It's taken me ages to work this out - and I know the instructions are patchy, and really are aimed at someone who is already familiar with setting up systems.
However - to tell the story.
I have tracked all over the many many pages already devoted to git, but could find nothing that told me definitively and simply how to update an existing site using git, or even create a new one using git, that I could then maintain with a simple
$ git pull
and will never be updating code or modifying modules etc. that I have to send anywhere else.
Finally - this is what I have
I have Git installed on my Windows XP machine. I don't use the GUI, just the Bash interface, which is almost the same as a normal Unix bash interface. cool.
I was already running a downloaded version of Drupal, but wanted to be able to maintain it with git, not doing the download, unpack, delete, overwrite, upgrade thing each time. Just for kicks really, and wanted to see if it could be done.
so here goes.
My existing install was in a directory called a-drupal, and my apache web server pointed to that.
My new install is in dru-project and now the apache web server points to that.
The users don't see any of that of course. Call your's what you like.
Upgrading or installing Drupal using git on Windows.