title: get name of pattern that matched in grok in logstash
body: <p>If I have a patterns file with a bunch of regex patterns such as the following</p>
  
  <pre><code>A .*foo.*
  B .*bar.*
  C .*baz.*
  </code></pre>
  
  <p>and my grok filter looks like the following:</p>
  
  <pre><code>grok {
    patterns_dir =&gt; ["/location/of/patterns"]
    match =&gt; { "request" =&gt; [ "%{A}", "%{B}", "%{C}",] 
   }
  }
  </code></pre>
  
  <p>is there any way to know which one matched. I.e the name of the SYNTAX. I would like to annotate the document with the name of the one that matched</p>