Add upvote/downvote fields to merge request and note API to preserve compatibility
As discussed in !1825 we should not break the API compatibility.
* This MR adds the fields `upvotes`/`downvotes` to the merge request API again, which always return `0`.
* Add the fields `upvote`/`downvote` to the notes API, which always return `false`
This behavior is documented in the API docs.
See merge request !1867
Add support for batch download operation
- Drops Accept for all download requests,
- Allows to do batch download for public projects and non-authorized users
- Returns 501 for legacy API with message to upgrade the client
/cc @marin @jacobvosmaer @yorickpeterse
See merge request !1842
Award Emoji
This it first iteration of award emoji feature.
We have plan to extend emoji picker by the next release.
For now, you can add award by clicking to the emoji picker or posting a regular comment with emoji like "👍" and any other. You can post not only emoji that listed in the emoji picker.
See merge request !1825
Deploy page should be shown for all pages not just root
Related to change already merged to Omnibus - gitlab-org/omnibus-gitlab!540
This change makes it so the deploy page is shown on all GitLab pages if the page exists. Users will no longer receive the 502 when deploys are happening.
See merge request !1828
Improve performance of user profiles, finding groups, and finding projects
This MR improves the following:
* Rendering of profile pages and Atom feeds
* Finding groups (using GroupsFinder & friends)
* Finding projects (using ProjectsFinder & friends)
Initially this MR was intended to only improve rendering of Atom feeds, but over time other fixes were introduced as well as the same code was the cause of all these problems.
See merge request !1790
Check which folders and archives should be packed before passing to tar command.
If user uses backup task with SKIP and skips one of the archives listed(uploads, builds, artifacts) backup create will give an error: `Cannot stat: No such file or directory`.
This MR fixes that by checking for skipped items.
Additionally, compact everything to avoid `TypeError: no implicit conversion of nil into String` errors.
See merge request !1824
This class can be used to join multiple AcitveRecord::Relation objects
together using a SQL UNION statement. ActiveRecord < 5.0 sadly doesn't
support UNION and existing Gems out there don't handle prepared
statements (e.g. they never incremented the variable bindings).
Expose builds feature
Expose builds feature in project settings (as feature).
Enable it by default for a new projects.
I deliberately named it builds instead of CI, because we actualy allow to run tests using infrastructure built-in GitLab. I'm free to change it.

If we are ok, I'll add feature tests for it.
/cc @sytses @dzaporozhets
See merge request !1767
Refactor complex methods
Make flog part of CI check which is not allowed to fail. I used high score (70) and refactored most complex method. In future releases we should lower acceptable score to something like 40..50
Part of #3444
See merge request !1794