squashed - refactor to cope with sub sub N relations probably using the sub_relations method recursively.

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

[ci skip]

Advertise the PAT as an alternative unless GH import is not configured.
Signed-off-by: Rémy Coutable <remy@rymai.me>

When pushing commits to existing branches we don’t
need to flush branch git data (branch names / counts)

When flushes the cache when pushing commits skip to
flush branch and tag git data (names / counts) because
those operations are managed explicitly in each case

Repopulated expired cache as soon as possible

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

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

This allows us to control the trusted proxies while deployed in a private network. Normally Rack::Request will trust all private IPs as trusted proxies, which can caue problems if your users are connection on you network via private IP ranges.

Normally in a rails app this is handled by action_dispatch request, but rack_attack is specifically using the Rack::Request object instead.

[ci skip]

Only needed when the project view is ‘Files view’

We think this is valid because we’re just storing new data that always will be valid

The previous implementation would load the entire team member list and their
respective attributes. Now we only search for the user's specific
access level.

In gitlab-com/operations#42, this reduces the overall overhead of rendering
the issue from 28% to 20%.

First step of optimizing #19273

rebased with latest changes from master

Rebased to resolve merge conflicts

Requested in #14669

Added note to changelog

[ci skip]

In any case if just want the value which is always ‘gitlab’

require 'benchmark/ips'

Project.first # To load database things
GitlabIssueTrackerService.first # To load database things

Benchmark.ips do |x|
  x.config(:time => 5, :warmup => 2)

  x.report("current") do
    Project.new.default_issue_tracker.to_param
  end

  x.report("") do
    'gitlab'
  end

  x.compare!
end

Calculating -------------------------------------
             current     4.000  i/100ms
                        30.938k i/100ms
-------------------------------------------------
             current     47.298  (±10.6%) i/s -    232.000 
                          4.366M (±20.9%) i/s -     17.202M

Comparison:
                    :  4366456.0 i/s
             current:       47.3 i/s - 92318.26x slower

Depends on the changes in Workhorse (gitlab-org/gitlab-workhorse!48).