An NSSaveChangesRequest subclass that commits rather than just saves.

Example committing whatever was last saved:

	GitCommitChangesRequest * commit = [[GitCommitChangesRequest alloc] init];
	commit.message = …
	commit.author = …
	commit.email = …

	NSError * error = nil;
	[self.managedObjectContext.persistentStoreCoordinator executeRequest:commit withContext:self.managedObjectContext error:&error];
Remove nested folders for uuids.
Go back to preserving the index file between commits.