Yosemite uses Ruby 2.0 where as my previously installed Homebrew was set to use 1.8. I did an upgrade from Mavericks to Yosemite just last week, but it was today that I set out using brew commands and realized, oh no! But I have a 2 minute fix that works just fine.
Step 1
Change the first line of brew.rb (located in /usr/local/Library) to this:
#!/usr/bin/ruby -W0
Step 2
Follow these commands in order:
cd `brew --prefix` git clean -f git reset --hard FETCH_HEAD git clean -fd brew update
And you are done. Finally, you should see something like this if all went well.
Updated Homebrew from 3315455f to 3315455f.
Thanks for checking out Mr. Geek. Adios.