Git on mac, how to view files currently in GIT?

I setup a file extension to be ignored, how can I tell if it was added to git?

I use git add -A to bulk add files.

btw, what popular GUI tools are used for diff's?

git status before you commit everything (as in just after you git add) will show you if your files with the extension you want ignored have been added.

I personally prefer to just use git diff but that's not a GUI. People seem to like Git-K. If I'm reviewing code, I love Github's diff tools. Allows me to look at differences between entire branches and comment on specific lines of code.