title: What is the purpose of proto_path in the protoc command
body: <p>My bash script has the following code generate invocation for "Protocol Buffers".</p>
  
  <pre><code>protoc --proto_path=src --java_out=src 
  src/com/domain/project/persistentThing.proto
  </code></pre>
  
  <p>That was from 2012. Today the <a href="https://developers.google.com/protocol-buffers/docs/javatutorial" rel="nofollow">online documentation for Java Protocol Buffers</a> says:</p>
  
  <pre><code>protoc -I=$SRC_DIR --java_out=$DST_DIR 
  $SRC_DIR/addressbook.proto
  </code></pre>
  
  <p>This makes it seem like <code>--proto_path</code> is superceded. What was the purpose of <code>--proto_path</code>?</p>