Jon Loeliger [off-list ref] writes:
I have done this style of "update-index on more-or-less OK
files in order to clear up the diff. And it is also in that
time frame that I start feeling that certain changes belong
to "one commit" or another. The result is, I want to then
pick the parts that get committed together. But _really_
being certain exactly which files, and _only_ those files,
will really be committed is tough.
$ git diff --cached
would help. If you are _only_ comitting either all changes or no
change per path, 'git diff --cached --name-status' would be
sufficient.