I believe there's a flag to `commit` that effectively does `add .` first.

I disagree with your statistic though - I can't tell you what the flag is precisely because it's almost never what I want; so I never use it and haven't learnt it.

I think these things just vary with workflow.

Just for completeness sake, the command to do that would be

  git commit -a

It does an implicit git add -u (which does not add new files not yet part of the repo)

I record my uses of each command and the current counts are the following (g is my shell alias for git):

    161 g cap      # commit --patch --amend
    170 g adu      # add -u
    205 g add -p   # add --patch
    277 g ci       # commit -a
    484 g cip      # commit --patch

At least, I use it a lot. ;)

So you disagree based on your personal experience? That is fine. I base my observation on what the people around me were using in various environments, so I am actually fairly confident that this can be generalized. This is the best I can do unless someone makes some representative statistics over a broad user base.