Add a verbose mode

[Euregan]

Hello,
I'm having trouble cloning a remote git repo, and being able to enable git's verbose mode (-vvv) would really help.
Is it possible to add an option for a verbose mode?
(Please note that cloning this repo outside of Concourse works perfectly well)

[taylorsilva]

Totally reasonable ask. Someone just has to add the code :)

[analytically]

I'll tackle this once my PR's are merged