If I'm switching between a couple projects a lot (which I have been this week) I try to run git status whenever I start working in a project again. Usually, it's just the files I have failed to commit because I was working on something "really quick" but today I was presented with the following:

# On branch master
# Your branch is ahead of 'origin/master' by 3 commits.
#

I was of course confused because I didn't remember what it was that I changed but didn't commit. In order to check this I ran the following command which
gave me exactly what I was looking for:

git log origin/master..HEAD