Can someone please point me to a -good- resource which explains how to update Git on Mac? I have version 1.8.4.2 running but the documentation on the Github site is conflicting and cunfusing.

Look here:
http://git-scm.com/downloads
On the right a big notification "Latest source Release 2.2.1" "Downloads for Mac". But clicking through you get to this page:
http://git-scm.com/download/mac
Where it says: "You are downloading version 2.0.1 of Git for the Mac platform. This is the most recent maintained build for this platform. It was released 6 months ago, on 2014-06-29."
So that is an old version.

So going back to the first page, there are two more choices: a GUI client or Git via Git. The GUI client, GitHub for Mac, nowhere does it explain if it also contains Git itself and/or if it will upgrade my version to the newest. Or if it will conflict with my current version.

So, Git via Git: like explained here,
http://git-scm.com/book/en/v2/Getting-Started-Installing-Git
at the bottom are instructions, but for me those are confusing as well.

Last, on some websites people explain they use Homebrew. But that's yet another piece of code and dependency I have to install. And about which I read conflicting opinions (some people warning it messes up my system, etc).

I just want a simple method which allows me to cleanly update my Git version. I don't understand why it's so difficult.