Workhorse to serve email diffs

See merge request !4590

Show basic system info on admin panel. Closes #18886

![Screen_Shot_2016-06-23_at_10.57.07_AM](/uploads/df33bc3dc36ceaf86f5e479ca15b83f3/Screen_Shot_2016-06-23_at_10.57.07_AM.png)

See merge request !4858

Fix group visibility form layout in application settings

## What does this MR do?

This fixes UI consistency related to setting group visibility levels in application settings. See screenshots.

## Screenshots (if relevant)

#### Before

![visiblity_consistency](/uploads/9cf9b517e25cd661ac61bdd7ca2d82f4/visiblity_consistency.png)

#### After

![group_visibility_after](/uploads/7b317684d047716f2aa5e60d19a4281b/group_visibility_after.png)

See merge request !4848

Closes #18949

Fixed dropdown not filtering queries entered before data is loaded

## What does this MR do?

Triggers a 'keyup' event on a filters input to force it to process any text that was added before the data was retrieved and rendered.

## Are there points in the code the reviewer needs to double check?

😕 

## Why was this MR needed?

UX

## What are the relevant issue numbers?

Closes #18942.

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4846

[ci skip]

Fix CHANGELOG

Fixes double header for 8.9.3 entries

See merge request !4971

Find all builds for commit if there are multiple pipelines for it

## What does this MR do?

This MR fixes a builds API. When multiple pipelines were triggered for a commit, then API returned builds only from the last pipeline.

## What are the relevant issue numbers?

Closes #18912  
Closes #19243 

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] API support added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4849

Use clock_gettime for all performance timestamps

This MR adjusts the performance monitoring code to use `Process.clock_gettime` (thus `clock_gettime(3)`) instead of `Time.now`.

Using `Time.now` / `Time.new` adds more overhead than `Process.clock_gettime`, it also doesn't provide a way of getting timestamps in nanoseconds (which `Process.clock_gettime` does allow).

See merge request !4899

Implement UI for new project page

## What does this MR do?

Updates the project creation page to conform with the latest UI updates.

## Are there points in the code the reviewer needs to double check?

Ney.

## Why was this MR needed?

Updated UI.

## What are the relevant issue numbers?

Closes #2542.

## Screenshots (if relevant)

**Desktop:**

![Screen_Shot_2016-06-18_at_04.00.48](/uploads/0313eee96a2aef9ed5e048989548b133/Screen_Shot_2016-06-18_at_04.00.48.png)

**Mobile:**

![Screen_Shot_2016-06-18_at_04.01.00](/uploads/505b110c3fcbf523aac08797db9f6781/Screen_Shot_2016-06-18_at_04.01.00.png)

See merge request !4766

Process.clock_gettime allows getting the real time in nanoseconds as
well as allowing one to get a monotonic timestamp. This offers greater
accuracy without the overhead of having to allocate a Time instance. In
general using Time.now/Time.new is about 2x slower than using
Process.clock_gettime(). For example:

    require 'benchmark/ips'

    Benchmark.ips do |bench|
      bench.report 'Time.now' do
        Time.now.to_f
      end

      bench.report 'clock_gettime' do
        Process.clock_gettime(Process::CLOCK_MONOTONIC, :millisecond)
      end

      bench.compare!
    end

Running this benchmark gives:

    Calculating -------------------------------------
                Time.now   108.052k i/100ms
           clock_gettime   125.984k i/100ms
    -------------------------------------------------
                Time.now      2.343M (± 7.1%) i/s -     11.670M
           clock_gettime      4.979M (± 0.8%) i/s -     24.945M

    Comparison:
           clock_gettime:  4979393.8 i/s
                Time.now:  2342986.8 i/s - 2.13x slower

Another benefit of using Process.clock_gettime() is that we can simplify
the code a bit since it can give timestamps in nanoseconds out of the
box.

Unused gon variable with very bad performance

## What does this MR do?

Remove an unused variable with a lot of performance penalty. It was opening a transaction just to return a constant string.

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added

See merge request !4969

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

docs: fix default_branch_protection default



See merge request !4479

Switched mobile button icons to ellipsis and angle

## What does this MR do?
Switches the mobile button icons

## What are the relevant issue numbers?
Closes #19170   
Part of #19200 

## Screenshots (if relevant)
![Screen_Shot_2016-06-27_at_9.08.28_AM](/uploads/7784489402e342e671d02b24d2ea0d64/Screen_Shot_2016-06-27_at_9.08.28_AM.png)


See merge request !4944

Resolve "Pin should show up at 1280px min"

## What does this MR do?
Decreased window min width for pinned sidebar

## What are the relevant issue numbers?
Closes  #19171    
Part of #19200 

## Screenshots (if relevant)
![Screen_Shot_2016-06-27_at_9.36.13_AM](/uploads/d0a87bca5af1bee808c5b1046c0ecf72/Screen_Shot_2016-06-27_at_9.36.13_AM.png)

See merge request !4947

Use GIT_DEPTH for builds

## What does this MR do?
Enables experimental feature to use shallow cloning. 

## Why was this MR needed?
To speed up the builds and reduce the pressure on NFS servers. This should save us between 30s to 1m of the time of each build.

## More information
 `GIT_DEPTH`: https://gitlab.com/gitlab-org/gitlab-ci-multi-runner/merge_requests/188

## Problems
- Too small value for `GIT_DEPTH` can make it impossible to retry old changes.
You will see `unresolved reference` in build log.
We should then reconsider changing `GIT_DEPTH` to higher value
- Mechanism that rely on `git describe` may not work correctly when `GIT_DEPTH` is set. This will happen, because only part of the git history is present on the build machine

## Requirements
GitLab Runner 1.3.0. Currently all our internal runners use beta release or 1.3.0 with support for `GIT_DEPTH`.

@pcarranza Please decide when to merge that. We should start monitoring to see an impact on our NFS servers.

cc @jacobvosmaer-gitlab @pcarranza 


See merge request !4730

Add SMTP upgrade information

8.8 to 8.9 requires an update to the SMTP settings for source installs.

See merge request !4966

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

Closes #19252

[ci skip]

Refactor GitLab architecture document

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/14236

See merge request !3694

Display last commit of deleted branch in push events

## What does this MR do?

Display the last commit of a deleted branch in the push events of a project.

## Are there points in the code the reviewer needs to double check?

Is the change in `app/models/event.rb` the correct way to display a two-line event for deleted branches?

## Why was this MR needed?

It is easier to restore an accidentally deleted branch if the commit hash is displayed in the push events.

## What are the relevant issue numbers?

Fixes #18659

## Screenshots

### Before garbage collection

![before-gc](/uploads/5674cd53e1564d48b7f2f8406ea0fbed/before-gc.png)

### After garbage collection

![after-gc](/uploads/80950c1932feeb3b69d0fc11b8f7acf4/after-gc.png)

See merge request !4699

1. Return 404 if commit is not found (RESTful resource not found)
2. Return an empty array if pipeline is not found (resource present, no
   associated builds found)
3. Return an empty array if pipeline found but no builds there (resource
   present, no associated builds)