I was poking at the Apache Crunch 0.9.0 release and noticed some discrepancies regarding the release tags (see https://github.com/apache/crunch/tags).
1. There is only one tag corresponding to the release - 0.9.0. There should be two tags - 0.9.0 and 0.9.0-hadoop2
2. And, the 0.9.0 tag actually corresponds to what should be tagged by 0.9.0-hadoop2. For example, if you one up the <source root>/pom.xml after checking out 0.9.0 tag, you will see crunch-parent element's version as 0.9.0-hadoop2. This, historically, has been tagged by *-hadoop2 tags.
For a moment, I thought maybe we only support hadoop2 starting 0.9.0 release but nothing in the release notes (https://issues.apache.org/jira/secure/ReleaseNote.jspa?projectId=12313526&version=12325563) or the annoucement email (https://firstname.lastname@example.org/msg01500.html) seems to suggest so.