RFC: display dirty submodule working directory in git gui and gitk

[Jens Lehmann <Jens.Lehmann@web.de>]

Now that we have much better output when displaying diffs of
submodules in git gui and gitk (many thanks to all involved!),
another usability issue shows up: A dirty working directory of
a submodule isn't visible in git gui or gitk.

So you might think a "submodule update" would be ok - as you
see no changes - just too see it fail because the submodules
working directory is dirty.

Or - even worse - you /think/ you committed your changes in
a submodule while you didn't. That can lead to 'interesting'
problems which can be pretty hard to diagnose (like breaking
builds on other peoples machines).


A possible solution could look like this:

AFAICS, git gui and gitk use "git diff-files" both to get the
file names of unstaged local changes and to later display the
actual differences.

If they could tell the diff core to also check the submodule
working directories and to output an extra line - maybe
something like "Submodule <name> contains uncommitted local
changes" - when a submodules working directory is dirty,
git gui and gitk could show the submodules state adequately.


What do you think about this approach?