Adds REST API for issue relations (#7366).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@6176 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/issue.rb

@@ -501,6 +501,11 @@ class Issue < ActiveRecord::Base
   def relations
     (relations_from + relations_to).sort
   end
+  
+  # Finds an issue relation given its id.
+  def find_relation(relation_id)
+    IssueRelation.find(relation_id, :conditions => ["issue_to_id = ? OR issue_from_id = ?", id, id])
+  end
 
   def all_dependent_issues(except=[])
     except << self