Add "compare_base.py" to help package maintenance

[fishilico]

Hello,

A few months ago I've written a small Python script which checks for updates for every base package that needs to be recompiled with SELinux support ("the -selinux packages"). Now that I've cleaned up the code and tested it today, this script is in a kind of alpha state : it is working quite well on my system but it needs to be tested and reviewed, just to be sure there is no obvious bug lying around before pushing to master...

I've written this script with the focus of keeping things simple and intuitive. So compare_base.py doesn't take any command line parameter, reads package information from base_pkglist.txt (new file written in a config-like language, with a documentation header) and downloads with yaourt -G the base packages into a base-noselinux/ directory.

From a maintainer point of view, the major difference is that base_pkglist.txt needs to be updated after each update, because the PKGBUILDs of the -selinux packages don't include the pkgrel field of the base package. This would be quite simple, but as it is easy to forget I've added a check in the script which verify that the pkgver value is the same between PKGBUILD and base_pkglist.txt. An other way of keeping track of the "base pkgrel value" could be adding a variable in PKGBUILD, but I don't like this idea much.

Here are some ideas that weren't implemented but might be added in a future version of this script, if an elegant implementation is found:

• Automatically patch the downloaded PKGBUILDs to replace ${pkgname} with ${pkgname/-selinux}, change the description text... so that the diff with the PKGBUILD of the -selinux packages is smaller.
• Print a link to the history of the base package (e.g. https://projects.archlinux.org/svntogit/packages.git/log/trunk/PKGBUILD?h=packages/systemd) when a needed update is detected, but without add too much output (maybe with an optional parameter?)

Finally, here are minor choices I've made:

• The script is compatible with both Python 2 and Python 3.
• I've put a MIT license because I don't like publishing source code with no license, but I can change to something else or remove it if this causes issues.

Nicolas

[Siosm]

Looks great, should really ease package updates! I'll test asap. Thanks.
I'll also make a new push to AUR and to my binary repository at the same time.