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

Switch back to github-linguist

Sherlock will be a new GitLab specific tool for measuring the
performance of Rails requests (and SideKiq jobs at some point). Some of
the things that are currently tracked:

* SQL queries along with their timings, backtraces and query plans
  (using "EXPLAIN ANALYZE" for PostgreSQL and regular "EXPLAIN" for
  MySQL)
* Timings of application files (including views) on a per line basis
* Some meta data such as the request method, path, total duration, etc

More tracking (e.g. Rugged or gitlab-shell timings) might be added in
the future.

Sherlock will replace any existing tools we have used so far (e.g.
active_record_query_trace and rack-mini-profiler), hence the
corresponding Gems have been removed from the Gemfile.

Sherlock can be enabled by starting Rails as following:

    ENABLE_SHERLOCK=1 bundle exec rails s

Recorded transactions can be found at `/sherlock/transactions`.

Closes #2801

Closes #2858

Closes #2866

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

This can be used to measure the time (roughly) spent on a per line
basis. This can also be used to measure timings for views, for example
by adding the following to a URL:

   ?lineprof=app/views/projects/notes/_note

rack-lineprof is only enabled when:

1. The application runs in development mode
2. The used Ruby is MRI
3. The environment variable ENABLE_LINEPROF is set to a non-empty value

This can be used to track down where queries originate from, regardless
of whether they're caused by N+1 problems or not. This can be enabled by
setting the environment variable ENABLE_QUERY_TRACE to a non-empty value
(e.g. "true").

This can be used to resolve N+1 query problems. Bullet is disabled by
default and can be enabled by starting Rails with the environment
variable ENABLE_BULLET set to a non empty value (e.g. "true").

Change "+" icon under "Files" section to have three options:

* Create file
* Upload file
* New directory

Upload file is no longer accessible from the "Create file" page.
Users can now select a target branch in upload file as well.

Closes #2799: Fixes a bug where file modes were overwritten after a commit

Closes https://github.com/gitlabhq/gitlabhq/issues/8253: Existing files
can no longer be overwritten in the "Create file" section.

Closes #2557

This allows me to use this Gem for benchmarking without having to
add/remove it every time.

This allows us to see a breakdown of API requests in New Relic.

Also update Kaminari gem to the latest version

Addresses internal https://dev.gitlab.org/gitlab/gitlabhq/issues/2605

See https://github.com/tinfoil/devise-two-factor/pull/43