Merge branch 'master' into 34312-eslint-vue-plugin

* master: (78 commits)
  Use --left-right and --max-count for counting diverging commits
  API: get participants from merge_requests & issues
  Copy Mermaid graphs as GFM
  Rephrase paragraph about e2e tests in merge requests in docs
  Remove EE only sections from docs
  Update redis-rack to 2.0.4
  Refactor matchers for background migrations
  Add id to modal.vue to support data-toggle="modal"
  Allow local tests to use a modified Gitaly
  Fix specs
  Use computed prop in expand button
  Update check.md
  add deprecation and removal issue to docs
  Add status attribute to runner api entity
  Fix typos in a code comment
  Refactor RelativePositioning so that it can be used by other classes
  Backport 'Rebase' feature from EE to CE
  Just try to detect and assign once
  Fix custom name in branch creation for issue in Firefox
  Modify `LDAP::Person` to return username value based on attributes
  ...

4 files changed, 114 insertions, 0 deletions

diff --git a/doc/development/gitaly.md b/doc/development/gitaly.md
index ca2048c7019..26abf967dcf 100644
--- a/doc/development/gitaly.md
+++ b/doc/development/gitaly.md
@@ -97,6 +97,29 @@ describe 'Gitaly Request count tests' do
 end
 ```
 
+## Running tests with a locally modified version of Gitaly
+
+Normally, gitlab-ce/ee tests use a local clone of Gitaly in `tmp/tests/gitaly`
+pinned at the version specified in GITALY_SERVER_VERSION. If you want
+to run tests locally against a modified version of Gitaly you can
+replace `tmp/tests/gitaly` with a symlink.
+
+```shell
+rm -rf tmp/tests/gitaly
+ln -s /path/to/gitaly tmp/tests/gitaly
+```
+
+Make sure you run `make` in your local Gitaly directory before running
+tests. Otherwise, Gitaly will fail to boot.
+
+If you make changes to your local Gitaly in between test runs you need
+to manually run `make` again.
+
+Note that CI tests will not use your locally modified version of
+Gitaly. To use a custom Gitaly version in CI you need to update
+GITALY_SERVER_VERSION. You can use the format `=revision` to use a
+non-tagged commit from https://gitlab.com/gitlab-org/gitaly in CI.
+
 ---
 
 [Return to Development documentation](README.md)
diff --git a/doc/development/testing_guide/end_to_end_tests.md b/doc/development/testing_guide/end_to_end_tests.md
new file mode 100644
index 00000000000..abe5b06e0f0
--- /dev/null
+++ b/doc/development/testing_guide/end_to_end_tests.md
@@ -0,0 +1,80 @@
+# End-to-End Testing
+
+## What is End-to-End testing?
+
+End-to-End testing is a strategy used to check whether your application works
+as expected across entire software stack and architecture, including
+integration of all microservices and components that are supposed to work
+together.
+
+## How do we test GitLab?
+
+We use [Omnibus GitLab][omnibus-gitlab] to build GitLab packages and then we
+test these packages using [GitLab QA][gitlab-qa] project, which is entirely
+black-box, click-driven testing framework.
+
+### Testing nightly builds
+
+We run scheduled pipeline each night to test nightly builds created by Omnibus.
+You can find these nightly pipelines at [GitLab QA pipelines page][gitlab-qa-pipelines].
+
+### Testing code in merge requests
+
+It is possible to run end-to-end tests (eventually being run within a
+[GitLab QA pipeline][gitlab-qa-pipelines]) for a merge request by triggering
+the `package-qa` manual action, that should be present in a merge request
+widget.
+
+Mmanual action that starts end-to-end tests is also available in merge requests
+in Omnibus GitLab project.
+
+Below you can read more about how to use it and how does it work.
+
+#### How does it work?
+
+Currently, we are using _multi-project pipeline_-like approach to run QA
+pipelines.
+
+1. Developer triggers a manual action, that can be found in CE and EE merge
+requests. This starts a chain of pipelines in multiple projects.
+
+1. The script being executed triggers a pipeline in GitLab Omnibus and waits
+for the resulting status. We call this a _status attribution_.
+
+1. GitLab packages are being built in Omnibus pipeline. Packages are going to be
+pushed to Container Registry.
+
+1. When packages are ready, and available in the registry, a final step in the
+pipeline, that is now running in Omnibus, triggers a new pipeline in the GitLab
+QA project. It also waits for a resulting status.
+
+1. GitLab QA pulls images from the registry, spins-up containers and runs tests
+against a test environment that has been just orchestrated by the `gitlab-qa`
+tool.
+
+1. The result of the GitLab QA pipeline is being propagated upstream, through
+Omnibus, back to CE / EE merge request.
+
+#### How do I write tests?
+
+In order to write new tests, you first need to learn more about GitLab QA
+architecture. See the [documentation about it][gitlab-qa-architecture] in
+GitLab QA project.
+
+Once you decided where to put test environment orchestration scenarios and
+instance specs, take a look at the [relevant documentation][instance-qa-readme]
+and examples in [the `qa/` directory][instance-qa-examples].
+
+## Where can I ask for help?
+
+You can ask question in the `#qa` channel on Slack (GitLab internal) or you can
+find an issue you would like to work on in [the issue tracker][gitlab-qa-issues]
+and start a new discussion there.
+
+[omnibus-gitlab]: https://gitlab.com/gitlab-org/omnibus-gitlab
+[gitlab-qa]: https://gitlab.com/gitlab-org/gitlab-qa
+[gitlab-qa-pipelines]: https://gitlab.com/gitlab-org/gitlab-qa/pipelines
+[gitlab-qa-architecture]: https://gitlab.com/gitlab-org/gitlab-qa/blob/master/docs/architecture.md
+[gitlab-qa-issues]: https://gitlab.com/gitlab-org/gitlab-qa/issues
+[instance-qa-readme]: https://gitlab.com/gitlab-org/gitlab-ce/tree/master/qa/README.md
+[instance-qa-examples]: https://gitlab.com/gitlab-org/gitlab-ce/tree/master/qa/qa
diff --git a/doc/development/testing_guide/index.md b/doc/development/testing_guide/index.md
index 65386f231a0..74d09eb91ff 100644
--- a/doc/development/testing_guide/index.md
+++ b/doc/development/testing_guide/index.md
@@ -65,6 +65,13 @@ Everything you should know about how to test Rake tasks.
 
 ---
 
+## [End-to-end tests](end_to_end_tests.md)
+
+Everything you should know about how to run end-to-end tests using
+[GitLab QA][gitlab-qa] testing framework.
+
+---
+
 ## Spinach (feature) tests
 
 GitLab [moved from Cucumber to Spinach](https://github.com/gitlabhq/gitlabhq/pull/1426)
@@ -89,3 +96,4 @@ test should be re-implemented using RSpec instead.
 [Capybara]: https://github.com/teamcapybara/capybara
 [Karma]: http://karma-runner.github.io/
 [Jasmine]: https://jasmine.github.io/
+[gitlab-qa]: https://gitlab.com/gitlab-org/gitlab-qa
diff --git a/doc/development/testing_guide/testing_levels.md b/doc/development/testing_guide/testing_levels.md
index 1cbd4350284..4adf0dc7c7a 100644
--- a/doc/development/testing_guide/testing_levels.md
+++ b/doc/development/testing_guide/testing_levels.md
@@ -121,6 +121,9 @@ running feature tests (i.e. using Capybara) against it.
 The actual test scenarios and steps are [part of GitLab Rails] so that they're
 always in-sync with the codebase.
 
+Read a separate document about [end-to-end tests](end_to_end_tests.md) to
+learn more.
+
 [multiple pieces]: ../architecture.md#components
 [GitLab Shell]: https://gitlab.com/gitlab-org/gitlab-shell
 [GitLab Workhorse]: https://gitlab.com/gitlab-org/gitlab-workhorse