git for versioning

[Rustom Mody]

I am trying to use git for maintaining multiple versions of a
document.  Was wondering what is the way (if any)?

Say I have a base document: foo

And then there are three versions -- AlbertFoo, BethFoo and CarolFoo
-- all of which are Foo + some stuff for that specific context.
Now working on these versions is easy -- just check out that version
and work on it.

But how do I work on the base and have it push (yeah, that's not
exactly the word) its changes through the (branches for) Albert, Beth
and Foo?

I tried to study rebase for this but I guess its not the thing I want.