Example ~/.gitconfig is given below. In it, I define a simple alias that will print a nice log graph, "logtree". "logtree" is invoked from the commandline as "git logtree". Arguments are passed, so I can do "git logtree --oneline" and get the expected result.
[user]
name = "Stephen Rosen"
email = "sirosen@uchicago.edu"
[alias]
logtree = "log --graph --decorate --all"
[push]