We are new to git, and I want to set a tag at the beginning of our repository.
Our production code is the same as the beginning repository, but we've made commits since then.
A tag at the beginning would allow us to "roll back" production to a known, stable state.
So how to add a tag to an arbitrary, older commit?
git tag -a v1.2 9fceb02 -m "Message here"
9fceb02 is the beginning part of the commit id.
You can then push them up using
git push --tags origin master
You can do
git log to show all the commit id's in your current branch.
There is also a good chapter on tagging in the Pro Git book.