Headed into my HomeBrew installation this morning to upgrade a few packages, but noticed that it just did not work on Sierra.

After a while of trying to upgrade the install, I ended up just doing the install from http://brew.sh/ again.

So this command:

/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

After which Homebrew worked like a charm, then while updating I noticed that all my packages have not be linked anymore.

So I found this command to run that will unlink all the packages in one shot:

brew list -1 | while read line; do brew unlink $line; brew unlink $line; done  

And this command that will link them all again with one command:

brew list -1 | while read line; do brew link $line; brew link $line; done  

After which I was able to run brew upgrade again :), enjoy!

--

Joseph Hurtado reported back in the comments that he still had an ownership issue where he still needed to run the following command:

sudo chown -R $(whoami) /usr/local/opt  

In case anyone runs into something similar.