drill: Make a file sparse without using extra disk space

[Rodrigo Campos <rodrigo@sdfg.com.ar>]

Hi!

I've written a small simple tool to make a file sparse without using extra disk
space, it just digs holes on the file when possible. To dig the hole uses the
Linux-specific fallocate(2) syscall with FALLOC_FL_PUNCH_HOLE. So, also, it only
works on some file-systems.

Do you think that util-linux would be a good place for such a simple, linux-only
program ? The case I see it can be useful is to use on VM images file backed (or
I wrote it with this in mind, at least :)).

The code is quite simple, it's written in plain C (C99 actually) and doesn't
have any external dependencies. You can see the gitweb here:

	http://sdfg.com.ar/git/?p=drill.git

or just clone it from:

	git://sdfg.com.ar/drill.git


Given that there is a fallocate tool that uses the other mode of fallocate(2)
already, all the detection for fallocate is already there. So it should, I
guess, be easy to integrate to the code-base, adding also the #ifndef
fallocate.c has and that compatibility stuff.

Also, as you can see in the commits, I just started it some days ago. So if
you think it should have some other feature, or something else, please let me
know :)

I'm not sure how this work, but I can write a patch against util-linux if you
think it can be added. If you know there is something I should particulary take
into account for that, I will really appreciate if you let me know :)




Thanks a lot,
Rodrigo