Feature Request: JIRA Ticket as first item of first line

I'm 100% sure that I can accomplish this same thing by using the "-c" context switch.

What I want is a system environment variable into which I can set the JIRA Ticket number (or Github issue or whatever ticketting system) and have it always appear as the first item on the first line.

What I think I'm seeing in that location now is the directory name of the repository in all uppercase followed by "-123". but that is not consistent.

If I can setup an envar like `export TICKET=xyzzy-123` then every commit I make will have my ticket number on it. When I pick up a new ticker I will change the value of $TICKET.