Since we're making a shared library, it should be usable by non-GPL
apps.
To allow more code sharing between the core and the tests, move them
to the LGPLv2+ too.
A few bits of test and other code are still GPL. See the new COPYING
file for more information.
The data structures we use for reading already-written commits versus
building them don't need to be the same. It's cleaner if we can have
generic code which operates on a GFile implementation for reads,
because then we can share more generic code for walking and operating
on filesystem trees via GIO.
Colin Walters