JQL function for showing all issues linked to any issue by a given issue link type

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Function linkedIssues() only shows the issues linked to a particular issue, I want to find all issues those are linked to other issues marked by a specific link type, e.g., "is blocked by".

This function could incorporate querying issues that are linked to any issue with a given link type and bearing in mind that links have two identities, one in each direction, the link type could be direction specific or not.

Examples

1. find all issues that are duplicates of issue JRA-25640 (one direction, issue specified)
2. find all issues that are blocking issue JRA-25640 or that JRA-25640 blocks (bidirectional, issue specified)
3. find all issues that are duplicates of any issue, or which duplicate any issue (bidirectional, no issue specified)
4. find all issues that are blocked (one direction, no issue specified)

Implementation Notes

• The JQL function that exists must continue to work exactly as it does. If it is possible to overload the JQL function based on arity and this makes a consistent API, then this would be preferred. Otherwise, there may need to be a new function name which provides vararg behaviour as described above.
• The link index entries added in 4.4 (I think) provide enough to build performant lucene queries for the above use cases. What's missing is the JQL function plumbing.