Multiple checkouts of the same repository

Dear git people,

Maybe this is common knowledge, but I thought I should mention it in case it isn't. I had a git repository in a directory A and I wanted to check out a branch of the repository to a different directory B. So I created B/.git and filled it with symlinks pointing to the files in A/.git, except for index and HEAD because those need to be different for each checkout; then I ran git-checkout <branch> to fill B. Now I can view and edit each checkout independently, but they are backed by the same set of objects and refs. However, I must remember to commit to each branch only through the checkout whose HEAD is linked to it, otherwise that checkout won't get updated.

Matt