Fix bug where manually merged branches in a MR would end up with an empty diff

This bug manifested in 8.1 with the refactoring of `RefreshService`. Here's what happens:

1. User create a new branch `foo`.
2. User creates a merge request for `foo`.
3. User merges `foo` into `master` by hand.
4. `RefreshService` reloads the merge request. Since `master` is equivalent to `foo`, this results in an empty diff.
5. `RefreshService` then closes the MR.

This wasn't an issue when you use the normal "Accept Merge Request" flow because the act of clicking the button closes the merge request, so step 4 never happens.

Closes #3314

See merge request !1758

Only redirect to homepage url when its not the root url

It was possible to create an infi redirect when the user set up the
`home_page_url` to redirect to the main URL of the gitlab instance.

This fix makes sure this redirect is not possible.

Fixes #1020 

/cc @dblessing 

See merge request !1703

Add Facebook authentication

See merge request !1740

[ci skip]

Spread out runner contacted_at updates

This is meant to prevent having too many concurrent UPDATE requests
caused by runners checking in.

See merge request !1722

Force update refs/merge-requests/X/head upon a push to the source branch of a merge request

If a user rebases and does a force push, GitLab would not update the `refs/merge-requests/X/head` link. Using the -f flag forces this to happen.

Closes #3138

See merge request !1683

[ci skip]

Add projects path index

Fixes performance regression introduced by !1649

See merge request !1692

Fix CI badge

The previous code relied on having on ref stored in commit, however the ref was moved to the build.

Fixes #3104

See merge request !1690

[ci skip]

Fix visibility of specific runners

See merge request !1688

[ci skip]

Add migration to remove the contents of the satellites dir

See merge request !1681

Fix regex in redis version check

[ci skip]

Fix cloning Wiki repositories via HTTP

Cloning a project Wiki over HTTP would end up cloning the main repository
since the .wiki extension was being stripped.

Closes #3106

See merge request !1676

Fix edit readme link on project home page

See merge request !1668

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Prefer project with exact path to differently cased one when both exist.

Fixes #3113.

See merge request !1649

Fix 500 when editing CI services

Fixes #3090

See merge request !1663

Require jobs to be named

This properly presents error for .gitlab-ci.yml having empty job name.

See merge request !1662

Fix CSS class for runner status

Fixes #3117 

See merge request !1665

[ci skip]

Don't show "Add README" link in an empty repository if user doesn't have access to push

Reporter users would see this before even though they didn't have access to push:

![image](/uploads/1dd328ab7e58cd00c5b696f079816e16/image.png)

It's not complete accurate to include the push command-line instructions, but users may still want the instructions to clone. After:

![image](/uploads/3d214e140916d2f174d0b5fec0ac472d/image.png)

Closes #3094

See merge request !1626

Make sure MR refresh service correctly determines newly added commits.

Fixes #3140.

See merge request !1659

Fix build trace updating

Fixes #2910 

See merge request !1657

Remove CI migration

See merge request !1656