HACKING: add some info about metadata in git commit messages
HACKING: add some info about metadata in git commit messages

The first item in this list is actually related to git commit
messages, but next three are actually consequences of the first
(assumptions we've had over the years which were not written before).

babycaseny/banshee,GNOME/banshee,babycaseny/banshee,ixfalia/banshee,Carbenium/banshee,arfbtwn/banshee,arfbtwn/banshee,ixfalia/banshee,arfbtwn/banshee,ixfalia/banshee,babycaseny/banshee,GNOME/banshee,GNOME/banshee,Carbenium/banshee,stsundermann/banshee,stsundermann/banshee,ixfalia/banshee,GNOME/banshee,ixfalia/banshee,GNOME/banshee,stsundermann/banshee,Carbenium/banshee,babycaseny/banshee,arfbtwn/banshee,babycaseny/banshee,arfbtwn/banshee,stsundermann/banshee,arfbtwn/banshee,stsundermann/banshee,stsundermann/banshee,Carbenium/banshee,Carbenium/banshee,ixfalia/banshee,GNOME/banshee,ixfalia/banshee,stsundermann/banshee,GNOME/banshee,arfbtwn/banshee,arfbtwn/banshee,Carbenium/banshee,stsundermann/banshee,ixfalia/banshee,GNOME/banshee,babycaseny/banshee,babycaseny/banshee,babycaseny/banshee