title: CircleCI - regex filtering match within string
body: <p>I'm trying to filter to make sure the branch has a jira ticket name in it. The ticket name can be anywhere in the branch name.</p>
  
  <pre><code>      - uploadToJira:
            requires:
              - testDebug
              - testRelease
            filters:
              branches:
                only: /.*(jira|JIRA)-\d+.*/
  </code></pre>
  
  <p>This should match names like <code>feature-JIRA-18889-test</code> or <code>bug-JIRA-2344</code> or <code>jira-1233</code>, but it does not seem to do so (though the same regex works in Java). What am I doing wrong?</p>
  
  <p>Update: The regex <code>/^pull.*/</code> works, which tells me it's matching on the pull request name for the branch (which is what circleci uses when it checks the code out). This seems like a bug in circleci, since <code>pull/383</code> doesn't leave you with enough information to match on branch name; they'll all be the same.</p>