way to automatically add untracked files?

One thing I often want to do is git-add all untracked files, and also automatically git-rm all "disappeared" files (I keep my .gitignore files well maintained, so the list of adding/missing files shown by git status is almost always correct). At the same time, I usually want to do "git add -u" to git-add modified files.

One way to do this seems to be just "git add .", but I'm always slightly nervous using it because it sits there and churns the disk for an awful long time (whereas "git status" is instantaneous). Is this the right thing to do? Is there something funny causing the churning?

Thanks,

-Miles