Minor Description
Bigtop before BIGTOP-2306 uses Grgit (groovy git) to clone git repos. Under the covers Grgit uses JGit. JGit's clone commend does not fetch any submodules during clone unless asked, and grgit does not ask. After BIGTOP-2306 we still should initialize and update submodules unconditionally. It's harmless to do this on repos which don't use submodules, and broken not to do so on repos which do use them.