EDIT: Homebrew has fixed this: You should be able to just pull in the lates version of homebrew and be good to go. :)

OSX Yosemite breaks things. If you install the beta right now, you might notice that when you try to use homebrew, you'll get an error, much like this:

/usr/local/bin/brew: /usr/local/Library/brew.rb: /System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby: bad interpreter: No such file or directory /usr/local/bin/brew: line 23: /usr/local/Library/brew.rb: Undefined error: 0

You can easily fix this by editing the ruby path in brew.rb file.

Open up /usr/local/Library/brew.rb, and change the version from 1.8 to current.

#!/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby -W0 

should become....

#!/System/Library/Frameworks/Ruby.framework/Versions/current/usr/bin/ruby -W0 

Save the file, and walla! You should be gold. :)