lock: the correct way to do a trylock() is to use a timeout of 0

diff: change --inverse to --reverse This fixes an incompatibility with patch(1), which also uses --reverse for reversed diffs. The --inverse flag was added in 3f522d2fa633. That name was chosen over --reverse since it was thought that --reverse would make --rev ambiguous. It turns out that both flags can co-exist, with the cost that --rev can no longer be shortened to --r and --re. Since one can always use the short -r option, this is not a real problem.