How do I do a git status so it doesn't display untracked files without using .gitignore? I want to get modification status information on tracked files only.

Use this:

git status -uno

which is equivalent to:

git status --untracked-files=no

It's a bit hidden in the manuals, but the manpage for status says "supports the same options as git-commit", so that's where you'd have to look.