Note: The special keywords in a pull request description are interpreted when the pull request targets the repository's default branch. However, if the PR's base is any other branch, then these keywords are ignored, no links are created and merging the PR has no effect on the issues. If you want to link a pull request to an issue using a keyword, the PR must be on the default branch.
About linked issues and pull requests
You can link an issue to a pull request using a supported keyword in the pull request description.
When you link a pull request to the issue the pull request addresses, collaborators can see that someone is working on the issue. If the pull request and the issue are in different repositories, GitHub Enterprise Server will display the link after the pull request is merged, if the person who merges the pull request also has permission to close the issue.
When you merge a linked pull request into the default branch of a repository, its linked issue is automatically closed. For more information about the default branch, see "Changing the default branch."
Linking a pull request to an issue using a keyword
You can link a pull request to an issue by using a supported keyword in the pull request's description or in a commit message (please note that the pull request must be on the default branch).
The syntax for closing keywords depends on whether the issue is in the same repository as the pull request.
|Issue in the same repository||KEYWORD #ISSUE-NUMBER|
|Issue in a different repository||KEYWORD OWNER/REPOSITORY#ISSUE-NUMBER|
|Multiple issues||Use full syntax for each issue|
You can also use closing keywords in a commit message. The issue will be closed when you merge the commit into the default branch, but the pull request that contains the commit will not be listed as a linked pull request.