better gem's version control for prevent dependency errors.

require: nil and require: false get same result, but i think we shouldn't write it differently in other places.

Add troubleshooting section for SMTP settings



See merge request !5046

Added user avatar to header

## What does this MR do?

Adds  the users avatar to the header with a dropdown for profile & sign out.

## What are the relevant issue numbers?

Closes #18543 

## Screenshots (if relevant)

![Screen_Shot_2016-06-27_at_12.47.34](/uploads/852d0eb7075eefcf21f5cf5ff71a389a/Screen_Shot_2016-06-27_at_12.47.34.png)

![Screen_Shot_2016-06-27_at_12.47.36](/uploads/6cb29843d3a12bbf2d3ed2a7c9bde770/Screen_Shot_2016-06-27_at_12.47.36.png)

See merge request !4939

Handle custom Git hook result in GitLab UI

## What does this MR do?

This MR fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/19190
It allows to show messages from git custom hooks

## Screenshots (if relevant)

![joxi_screenshot_1467651998090](/uploads/7f814523c96712c07b4f4b52c843aab3/joxi_screenshot_1467651998090.png)

See merge request !5073

Fix dead links in the docs (Jun 2016)

## What does this MR do?

Fix dead links in the docs found as of Jun 2016.

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

n/a

## Why was this MR needed?

This MR must improve UX on docs.gitlab.com.

## What are the relevant issue numbers?

Closes #19156 

## Does this MR meet the acceptance criteria?

- No [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) updated
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [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 !4921

Upgrade rspec-rails from 3.4.2 to 3.5.0.

Also upgrade its dependencies. Includes Rails 5 support. Working toward #14286 

Changelogs: http://rspec.info/blog/2016/07/rspec-3-5-has-been-released/

See merge request !5051

Update README.md - SSH password can be changed with `ssh-keygen -p`

SSH password can be changed with `ssh-keygen -p`

See merge request !4152

Save artifacts sizes

## What does this MR do?

Introduce ci_builds.artifacts_size as an integer, so that it's easier to access than reading from the file again.

## What are the relevant issue numbers?

Closes #18869

See merge request !4964

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4964/diffs#note_12867416

Guidelines:
https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/testing.md#general-guidelines

> Use `context` to test branching logic.

Feedback from:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4964#note_12867273

Update spring to 1.7.2 to fix hanging rails console

## What does this MR do?
Update spring to 1.7.2.

## Why was this MR needed?
This fixes hanging rails console issue.

## Related
Fixes https://gitlab.com/gitlab-org/gitlab-development-kit/issues/127

## 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
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] 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 !5066

More descriptive message for git hooks and file locks

## What does this MR do?
Most of the benefits will be in GitLab EE because we have git hooks there (push rules) and file lock features.
Instead of showing "Git operation was rejected by #{hook_name} hook" the actual problem description will be shown.
Also you will see a clear message when you edit locked file.

## Why was this MR needed?

Because we don't want to confuse our users

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ee/issues/713


See merge request !5067

* upstream/master: (175 commits)
  Document Repository#keep_around
  Don't garbage collect commits that have related DB records like comments
  Update CHANGELOG
  Update RedCloth to 4.3.2 for CVE-2012-6684
  Fix typo in Merge Requests API documentation
  Downgrade to Redis 3.2.2 due to massive memory leak with Sidekiq
  Enable Style/EmptyLines cop, remove redundant ones
  Update CHANGELOG
  Cache results from jQuery selectors to retrieve namespace name
  Fix import button when import fail due the namespace already been taken
  Fix snippets comments not displayed
  Fix emoji paths in relative root configurations
  Exclude requesters from Project#members, Group#members and User#members
  Upgrade Thin from 1.6.1 to 1.7.0.
  Many squashed commits
  Cache autocomplete results
  Upgrade Sidekiq from 4.1.2 to 4.1.4.
  Upgrade seed-fu from 2.3.5 to 2.3.6
  use has_many relationship with events
  Support creating a todo on issuables via API
  ...

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4964#note_12861588

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4964#note_12861577

Don't garbage collect commits that have related DB records like comments

Closes #13524

Also needed for https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4101.

See merge request !5062

Downgrade to Redis 3.2.2 due to massive memory leak with Sidekiq

This affects GitLab 8.8 and 8.9. See:
    
* https://github.com/mperham/sidekiq/blob/master/Changes.md#413
* https://gitlab.com/gitlab-org/gitlab-ce/issues/19441

See merge request !5056

Update RedCloth to 4.3.2 for CVE-2012-6684

## What does this MR do?

To fix XSS (CVE-2012-6684), upgrade RedCloth to 4.3.2.

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

No.

## Why was this MR needed?

Security vulnerability in RedCloth (CVE-2012-6684) should be fixed to provide GitLab as a secure software.

## What are the relevant issue numbers?

Closes #19169 

cf. !2037, !2071

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [n/a] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [n/a] API support added
- Tests
  - [n/a] 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 !4929

Merge branch '19448-merge-requests-api-has-incorrect-documentation-regarding-merge_when_build_succeeds' into 'master'

Fix typo in Merge Requests API documentation

Closes #19448

See merge request !5057

* master: (98 commits)
  Enable Style/EmptyLines cop, remove redundant ones
  Update CHANGELOG
  Cache results from jQuery selectors to retrieve namespace name
  Fix import button when import fail due the namespace already been taken
  Fix snippets comments not displayed
  Fix emoji paths in relative root configurations
  Exclude requesters from Project#members, Group#members and User#members
  Upgrade Thin from 1.6.1 to 1.7.0.
  Many squashed commits
  Cache autocomplete results
  Upgrade Sidekiq from 4.1.2 to 4.1.4.
  Upgrade seed-fu from 2.3.5 to 2.3.6
  use has_many relationship with events
  Support creating a todo on issuables via API
  Expose target, filter by state as string
  Add todos API documentation and changelog
  Improve the request / withdraw access button
  Metrics for Rouge::Plugins::Redcarpet and Rouge::Formatters::HTMLGitlab
  Groundwork for Kerberos SPNEGO (EE feature)
  Update CHANGELOG 8.9.5 for runners related fixes
  ...

See:

https://github.com/mperham/sidekiq/blob/master/Changes.md#413
https://gitlab.com/gitlab-org/gitlab-ce/issues/19441

Groundwork for Kerberos SPNEGO (EE feature)

Refactor Projecst::GitHttpController to allow Kerberos integration in GitLab EE.

Companion to https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/509

See merge request !5037

Exclude requesters from Project#members, Group#members and User#members

## What does this MR do?

It excludes requesters from the `Project#members`, `Group#members` and `User#members` associations, and adds new `Project#requesters` and `Group#requesters` associations.

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

No.

## Why was this MR needed?

Without this, if you call `project.members`, requesters are included in the results! This is at best misleading, and at worst can lead to security issues. By excluding requesters from the `#members` associations, we avoid introducing security inadvertently since you have to call the `#requesters` association explicitly to get requesters.

## What are the relevant issue numbers?

This is something I realized while fixing the security issue #19102.

## Does this MR meet the acceptance criteria?

- [x] I don't think this needs a CHANGELOG since this is an internal change
- Tests
  - [x] 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 !4946

Upgrade Sidekiq from 4.1.2 to 4.1.4.

Adds a dependency on Sinatra and allows Sinatra 2 for eventual support of Rack 2.

Changelog: https://github.com/mperham/sidekiq/blob/master/Changes.md#414

Working toward #14286. 

See merge request !5044

Upgrade seed-fu from 2.3.5 to 2.3.6

Adds Rails 5 support. Working toward #14286.

Changelog: https://github.com/mbleigh/seed-fu/blob/master/CHANGELOG.md#version-236

See merge request !5042

Upgrade sass-rails

## What does this MR do?

Upgrades sass-rails from 5.0.4 to 5.0.5. Includes support for Rails 5.

Changelog: https://github.com/rails/sass-rails/releases

Working toward #14286 

See merge request !5030

Enable Style/EmptyLines Rubocop cop

#17478

See merge request !5013

Renable import button when import process fail due to the namespace already been taken

Closes #19435 

## Screenshots (if relevant)

Before:

![1](/uploads/e8de1b326e0751891f667630a7685f6a/1.png)<br/><br/>

After:

![2](/uploads/566f1fd5442c28232350689fce8eae76/2.png)

See merge request !5053