Hi,
Allowing what Mark wants without any explicit user customization will be a
disaster to the end user experience.
If the ability to commit a currently untracked file/tree whilst
preserving the index is really worth having (and that's debatable, as
the git user community has survived until now without that capability)
then another option (say, -O) could be added to git-commit that does
what -o does but allows untracked files/trees to be specified - that
way, the current behaviour would remain unchanged and the above
mentioned disaster averted.
Cheers,
Mark