Sublime Text CLI doesn't work after upgrading to El Capitan

I suffered this problem on my new laptop: a staple of opening files in sublime from the command line stopped working:
$ subl -n /tmp/foo.sh

I tracked it down to a few things:

• it worked correctly in a new shell
• it was only broken inside tmux

Searching yielded lots of half answers that were confusing about reattach-to-user-namespace. My solution:

• brew install reattach-to-user-namespace
• alias subl='reattach-to-user-namespace subl'

Assuming you have your subl symlink set up and in your path,  these changes will make it work from within tmux.