[pacman-dev] Checking free space before transaction

Hi,

I have implemented some basic disk space checking in pacman.  The code 
is still a bit rough and there are some TODOs in there (especially 
related to output).  But the basics are all there, so it seems time to 
get some comments.

See my diskspace branch:
http://projects.archlinux.org/users/allan/pacman.git/log/?h=diskspace

Obviously I need to do some rebasing there, so it is probably easiest to 
look at the diff between that and my working branch:
http://projects.archlinux.org/users/allan/pacman.git/diff/?h=diskspace&id2=working

Here are some basic examples of what is implemented so far:


 > sudo src/pacman/pacman -S grub --dbpath /home/allan/tmp/db/
...
(1/1) checking for file conflicts 
[######################] 100%
Partition: /
  - blocks needed: 112
  - blocks free: 2635828
Partition: /boot
  - blocks needed: 1
  - blocks free: 109046
(1/1) installing grub 
[######################] 100%


 > sudo src/pacman/pacman -S grub --dbpath /home/allan/tmp/db/
...
(1/1) checking for file conflicts 
[######################] 100%
Partition: /
  - blocks needed: 0
  - blocks free: 2635684
Partition: /boot
  - blocks needed: 0
  - blocks free: 109044
(1/1) upgrading grub 
[######################] 100%


It also handles the space freed by removing conflicts etc.

Obviously the space calculations could be improved, e.g.
  - for /boot on installing grub, the /boot/grub directory should 
require a block in addition to the one used by the menu.lst file
  - directories get counted for removal even when they are not being 
removed... and that multiplies across packages
  - .PKGINFO etc count towards / (rather than to dbpath ???)
  - space for .pacnew/.pacsave files is ignored

But it is close enough...  In its current form the calculations should 
catch major stupidity.

Allan