Any way to ignore a change to a tracked file when committing/merging?

I've got a problem, or maybe annoyance is more the proper term, that I haven't seen solved by any SCM system (at least not to my knowledge). Basically, I may make some changes, e.g. to a Makefile or somesuch, that I want to ignore when looking at what's changed from the repository. The only problem is, the file I've modified is already under version control, so .gitignore doesn't do anything.

Now, I can commit it, so it will stop bugging me, but then when I push out it will include that change, unless I back it out. This is a change that I don't want propagated anywhere else, because it's specific to my machine or development sandbox.

Is there any way to do this? I'd really love to use git-commit -a in this situation, and I could hack up a script to undo my change, run git-commit -a, and reapply the change, but makes me a bit squirmy. If I could put something in a .git config file to say "commit 237ab should not be propagated under any circumstances", that would be fantastic.

-Dave Watson