Bug#185424: base-config: Should display progress bar while installing packages

[Colin Watson <cjwatson@debian.org>]

debconf 1.4.50 has cdebconf-style progress bar support, which will help
with this. I'll probably be working on the base-config side of this at
some point over the next month or so.

One tricky bit is that we have to use 'aptitude search' first to figure
out how long the progress bar needs to be, and then pass some hairy
arguments to aptitude to get dpkg --status-fd information. If aptitude
had some way to output progress bar information to a given file
descriptor, that would be more efficient, especially if it could process
dpkg --status-fd information itself.

We'd want a line on the file descriptor telling us how long the progress
bar should be, and then lines each time the progress bar text or
position should be updated, and probably a line at the end. The text
should be tokens rather than English strings, so that they can be
localised using debconf templates. debootstrap does this sort of thing
in its --debian-installer interaction mode.

Daniel, does this seem tractable to you? I don't know aptitude very
well, but I may be able to hack on it a bit.

Cheers,

-- 
Colin Watson                                       [cjwatson@debian.org]