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

Fix encrypted data backwards compatibility after upgrading attr_encrypted gem

Adds missing attribute to attr_encrypted so it is fully backwards-compatible. Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/19073

See merge request !4963

Add custom highlighting via .gitattributes

## What does this MR do?
Allows user control of language selection via a `gitlab-language` entry in `.gitattributes`

## Are there points in the code the reviewer needs to double check?
(paired with @stanhu)

## Why was this MR needed?
Guessing languages by filename is fraught and often wrong. In one project, `foo.pl` may be perl, and in another it may be prolog. Users might have a Thingfile that needs ruby highlighting, or depend on things that can't work in general, like `*.C` (capitalized) mapping to C++ instead of C.

This allows the user to override language choice so they never have to look at a mis-highlighted file.

## What are the relevant issue numbers?
https://github.com/jneen/rouge/issues/494
https://gitlab.com/gitlab-org/gitlab-ce/issues/13818 (*.tpl can't in general map to Smarty)
https://gitlab.com/gitlab-org/gitlab-ce/issues/13615 (in cases we don't have a language and mis-identify it, users could map to 'text' to turn off highlighting)

## Screenshots (if relevant)

## 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 (N/A)
- [x] 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 !4606

This reverts commit b435d7405364d28ec364072f4437512da2876762.

paired with @stanhu

Rename Licenses API to License Templates API

## What does this MR do?

Earlier I renamed this in EE, thinking license templates was an EE-only feature. This backports that change to CE. Thanks to @vsizov for pointing out this error.

See https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/400 for the EE merge request. 

See merge request !4957

Check for conflict with wiki projects when creating a new project.

## What does this MR do?
Check for conflict with wiki projects when creating a new project
## Are there points in the code the reviewer needs to double check?
No
## Why was this MR needed?
To avoid exposing the information from the wiki repository of other project
## What are the relevant issue numbers?
#18398 
## Screenshots (if relevant)
![Screen_Shot_2016-06-24_at_6.03.49_PM](/uploads/7bf55e5159bf0c2b653b8f4f941f72fc/Screen_Shot_2016-06-24_at_6.03.49_PM.png)
## Does this MR meet the acceptance criteria?

- [x] [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
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [ ] 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)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4918

Fix visibility of snippets when searching

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/18997

See merge request !1972

Fix an information disclosure when requesting access to a group containing private projects

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/19102.

The commit speaks for itself:

    Fix an information disclosure when requesting access to a group containing private projects
    
    The issue was with the `User#groups` and `User#projects` associations
    which goes through the `User#group_members` and `User#project_members`.
    
    Initially I chose to use a secure approach by storing the requester's
    user ID in `Member#created_by_id` instead of `Member#user_id` because I
    was aware that there was a security risk since I didn't know the
    codebase well enough.
    
    Then during the review, we decided to change that and directly store the
    requester's user ID into `Member#user_id` (for the sake of simplifying
    the code I believe), meaning that every `group_members` / `project_members`
    association would include the requesters by default...
    
    My bad for not checking that all the `group_members` / `project_members`
    associations and the ones that go through them (e.g. `Group#users` and
    `Project#users`) were made safe with the `where(requested_at: nil)` /
    `where(members: { requested_at: nil })` scopes.
    
    Now they are all secure.

See merge request !1973

Use `have_http_status` matcher where possible

See merge request !4955

Fix rendering of commit notes

See merge request !4953

This fix avoids exposing the information from the wiki repository of other project.

Made the search bar on emoji menu sticky

## What does this MR do?

When scrolling down the emoji menu, the search bar disappears. For better UX, the search bar no stays at the top when scrolling.

## Screenshots (if relevant)

![emoji-sticky](/uploads/a5b4773547d3d67342ddcfc07c8f1568/emoji-sticky.gif)

See merge request !4743

Update omniauth-saml to 1.6.0 to address a security vulnerability in ruby-saml

## What does this MR do?

Updates `omniauth-saml` to bring in the new `ruby-saml` dependency that addresses [CVE-2016-5697](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-5697)

Fixes #19206 

See merge request !4951

Correctly return todo ID after creating todo

See merge request !4941

Remove duplicate new page btn from edit wiki

## What does this MR do?
Removes duplicate button on wiki page

## What are the relevant issue numbers?
Closes #19075 

## Screenshots (if relevant)
![Screen_Shot_2016-06-24_at_9.45.28_AM](/uploads/8dca96c3e75b428d63acaaba6dede9a6/Screen_Shot_2016-06-24_at_9.45.28_AM.png)
![Screen_Shot_2016-06-24_at_9.45.57_AM](/uploads/e6ea97b07e48d2fe6f108d8c5a943583/Screen_Shot_2016-06-24_at_9.45.57_AM.png)

See merge request !4904

Mention gmake

Fixes https://gitlab.com/gitlab-org/gitlab-workhorse/issues/46

See merge request !4945