Update documentation about automatic issue closing

config/gitlab.yml.example

@@ -76,7 +76,7 @@ production: &base
     # This happens when the commit is pushed or merged into the default branch of a project.
     # When not specified the default issue_closing_pattern as specified below will be used.
     # Tip: you can test your closing pattern at http://rubular.com.
-    # issue_closing_pattern: '((?:[Cc]los(?:e[sd]?|ing)|[Ff]ix(?:e[sd]|ing)?) +(?:(?:issues? +)?#\d+(?:(?:, *| +and +)?))+)'
+    # issue_closing_pattern: '((?:[Cc]los(?:e[sd]?|ing)|[Ff]ix(?:e[sd]|ing)?) +(?:(?:issues? +)?%{issue_ref}(?:(?:, *| +and +)?))+)'
 
     ## Default project features settings
     default_projects_features:

doc/customization/issue_closing.md

 # Issue closing pattern
 
-Here's how to close multiple issues in one commit message:
+When a commit or merge request resolves one or more issues, it is possible to automatically have these issues closed when the commit or merge request lands in the project's default branch.
 
-If a commit message matches the regular expression below, all issues referenced from
-the matched text will be closed. This happens when the commit is pushed or merged
-into the default branch of a project.
+If a commit message or merge request description contains a sentence matching the regular expression below, all issues referenced from
+the matched text will be closed. This happens when the commit is pushed to a project's default branch, or when a commit or merge request is merged into there.
 
-When not specified, the default issue_closing_pattern as shown below will be used:
+When not specified, the default `issue_closing_pattern` as shown below will be used:
 
 ```bash
-((?:[Cc]los(?:e[sd]?|ing)|[Ff]ix(?:e[sd]|ing)?) +(?:(?:issues? +)?#\d+(?:(?:, *| +and +)?))+)
+((?:[Cc]los(?:e[sd]?|ing)|[Ff]ix(?:e[sd]|ing)?) +(?:(?:issues? +)?%{issue_ref}(?:(?:, *| +and +)?))+)
 ```
 
+Here, `%{issue_ref}` is a complex regular expression defined inside GitLab, that matches a reference to a local issue (`#123`), cross-project issue (`group/project#123`) or a link to an issue (`https://gitlab.example.com/group/project/issues/123`).
+
 For example:
 
 ```
-git commit -m "Awesome commit message (Fix #20, Fixes #21 and Closes #22). This commit is also related to #17 and fixes #18, #19 and #23."
+git commit -m "Awesome commit message (Fix #20, Fixes #21 and Closes group/otherproject#2). This commit is also related to #17 and fixes #18, #19 and https://gitlab.example.com/group/otherproject/issues/23."
 ```
 
-will close `#20`, `#21`, `#22`, `#18`, `#19` and `#23`, but `#17` won't be closed
-as it does not match the pattern. It also works with multiline commit messages.
+will close `#18`, `#19`, `#20`, and `#21` in the project this commit is pushed to, as well as `#22` and `#23` in group/otherproject. `#17` won't be closed as it does not match the pattern. It also works with multiline commit messages.
 
 Tip: you can test this closing pattern at [http://rubular.com][1]. Use this site
 to test your own patterns.
+Because Rubular doesn't understand `%{issue_ref}`, you can replace this by `#\d+` in testing, which matches only local issue references like `#123`.
 
 ## Change the pattern
 
 For Omnibus installs you can change the default pattern in `/etc/gitlab/gitlab.rb`:
 
 ```
-issue_closing_pattern: '((?:[Cc]los(?:e[sd]|ing)|[Ff]ix(?:e[sd]|ing)?) +(?:(?:issues? +)?#\d+(?:(?:, *| +and +)?))+)'
+issue_closing_pattern: '((?:[Cc]los(?:e[sd]|ing)|[Ff]ix(?:e[sd]|ing)?) +(?:(?:issues? +)?%{issue_ref}(?:(?:, *| +and +)?))+)'
 ```
 
-For manual installs you can customize the pattern in [gitlab.yml][0].
+For manual installs you can customize the pattern in [gitlab.yml][0] using the `issue_closing_pattern` key.
 
-[0]: https://gitlab.com/gitlab-org/gitlab-ce/blob/40c3675372320febf5264061c9bcd63db2dfd13c/config/gitlab.yml.example#L65
+[0]: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/config/gitlab.yml.example
 [1]: http://rubular.com/r/Xmbexed1OJ