Väinö Järvelä [off-list ref] writes:
The way I see the flag used is: A user runs "git status", sees that
there is too much untracked files and not enough scrollback, so he
runs "git status --only-tracked" to filter the results.
Why?
Just set up .gitignore once then (1) you do not have to worry
about them ever again, and (2) you _will_ still be able to
notice if you accidentally added more cruft, or more
importantly, if you forgot to tell an important file to git.
I think the latter is more important point. If you train a
naive user to use --only-tracked to ignore "Untracked" list, you
are doing him or her a great disservice. Mistake to forget "git
add" a new file before commiting will bound to happen.