Bug#1014509: apt install lets me fill the filesystem

[intrigeri <intrigeri@debian.org>]

Julian Andres Klode (2022-07-07):
> My plan is to assume that Installed-Size is close enough to "size in
> /usr", and just compare that with free space in /usr with like a 100MB
> padding.
>
> This does not work for kernels which install in /boot, and if anything
> were to install stuff to /opt or /var and they are on a different FS;
> but it should be correct for most packages on a supported (usrmerged)
> system.

Sounds plenty good enough to me, it would fix the bug in the vast
majority of cases!