Clean up package list parsing

[bcoles]

This PR adds _ to the package pattern match for RHEL: '\.el[1-9]+[\._]'.

This PR also reworks the package list parsing for each OS, such that cat is no longer required.

head is still used, but moved to the end of the expression, so that elif doesn't complain.

The use of head -1 could probably be replaced with [ -z "$str" ] expression; however, I didn't implement this as I couldn't be bothered testing on a bunch of systems and versions of Bash.

Issue

LES uses regex pattern matching on the first line (head -1 ...) of the package list to determine to the package list format and OS.

The match is insufficient for RHEL systems, as there's no guarantee that the first line will contain the el[0-9] pattern.

For example, the following output is from rpm -qa on a RHEL5.5 box:

# head -n 20 pkg 
tzdata-2010e-1.el5
gnome-audio-2.0.0-3.1.1
redhat-release-notes-5Server-31
libstdc++-4.1.2-48.el5
info-4.8-14.el5
freetype-2.2.1-21.el5_3
db4-4.3.29-10.el5
zlib-1.2.3-3
freetype-2.2.1-21.el5_3
libjpeg-6b-37
ncurses-5.5-24.20060715
keyutils-libs-1.2-1.el5
time-1.7-27.2.2
pax-3.4-2.el5
dmidecode-2.10-3.el5
libjpeg-6b-37
libXau-1.0.1-3.1
groff-1.18.1.1-11.1
bc-1.06-21
ethtool-6-4.el5

Additionally, when el[0-9] is present in the package name, there's no guarantee that the package name format will always match the \.el[0-9]+\. pattern. For example, on RHEL 5, the pattern el5_ is often used, rather than a el5..

# cat pkg | head -50 | grep -E '\.el[1-9]+\.'
# cat pkg | head -50 | grep -E '\.el[1-9]+[\._]'
freetype-2.2.1-21.el5_3
freetype-2.2.1-21.el5_3
cyrus-sasl-plain-2.1.22-5.el5_4.3
speex-1.0.5-4.el5_1.1
neon-0.25.5-10.el5_4.1
# cat pkg |  grep -E '\.el[1-9]+\.'
automake16-1.6.3-8.el5.1
tmpwatch-2.9.7-1.1.el5.2
automake15-1.5-16.el5.2
automake17-1.7.9-7.el5.2
m4-1.4.5-3.el5.1
m2crypto-0.16-6.el5.6
usermode-1.88-3.el5.2
usermode-gtk-1.88-3.el5.2
hwdata-0.213.18-1.el5.1
automake14-1.4p6-13.el5.1
stunnel-4.15-2.el5.1
mlocate-0.15-1.el5.2

# cat pkg |  grep -E '\.el[1-9]+[\._]' | wc -l
98
# cat pkg |  grep -E '\.el[1-9]+\.' | wc -l
12
# cat pkg |  grep -E '\.el[1-9]+_' | wc -l
86

[mzet-]

Good catch. Thanks.