Bug#728775: apt-get unwarrantedly consumes input

[Zefram <zefram@fysh.org>]

Package: apt
Version: 0.9.7.9
Severity: minor

When apt-get is invoked in a way that involves actually installing a
package, it reads any available data from standard input, regardless of
actual need.  This breaks the usual ability, at an interactive shell,
to type the next command while the current one is running: apt-get
consumes input that was intended for the shell.  strace shows that the
input is read by the top-level apt-get process, by read(2) from fd 0,
in response to pselect(2).

Presumably apt-get is reading this input in order to pass it on to
interactive aspects of package installation, but it's doing it regardless
of whether the installation process seeks input and, where it does want
input, regardless of how much input it wants to read.  This behaviour
is not documented.  It's not immediately obvious why apt-get has to act
as an intermediary for this input at all.

-zefram