CAVEAT: This works for me on Linux Mint 17.3. YMMV, caveat emptor, etc.
If this looks like (like maybe it should be a bash-git theme), hey, I agree with you, but I spent as many hours struggling with doing this "the right way" as I'm willing to put in.
Some of the custom characters come from Font Awesome. You should install the Font Awesome font into your system to use them. They may have what appears to be odd extra-spacing owing to the fact that Font Awesome is not fixed pitch, but Terminal expects it to be.
Add the following three lines to your .bashrc:
source ~/.bash-git-prompt/gitprompt.sh