Modify org.apache.zookeeper.version.Info.REVISION to store git repo revision
Currently org.apache.zookeeper.version.Info.REVISION stores the svn repo revision which is of type int
But after migrating to git repo the git repo's revision(commit 63f5132716c08b3d8f18993bf98eb46eb42f80fb) can not be stored in this variable.
So either we should modify this variable to string to introduce new variable to store the git revision and leave the svn revision variable unchanged.
build.xml, and org.apache.zookeeper.version.util.VerGen also need to be modified.