Fix referals for :back and relative URL installs.

`app/views/layouts/_head.html.haml` currently sets the referrer policy to "origin". This disables the use of `{ redirect_to :back }`, which is used frequently throughout GitLab, and also breaks relative URL installs for browsers that obey this policy (e.g., Chrome).

For example, using the "origin" policy the "Save Changes" button on the profile screen will (a) dump you at the GitLab home screen (which I can confirm on GitLab.com) or (b) dump you out of GitLab entirely for a relative URL install (which I can confirm on my local install).

The right policy is "origin-when-cross-origin", which disables HTTP_REFERER when coming from other sites but enables it internally. (https://w3c.github.io/webappsec-referrer-policy/) I can confirm that this fixes the problems with ":back" on my install.

See merge request !1505

Document known issue with Reply by email and multiple application servers.

See merge request !1499

Revert "Merge branch 'projects' into 'master'"

This reverts commit 2b493695, reversing
changes made to b5c12f74.

This reverts !1487 MR because it cause bugs on mobile devices 


cc @skyruler 

See merge request !1509

This ensures that blocks defines using "benchmark_subject" have access
to methods defined using let/subject & friends.

Basic RSpec/benchmark-ips powered benchmark suite

Corresponding issue: #2909, see the commit messages for more details.

A few things to note:

1. The current use of `subject` isn't exactly easy on the eyes due to them having to return a Proc, I'm not sure yet how (and if) we can work around this.
2. The maximum amount of iterations in the current `User.by_login` benchmark is arbitrary, we might have to adjust it once said method's performance has been improved.
3. Benchmarks currently take 2 seconds to warm up and 5 seconds to run (benchmark-ips defaults). 
4. The custom RSpec matcher file (`benchmark_matchers.rb`) is a bit messy, any feedback on this would be appreciated

Any comments/feedback on this would be greatly appreciated.

See merge request !1503

Fix anchors to comments in diffs

https://gitlab.com/gitlab-org/gitlab-ce/issues/2218

See merge request !1508

Golang download instructions assume amd64



See merge request !1488

This reverts commit 2b493695, reversing
changes made to b5c12f74.

This will be disallowed again once the existing benchmarks pass (which
relies on #2341).

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

This class method can be used in "describe" blocks to specify the
subject of a benchmark. This lets you write:

    benchmark_subject { Foo }

instead of:

    benchmark_subject { -> { Foo } }

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

change build status image to svg

Fix "useless assignment" Rubocop warnings

Fix bug where transferring a project would result in stale commit links

Transferring a project to another namespace updates the project's updated_at
field, but since the cache key did not depend on the object, the page fragments
were not invalidated. This resulted in stale links to the commits. Changing
the cache key to use the project pathname solves this issue.

Closes gitlab-org/omnibus-gitlab#843

See merge request !1497

Improve project page height

old thing. Grey block not aligned to the bottom. It was a scroll even with short project description.

![Screen_Shot_2015-10-01_at_16.03.24](https://gitlab.com/gitlab-org/gitlab-ce/uploads/b412eeaa40c79861191d1a432d95951d/Screen_Shot_2015-10-01_at_16.03.24.png)

New awesome stuff, no scroll, grey block aligned to the bottom. 

![Screen_Shot_2015-10-01_at_16.04.08](https://gitlab.com/gitlab-org/gitlab-ce/uploads/823cdb6bfb8caec892ed001448f731e5/Screen_Shot_2015-10-01_at_16.04.08.png)

See merge request !1487

Transferring a project to another namespace updates the project's updated_at
field, but since the cache key did not depend on the object, the page fragments
were not invalidated. This resulted in stale links to the commits. Changing
the cache key to use the object pathname solves this issue.

Closes gitlab-org/omnibus-gitlab#843

This benchmark suite uses benchmark-ips
(https://github.com/evanphx/benchmark-ips) behind the scenes. Specs can
be turned into benchmark specs by setting "benchmark" to "true" in the
top-level describe block like so:

    describe SomeClass, benchmark: true do

    end

Writing benchmarks can be done using custom RSpec matchers, for example:

    describe MaruTheCat, benchmark: true do
      describe '#jump_in_box' do
        it 'should run 1000 iterations per second' do
          maru = described_class.new

          expect { maru.jump_in_box }.to iterate_per_second(1000)
        end
      end
    end

By default the "iterate_per_second" expectation requires a standard
deviation under 30% (this is just an arbitrary default for now). You can
change this by chaining "with_maximum_stddev" on the expectation:

    expect { maru.jump_in_box }.to iterate_per_second(1000)
      .with_maximum_stddev(10)

This will change the expectation to require a maximum deviation of 10%.

Alternatively you can use the it block style to write specs:

    describe MaruTheCat, benchmark: true do
      describe '#jump_in_box' do
        subject { -> { described_class.new } }

        it { is_expected.to iterate_per_second(1000) }
      end
    end

Because "iterate_per_second" operates on a block, opposed to a static
value, the "subject" method must return a Proc. This looks a bit goofy
but I have been unable to find a nice way around this.

[ci skip]

Fix: Wrong access level badge on MR comments

https://gitlab.com/gitlab-org/gitlab-ce/issues/2654

See merge request !1501

Throttle "Forgot your password?" emails

Addresses internal https://dev.gitlab.org/gitlab/gitlabhq/issues/2611

See merge request !1476

If this directory were to be empty this would result in warnings being
printed to STDERR, cluttering spec output. Doing this in Ruby fixes this
problem (and also removes the need for shell alltogether).