Bug#1133971: Acknowledgement (With 10+ apt_preferences(5) globs pinned, "apt show mg" is much slower than "apt-cache show mg")

Here's an simpler comparison showing the symptoms are definitely only 
with glob/regex patterns, not literals.


root@hera:/# printf >/etc/apt/preferences  'Pin-Priority: -1\nPin: 
version *\nPackage: %s\n' '*-dev *-devel *-dbg *-dbgsym *-prof *-src 
*-source *-dkms *-debug *-compiler *-server *-test *-tests'; time 
apt-cache policy | wc -l
14747
real    0m2.039s
user    0m1.962s
sys     0m0.087s


root@hera:/# printf >/etc/apt/preferences  'Pin-Priority: -1\nPin: 
version *\nPackage: %s\n' 
'/-(dev|devel|dbg|dbgsym|prof|src|source|dkms|debug|compiler|server|test|tests)$/'; 
time apt-cache policy | wc -l
14747
real    0m6.787s
user    0m6.764s
sys     0m0.026s


root@hera:/# printf >/etc/apt/preferences  'Pin-Priority: -1\nPin: 
version *\nPackage: %s\n' "$(apt-cache pkgnames | grep -E -e 
"-(dev|devel|dbg|dbgsym|prof|src|source|dkms|debug|compiler|server|test|tests)$" 
| tr '\n' ' ')"; time apt-cache policy | wc -l
14747
real    0m0.176s
user    0m0.140s
sys     0m0.043s