borked upgrade: broken UI, not on any branch

I had a functioning 7.13.5 EE running on the sameersbn/gitlab:7.13.5 image. I started out on the 7.13.1ce image and wound up on 7.13.5 as I upgraded to EE.

Decided it was time to upgrade from 7.13.5 to the latest version (8.3). I now have a broken UI; my guess is that is likely due to my faulty upgrade method. Gitlab is working through the command line, though the UI is not happy. For a couple of examples: the landing page shows no activity, yet it does show all of the relevant repository names over on the right (though I get a consistent 500 error if I click on any of them). I can see the user accounts, and our ssh keys, but I don't see any tooling to add an ssh key.

In retrospect, I am guessing that the issue comes from unwittingly upgrading an EE version to a CE version (oops, ouch). Though, I am also wondering if somehow the database got chewed on.

If I spin up a new container via docker run..., right off the bat I have a disturbing git status:

root@foo:/home/git/gitlab# git status
Not currently on any branch.
Changes not staged for commit:
  (use "git add/rm <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

    modified:   app/controllers/application_controller.rb
    modified:   db/schema.rb
    deleted:    log/.gitkeep
    deleted:    public/uploads/.gitkeep

Untracked files:
  (use "git add <file>..." to include in what will be committed)

    log
    public/assets
    public/uploads

no changes added to commit (use "git add" and/or "git commit -a")

You may have guessed this, but just to be clear:

root@foo:/home/git/gitlab# ls -alp .git/refs/heads/
total 8
drwxr-xr-x 2 git git 4096 Jan  5 02:30 ./
drwxr-xr-x 5 git git 4096 Jan  5 02:30 ../

So questions:

1. Is there any info anyone can think of that I can provide to make this ticket more clear?
2. Is there anything anyone can think of that I can do to get me pointed at master?
3. Is there anything anyone can think of that I should remove/update in my linked storage volume that would get the UI back on track?
4. Any thoughts/advice on the possibility of database issue?
5. Anything anyone can think of to save me from doing a fresh install?

Start by reproducing the reported 7.13.5-to-8.3 container upgrade and inspect the repository state, including .git/refs/heads/, app/controllers/application_controller.rb, and db/schema.rb. Compare the linked storage volume and command-line behavior with the broken UI; the issue does not define a clear fix or acceptance criteria beyond restoring a working UI without a fresh install.