The cobra generator can't add commands when a project is accessed via a symlink

[mikolysz]

Overview:

When your working directory is set to a project directory but the path contains a symlink, cobra add complains that your project isn't in the gopath even though it really is.

steps to reproduce:

vagrant@vagrant-ubuntu-trusty-64:~$ cobra init github.com/miki123211/symlinks
Your Cobra application is ready at
/vagrant/go/src/github.com/miki123211/symlinks.

Give it a try by going there and running `go run main.go`.
Add commands to it by running `cobra add [cmdname]`.
vagrant@vagrant-ubuntu-trusty-64:~$ cd /vagrant/go/src/github.com/miki123211/sy
mlinks/
vagrant@vagrant-ubuntu-trusty-64:/vagrant/go/src/github.com/miki123211/symlinks
$ cobra add thisWorks
thisWorks created at /vagrant/go/src/github.com/miki123211/symlinks/cmd/thisWork
s.go
vagrant@vagrant-ubuntu-trusty-64:/vagrant/go/src/github.com/miki123211/symlinks
$ ln -s . ~/proj
vagrant@vagrant-ubuntu-trusty-64:/vagrant/go/src/github.com/miki123211/symlinks
$ cd ~/proj
vagrant@vagrant-ubuntu-trusty-64:~/proj$ cobra add thisshouldWorkButItDoesNot
Error: Cobra supports project only within $GOPATH: Rel: can't make /home/vagrant
/proj relative to
vagrant@vagrant-ubuntu-trusty-64:~/proj$

Expected output:

thisShouldWorkButItDoesNot created at /vagrant/go/src/github.com/miki123211/symlinks/cmd/thisShouldWorkButItDoesNot.go