When trying to git pull pkgsrc repo from GitHub I saw an SSL error:
user@host:~/opt/pkgsrc$ git pull
fatal: unable to access 'https://github.com/jsonn/pkgsrc.git/': SSL certificate problem: unable to get local issuer certificate
I tested this guide on Ubuntu 14.04 with Nix package manager.
Note: I was using a git version pulled in from Nix. The git from Ubuntu was working just fine.