branch-3. Was it a created by mistake?

[Wei-Chiu Chuang]

I just realized there is a branch-3 in the Hadoop repo. Was this created by
mistake?

I don't think we've decided to create a branch-3. It also looks like the
branch is rarely used. The last commit was

commit bf90a27b51b1f1ac102fa861eb28025d21aad19b (origin/branch-3, branch-3)
Author: Chen Liang <cli...@apache.org>
Date:   Thu Nov 29 13:31:58 2018 -0800

    HDFS-13547. Add ingress port based sasl resolver. Contributed by Chen
Liang.