Bug#909155: apt-cache show multiple packages produces invalid output

[Helmut Grohne <helmut@subdivi.de>]

Package: apt
Version: 1.7.0~rc1
Severity: serious
File: /usr/bin/apt-cache

If you do a fresh sid debootstrap and then you can get the following
interaction:

$ apt-cache show gcc-8-base=installed libgcc1=installed
Package: gcc-8-base
Source: gcc-8
Version: 8.2.0-7
Installed-Size: 244
Maintainer: Debian GCC Maintainers <debian-gcc@lists.debian.org>
Architecture: amd64
Breaks: gcc-4.4-base (<< 4.4.7), gcc-4.7-base (<< 4.7.3), gcj-4.4-base (<< 4.4.6-9~), gcj-4.6-base (<< 4.6.1-4~), gnat-4.4-base (<< 4.4.6-3~), gnat-4.6 (<< 4.6.1-5~)
Description: GCC, the GNU Compiler Collection (base package)
Description-md5: b6e93638a6d08ea7a18929d7cf078e5d
Multi-Arch: same
Homepage: http://gcc.gnu.org/
Tag: role::shared-lib
Section: libs
Priority: optional
Filename: pool/main/g/gcc-8/gcc-8-base_8.2.0-7_amd64.deb
Size: 187052
MD5sum: 5ae3d2f575c9924ae67fa8dcc4af1e21
SHA256: 9e3dcd13005ccadbb57a8f117cde66aec8b8b8a21492e3aa02d6f54c1288bfb4

Package: libgcc1
Source: gcc-8 (8.2.0-7)
Version: 1:8.2.0-7
Installed-Size: 116
Maintainer: Debian GCC Maintainers <debian-gcc@lists.debian.org>
Architecture: amd64
Depends: gcc-8-base (= 8.2.0-7), libc6 (>= 2.14)
Breaks: gcc-4.3 (<< 4.3.6-1), gcc-4.4 (<< 4.4.6-4), gcc-4.5 (<< 4.5.3-2)
Description: GCC support library
Description-md5: bbd60d723e97d8e06c04228ee4c76f10
Tag: role::shared-lib
Section: libs
Priority: optional
Filename: pool/main/g/gcc-8/libx32gomp1_8.2.0-7_amd64.deb
Size: 77204
MD5sum: 61275848d23df37f647cb6a9b21f4135
SHA256: b8c56221460897e2640baf7bd6e1a9f645346d4178265508a18d48bf8c68e752

Package: libx32gomp1-dbg
Source: gcc-8
Version: 8.2.0-7
Installed-Size: 346
Maintainer: Debian GCC Maintainers <de
$

Please observe that a third package is included, but truncated. This is
just an example. For other combinations of packages, you get other
invalid output. I've also seen "Multi-Arch: forei" and other crap.

I'm filing this at severity serious, because I think it is the tip of an
iceberg. The rc severity will prevent apt-listbugs users from installing
to leave time for investigation. Please downgrade the severity once the
problem is understood to be harmless.

Helmut