Branch completion shouldn't consider deleted branches

[mymikemiller]

After following the steps here for adding git_completion to Mac, when I type "git checkout mm-" and press tab, I see all the branches that ever started with mm-, including the ones I have deleted. Is this expected? Would be nice if completion would only work for the branches that show up when I do "git branch".

I also see other people's branches and I'd prefer not to, but that's not as much of an issue since we prefix our branch names with a personal identifier (mm- for me)