with '.atom'
-  - Log LDAP lookup errors and don't swallow unrelated exceptions. !6103 (Markus Koller)
-  - Add more tests for calendar contribution (ClemMakesApps)
-  - Update Gitlab Shell to fix some problems with moving projects between storages
-  - Cache rendered markdown in the database, rather than Redis
-  - Avoid database queries on Banzai::ReferenceParser::BaseParser for nodes without references
-  - Simplify Mentionable concern instance methods
-  - Fix permission for setting an issue's due date
-  - API: Multi-file commit !6096 (mahcsig)
-  - Revert "Label list shows all issues (opened or closed) with that label"
-  - Expose expires_at field when sharing project on API
-  - Fix VueJS template tags being rendered in code comments
-  - Added copy file path button to merge request diff files
-  - Fix issue with page scrolling to top when closing or pinning sidebar (lukehowell)
-  - Add Issue Board API support (andrebsguedes)
-  - Allow the Koding integration to be configured through the API
-  - Add new issue button to each list on Issues Board
-  - Added soft wrap button to repository file/blob editor
-  - Update namespace validation to forbid reserved names (.git and .atom) (Will Starms)
-  - Add word-wrap to issue title on issue and milestone boards (ClemMakesApps)
-  - Fix todos page mobile viewport layout (ClemMakesApps)
-  - Fix inconsistent highlighting of already selected activity nav-links (ClemMakesApps)
-  - Remove redundant mixins (ClemMakesApps)
-  - Fix robots.txt disallowing access to groups starting with "s" (Matt Harrison)
-  - Close open merge request without source project (Katarzyna Kobierska Ula Budziszewska)
-  - Fix that manual jobs would no longer block jobs in the next stage. !6604
-  - Add configurable email subject suffix (Fu Xu)
-  - Added tooltip to fork count on project show page. (Justin DiPierro)
-  - Use a ConnectionPool for Rails.cache on Sidekiq servers
-  - Replace `alias_method_chain` with `Module#prepend`
-  - Enable GitLab Import/Export for non-admin users.
-  - Preserve label filters when sorting !6136 (Joseph Frazier)
-  - MergeRequest#new form load diff asynchronously
-  - Only update issuable labels if they have been changed
-  - Take filters in account in issuable counters. !6496
-  - Use custom Ruby images to test builds (registry.dev.gitlab.org/gitlab/gitlab-build-images:*)
-  - Prevent flash alert text from being obscured when container is fluid
-  - Append issue template to existing description !6149 (Joseph Frazier)
-  - Trending projects now only show public projects and the list of projects is cached for a day
-  - Memoize Gitlab Shell's secret token (!6599, Justin DiPierro)
-  - Revoke button in Applications Settings underlines on hover.
-  - Use higher size on Gitlab::Redis connection pool on Sidekiq servers
-  - Add missing values to linter !6276 (Katarzyna Kobierska Ula Budziszewska)
-  - Fix Long commit messages overflow viewport in file tree
-  - Revert avoid touching file system on Build#artifacts?
-  - Stop using a Redis lease when updating the project activity timestamp whenever a new event is created
-  - Add broadcast messages and alerts below sub-nav
-  - Better empty state for Groups view
-  - Update ruby-prof to 0.16.2. !6026 (Elan Ruusamäe)
-  - Replace bootstrap caret with fontawesome caret (ClemMakesApps)
-  - Fix unnecessary escaping of reserved HTML characters in milestone title. !6533
-  - Add organization field to user profile
-  - Fix enter key when navigating search site search dropdown. !6643 (Brennan Roberts)
-  - Fix deploy status responsiveness error !6633
-  - Make searching for commits case insensitive
-  - Fix resolved discussion display in side-by-side diff view !6575
-  - Optimize GitHub importing for speed and memory
-  - API: expose pipeline data in builds API (!6502, Guilherme Salazar)
-  - Notify the Merger about merge after successful build (Dimitris Karakasilis)
-  - Reorder issue and merge request titles to show IDs first. !6503 (Greg Laubenstein)
-  - Reduce queries needed to find users using their SSH keys when pushing commits
-  - Prevent rendering the link to all when the author has no access (Katarzyna Kobierska Ula Budziszewska)
-  - Fix broken repository 500 errors in project list
-  - Fix Pipeline list commit column width should be adjusted
-  - Close todos when accepting merge requests via the API !6486 (tonygambone)
-  - Ability to batch assign issues relating to a merge request to the author. !5725 (jamedjo)
-  - Changed Slack service user referencing from full name to username (Sebastian Poxhofer)
-  - Retouch environments list and deployments list
-  - Add multiple command support for all label related slash commands !6780 (barthc)
-  - Add Container Registry on/off status to Admin Area !6638 (the-undefined)
-  - Allow empty merge requests !6384 (Artem Sidorenko)
-  - Grouped pipeline dropdown is a scrollable container
-  - Cleanup Ci::ApplicationController. !6757 (Takuya Noguchi)
-  - Fix a typo in doc/api/labels.md
-  - API: all unknown routing will be handled with 404 Not Found
-  - Make guests unable to view MRs on private projects
-
 v 8.12.6
   - Update mailroom to 0.8.1 in Gemfile.lock  !6814