Preserve gem path so that we use the same gems

See merge request gitlab-org/gitlab-ce!15986

Tidy up the documentation of Gitlab HA/Gitlab Application

See merge request gitlab-org/gitlab-ce!16011

Make sure two except won't overwrite each other

See merge request gitlab-org/gitlab-ce!16010

This is a pretty boring solution, but I can't
think of a good idea right now and this might be
good enough for now...

Without this patch, I would end up with:

```
An error occurred in a `before(:suite)` hook.
Failure/Error: raise "could not connect to gitaly at #{socket.inspect} after #{sleep_time} seconds"

RuntimeError:
  could not connect to gitaly at "tmp/tests/gitaly/gitaly.socket" after 10 seconds
```

Digging into it, it's because `scripts/gitaly-test-spawn` could not
spawn the process, because it cannot find the installed gems.

I personally installed all my gems under $HOME, namely with:

* `gem install rake --user-install` or:
* `bundle install --path ~/.gem`

The gems would be installed to `~/.gem/ruby/2.4.0/gems`, where
the version is Ruby ABI version.

Now we're changing $HOME, making RubyGems think that the gems
would be installed to `tmp/tests/ruby/2.4.0/gems` which is
apparently not the case.

In order to workaround this, we could preserve $GEM_PATH
populated by RubyGems, ignoring the default path based on $HOME.

Fix cluster enviroment missing

See merge request gitlab-org/gitlab-ce!15973

Resolve "Codequality and qa:internal is leaking to Shared Runners"

Closes #41139

See merge request gitlab-org/gitlab-ce!15957

Fix missing WHERE clause in 20171106135924_issues_milestone_id_foreign_key migration

Closes gitlab-com/infrastructure#3416

See merge request gitlab-org/gitlab-ce!15997

If milestone_id is NULL, we shouldn't need to update it to be NULL again. This
was causing us to touch almost all rows in the issues table for no good
reason.

Closes https://gitlab.com/gitlab-com/infrastructure/issues/3416

fix the commit diff discussion sending the wrong url

See merge request gitlab-org/gitlab-ce!15988

Use queue_namespace rather than enqueue_in

See merge request gitlab-org/gitlab-ce!15989

Export and use Notes ES module

See merge request gitlab-org/gitlab-ce!15953

Signed-off-by: Rémy Coutable <remy@rymai.me>

Only render signout screen when user is signed out

Closes #41117 and #39843

See merge request gitlab-org/gitlab-ce!15935

it should now send you to the merge request diff path scoped to the commit.

Resolve "Todo notification count shows notification without having a todo"

Closes #40871

See merge request gitlab-org/gitlab-ce!15807

List of avatars should never show +1

Closes #39298

See merge request gitlab-org/gitlab-ce!15972

Add button to run scheduled pipeline immediately

Closes #38741

See merge request gitlab-org/gitlab-ce!15700

Resolve "Document how LFS integrity check push prevention works"

Closes #39836

See merge request gitlab-org/gitlab-ce!15958

When the target is deleted, todos are destroyed, but we did not reset the todo
cache for users with todos on the deleted target. This would only update after
the next time the todo cache was updated for that user.

Stop sending milestone and labels for Projects::MergeRequestsController#show.json requests

See merge request gitlab-org/gitlab-ce!15847

Translate contributors page dates

Closes #39283 and #38592

See merge request gitlab-org/gitlab-ce!15846

Fixes 40842 - Adds extra cookies to JIRA service requests

Closes #40842

See merge request gitlab-org/gitlab-ce!15956

The list of avatars should never show +1. If you have +1, that means you can use that space to show that person's avatar,
for that reason should always start with +2.

# Conflicts:
#   app/assets/javascripts/main.js

Optimize QA pipeline and don't run irrelevant jobs

Closes gitlab-qa#140

See merge request gitlab-org/gitlab-ce!15977