brew update is stuck

There is no output, no errors, no nothing. It just sits there.

Maybe related to this, who knows? https://github.com/Homebrew/brew/issues/3285

So I reinstalled brew.

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"

But then the install process is stuck at this line

==> /usr/bin/sudo /usr/bin/xcode-select --switch /Library/Developer/CommandLineTools

After some googling, apparently it’s caused by some combination of osx and xcode, see here: https://github.com/nodejs/node-gyp/issues/569. So I ran the following to fix the issue.

sudo xcode-select -s /Applications/Xcode.app/Contents/Developer

But then after Ctrl-C and reinstall brew, I got stuck at another line, seems like it did a git reset HEAD but stuck right after.

I tried a few other things but nothing could pass that point. Then just random guessing I checked my Software Update, and saw a 5Gb osx update sitting there waiting, I was like, why not?

So update osx, reboot, then magically brew starts working. =)