git (commit|tag) atomicity

Hi,
I don't know a lot about git - I use it as a tool behind
http://cyber-dojo.com
which is an online coding dojo server.
I have a quick question...
If I do a
   git commit ....
in one thread and a
   git tag | sort -g
in another thread is the output of the git tag guaranteed to be atomic?
That is, the output will be from before the git commit or after it but
not a mixture?
Logically, I assume so but cannot find anything definitive on google
or in my git books or from the lips of my friends.
Thanks for any help
Jon Jagger