Fix emails on push diff limit

The diff limits were not respected in the emails-on-push since the refactoring in gitlab-org/gitlab-ce!2705. This was one possible cause for customer issue described in gitlab-org/gitlab-ce#15137.

This MR also brings in the changes in !337 since they are required for this to work.


See merge request !338

Minimal implementation for Safe Webhooks

This will be used by Geo #76, and will be improved for 8.8 in gitlab-org/gitlab-ce#13478

See merge request !334

Possible cause of issues in gitlab-org/gitlab-ce#15137

`safe_diff_files` directly modifies @message.diffs and was being called inside the HTML template
of the e-mail. By the time the text e-mail rendering occurs, the objects were already
wrapped by GitLab's diff helpers. This MR makes it explicit that the diff wrapper
will be used in both the text and HTML e-mail templates.

Closes gitlab-org/gitlab-ce#14497

Add ability to push to remote repositories

Closes #116 

See merge request !249

* Use Rugged filters to work with local/remote branches.
* Rename Project#remote_mirror? to Project#has_remote_mirror?
* Use delegate pattern for Repository#push_remote_branches and Repository#delete_remote_branches
* Make Repository#remote_tags return Gitlab::Git::Tag objects.
* Refactor Repository#remote_branches
* Rename Repository#push_branches to Repository#push_remote_branches
* Made other small refactors to views and specs.
* Make encrypted_credentials column size bigger.
  This was giving problems with MySql for large passwords.
* Refactor for UpdateRemoteMirrorService spec so we no longer
  harcode the branch names and specs are not broken after `gitlab-test`
  project is updated.

* Also fixed couple of small bugs introduced with last changes

* Also addressed feedback from https://gitlab.com/gitlab-org/gitlab-ee/commit/fcbfe56207f64da07deb7f3a8cbdcd505069edbd

* Now #url= and #url always handle the full URL, encryption is done transparently
* #safe_url was added for future purposes
* Little refactor for UpdateRemoteMirrorService

* Also added small fix for the scenario when the remote repo is empty
 and does not have tags.

* Add the ability to skip tags when fetching a remote repo.
  See: https://gitlab.com/gitlab-org/gitlab-shell/merge_requests/46

Merge branch 'regression-ldap-group-synchronization-is-broken-for-our-company-s-ldap-with-gitlab-8-6-442' into 'master'

Fix LDAP group sync regression for groups with member value `uid=<username>`

Closes #442 

See merge request !335

Add specs for Projects::ApproversController



See merge request !327

[Elastic] Stabilize database indexer if database is inconsistent

Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/459

See merge request !328

update gitlab-elastic-search gem

Fixes https://gitlab.com/gitlab-org/gitlab-elasticsearch-git/issues/3

See merge request !330

Instrument Rails cache code

See merge request !3619

Update gitlab-shell to 2.7.2

See merge request !3594

Use meta key to open todo in new tab

Fixes #15078 

See merge request !3623

Remove TODO for not documented stuff

We should not put a `TODO` in a released product.

See merge request !3553

First pass at a Testing styleguide

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/14121

[ci skip]

See merge request !3465

Use more accurate timestamps for InfluxDB.

See merge request !3617

This allows us to track how much time of a transaction is spent in
dealing with cached data.

Use gitlab-workhorse 0.7.2

See merge request !3570

This is the inverse of 51894dbb.

This changes the timestamp of metrics to be more accurate/unique by
using Time#to_f combined with a small random jitter value. This
combination hopefully reduces the amount of collisions, though there's
no way to fully prevent any from occurring.

Fixes gitlab-com/operations#175

API: Expose subscribed? on issues and merge requests

This is the first start for the new `subscribable` API. It exposes the `subscribed` field for issues and merge requests.

Related to #6024

See merge request !3611

Fix Incorrect Quote In Docker Executor Example

## What does this MR do?
The corrected line opened with a regular quote (') but closed with a back-tick (`)  
I believe this is invalid bash syntax

## Are there points in the code the reviewer needs to double check?
Probably not

## Why was this MR needed?
Fixes error when example is copied and pasted

## What are the relevant issue numbers?
None

## Screenshots (if relevant)
None

See merge request !3604