Bug#964956: apt-cache search trips over regex special characters in package names

[Daniel Reichelt <debian@nachtgeist.net>]

Package: apt
Version: 1.8.2.1
Severity: important

Hi,

running `apt-cache search libstdc++5` on a fresh minimal system yields an empty
result. This behaviour is inconsistent with processing of command-line
arguments of the sub-commands pkgnames and show.


Environment:
- minimal buster
- sources.list: deb http://ftp.de.debian.org/debian buster main


This behaviour occurs on jessie through sid.


Here are some example commands an their respective outputs:

---------8<----------------------------
# apt-cache search libstdc++5

# apt-cache search libstdc\+\+5

# apt-cache search libstdc\\+\\+5
libstdc++5 - The GNU Standard C++ Library v3

# apt-cache search "libstdc++5"

# apt-cache search "libstdc\+\+5"
libstdc++5 - The GNU Standard C++ Library v3
--------->8----------------------------




However, the pkgnames and show sub-commands are not affected:


---------8<----------------------------
apt-cache pkgnames libstdc++5
libstdc++5

# apt-cache show libstdc++5
Package: libstdc++5
Source: gcc-3.3 (1:3.3.6ds1-30)
Version: 1:3.3.6-30
Installed-Size: 1128
[...]
--------->8----------------------------


Let me know if you need more info.

Thanks
Daniel