common: stop installing archlinux-contrib

It was installed for checkservices which we rarely use anymore due to
automated updates. Also, update README.md to remove references to it.

README.md

@@ -123,19 +123,10 @@ Arch-audit can be used to find servers in need of updates for security issues.
 
     ansible all -a "arch-audit -u"
 
-#### Updating servers
+### Semi-automated server upgrades
 
-The following steps should be used to update our managed servers:
-
-  * pacman -Syu
-  * sync
-  * checkservices
-  * reboot
-
-##### Semi-automated server updates (experimental)
-
-For updating a lot of servers in a more unattended manner, the following
-playbook can be used:
+For updating all servers in a mostly unattented manner, the following playbook
+can be used:
 
     ansible-playbook playbooks/tasks/upgrade-servers.yml [-l SUBSET]
 

roles/common/tasks/main.yml

@@ -150,8 +150,8 @@
     - zshrc
     - dircolors
 
-- name: Install pacman-contrib and archlinux-contrib
-  pacman: name=pacman-contrib,fakeroot,archlinux-contrib state=installed
+- name: Install pacman-contrib for paccache/pacdiff and fakeroot for checkupdates
+  pacman: name=pacman-contrib,fakeroot state=installed
 
 - name: Install custom paccache.service
   copy: src=paccache.service dest=/etc/systemd/system/paccache.service owner=root group=root mode=0644