title: How to replace, merge, or upsert new edges in Tinkerpop
body: <p>When I try to add an edge that currently exists, for example:</p>
  
  <pre><code>g.addE('person-ip').from(g.V('customer:testID')).to(g.V('tel:5555555555')).property(id, 'testEdgeId').next()
  </code></pre>
  
  <p>I get an error like this</p>
  
  <pre><code>{"message":"Edge with id already exists: testEdgeId","Exception-Class":"java.lang.IllegalArgumentException","exceptions":["java.lang.IllegalArgumentException"],"stackTrace":"java.lang.IllegalArgumentException: Edge with id already exists: testEdgeId\n\tat org.apache.tinkerpop.gremlin.structure.Graph$Exceptions.edgeWithIdAlreadyExists(Graph.java:1141)
  </code></pre>
  
  <p>Is there any setting I can use when setting up gremlin server or the tinkergraph properties that would allow duplicate edges to be merged, upserted, or ignored? </p>