Or you can add this to your .gitconfig on your computer. This file is usually found at ~/.gitconfig.
name = Your Name
email = firstname.lastname@example.org
lg = log --topo-order --all --graph --date=local --pretty=format:'%C(green)%h%C(reset) %><(55,trunc)%s%C(red)%d%C(reset) %C(blue)[%an]%C(reset) %C(yellow)%ad%C(reset)%n'
Now you can run git lg and see a much nicer tree. Here's what it looks like when you use the custom git lg command instead of git log.
And here's what the old and ugly git log command looks like: