Use the -p (--patch) flag, it works wonderfully for selectively marking blocks for staging (git add -p), and selectively checking out changed files with (git checkout -p).
My experience is that you'll quickly get burned if you do this for the use case the OP mentioned. The goal is to keep different settings for a development environment, not to just temporarily avoid committing. One day, you'll inevitably forget and accidentally commit and push the changes you've been carefully avoiding.
I've not had that experience at all. For the times you know it would be tedious to add/ignore all diffs manually, you can just use the 'a' or 'd' commands to add or ignore for the remainder of the current file. I much prefer using 'add -p' every single time I commit.