Check those commit messages please!

[Josh Elser]

I'm noticing some recent commits on Avatica where we have no lineage on 
what JIRA issue the change was for. Please make sure you have the 
"[CALCITE-XXXX]" included in the commit message when we're not dealing 
with something trivial.

No need to ACK this, take responsibility, or anything of the such. We've 
all done it in the past, just wanted to drop a reminder :)

Thanks!