public Builder clearRevisionId() {
      revisionId_ = getDefaultInstance().getRevisionId();
      bitField0_ = (bitField0_ & ~0x00000002);
      onChanged();
      return this;
    }
<pre>
Optional. The revision of the workflow to retrieve. If the revision_id is
empty, the latest revision is retrieved.
The format is "000001-a4d", where the first six characters define
the zero-padded decimal revision number. They are followed by a hyphen and
three hexadecimal characters.
</pre>

<code>string revision_id = 2 [(.google.api.field_behavior) = OPTIONAL];</code>

@return This builder for chaining.
java-workflows/proto-google-cloud-workflows-v1/src/main/java/com/google/cloud/workflows/v1/GetWorkflowRequest.java