If you're using Homebrew[1], then it's simply a case of:
$ brew install --HEAD vim
[1] http://brew.sh
$ brew install --HEAD vim
[1] http://brew.sh
cd /usr/local/Cellar/vim/HEAD/share/vim/vim80/compiler; chmod 644 *.vim README.txt
-bash: cd: /usr/local/Cellar/vim/HEAD/share/vim/vim80/compiler: No such file or directory
chmod: *.vim: No such file or directory
chmod: README.txt: No such file or directory
Eh..I'll probably wait a little bit longer.It's happily just compiled and installed for me.
$ brew update && brew upgrade vim --HEAD
I've since put Windows 10 on my MBPr (performs so much goddamned faster, Ivy Bridge era /w Intel GPU only, 8gb of RAM, decentish SSD for that generation), and use msys2 to fill that gap.
Disclaimer: My company Exelion hosts the msys2 mirror because their project is so important to the Windows community, and Sourceforge was having serious issues at the time. Well worth spending a dedi on them to keep the project going, imo.