Setting the "autocrlf" Git option is an overkill since it's rarely
actually needed. More importantly, it has quite the impact on
performance (see gitlab-org/gitlab-ce#13457 for more information).

By setting "autocrlf" when creating or updating files we guarantee the
option is always set properly when we actually need it _without_
introducing overhead for requests that have nothing to do with this
option.

Fixes gitlab-org/gitlab-ce#13457

This ensures the caches for Repository#empty? and
Repository#has_visible_content? are flushed after a repository has been
imported or forked.

Fixes gitlab-org/gitlab-ce#13505

- Add `avatar_url`, `description`, `git_ssh_url`, `git_http_url`,
  `path_with_namespace` and `default_branch` in `project` in push, issue,
  merge-request and note webhooks data
- Deprecate the `ssh_url` in favor of `git_ssh_url` and `http_url` in
  favor of `git_http_url` in `project` for push, issue, merge-request and
  note webhooks data
- Deprecate the `repository` key in push, issue, merge-request and
  note webhooks data, use `project` instead

Also:
- Get rid of legacy :strict_mode
- Get rid of custom :email validator
- Add some shared examples to spec emails validation

Instead of flushing the behind/ahead counts for all branches upon every
push we now only flush the cache of branches that actually need to have
these statistics recalculated. There are now basically 2 scenarios and
their effects:

1. A user pushes a commit to the default branch, this results in the
   cache being flushed for all branches.
2. A user pushes to a non default branch, this results in _only_ the
   cache for that branch being flushed.

The existing code (Repository#expire_cache) remains backwards compatible
with the previous behaviour, the new behaviour is only applied when a
branch name is passed as an argument. This ensures that when for example
a project is deleted the cache for all branches is flushed.

`max_attachment_size` in `ApplicationSetting` should be present,
only integers greater than zero are valid.

Closes #13188

This caches the output of the following methods:

* Repository#empty?
* Repository#has_visible_content?
* Repository#root_ref

The cache for Repository#has_visible_content? is flushed whenever a
commit is pushed to a new branch or an existing branch is removed.
The cache for Repository#root_ref is only flushed whenever a user
changes the default branch of a project. The cache for Repository#empty?
is never explicitly flushed as there's no need for it.

Fixes #3903

Fixes #3339

This MR hides the 'Remove source branch' button when a new commit is added to the source branch

Instead of running ClosingIssueExtractor for every commit in a merge
request we can gather all the commit messages (and the merge request
description), concatenate all this together and then run
ClosingIssueExtractor only once.

The result of this is that MergeRequest#closes_issues is now between
3.5x and 4x faster than the old setup. Using a merge request with 10
commits (each referencing a number of issues to close) this reduced the
call duration from around 200 milliseconds to around 50 milliseconds.

As a result of these changes the Jira related tests for
MergeRequest#closes_issues have been removed. These tests stubbed
Commit#closes_issues meaning that the only code that was really tested
was the call to Array#uniq to filter out duplicate issues. As this code
is no longer used (nor present) the corresponding tests were removed.

Related: gitlab-org/gitlab-ce#12419

By simply loading the first event from the already sorted set we save
ourselves extra (slow) queries just to get the latest update timestamp.
This removes the need for Event.latest_update_time and significantly
reduces the time needed to build an Atom feed.

Fixes gitlab-org/gitlab-ce#12415

The pattern in the `::reference_pattern` class method in the
ExternalIssue model does not match all valid forms of JIRA project
names. I have updated the regex to match JIRA project names with numbers
and underscores. More information on valid JIRA project names can be
found here:
https://confluence.atlassian.com/jira/changing-the-project-key-format-192534.html

* The first character must be a letter,
* All letters used in the project key must be from the Modern Roman Alphabet and upper case, and
* Only letters, numbers or the underscore character can be used.

Gitlab::Git::Repository#branch_count is a tad faster than the previous
setup. See gitlab-org/gitlab_git!62 for more information.

Previously it was "user has already been taken", when really we were
saying the user has already been reported.

This allows us to implement artifacts passing: runner will download artifacts from all prior builds

This is needed because of backward compatibility. Previously artifacts
archive had `.tar.gz` format, but artifacts browser requires ZIP format
now.

`artifacts?` method checks if artifacts archive is available.

- Adds default values for `color` and `font` attributes
- Adds `active?`, `started?`, `ended?`, and 'status' methods

This is intended to prevent the user from creating new objects while the
transaction that removes them is being run, resulting in objects with
nil authors which can then not be edited.

See https://gitlab.com/gitlab-org/gitlab-ce/issues/7117