MacOSX で brew update が error の時に、試すこと

Overview

brew updateしようとしたら、以下のようにエラーがでたときに試したこと。

$ brew update
warning: unable to unlink .yardopts: Permission denied
warning: unable to unlink CONTRIBUTING.md: Permission denied
warning: unable to unlink SUPPORTERS.md: Permission denied
fatal: cannot create directory at '.github': Permission denied
Error: Failure while executing: git pull --quiet origin refs/heads/master:refs/remotes/origin/master

$ sudo brew update
Password:
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- mach (LoadError)
    from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /usr/local/Library/Homebrew/extend/pathname.rb:2:in `<top (required)>'
    from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /usr/local/Library/Homebrew/global.rb:3:in `<top (required)>'
    from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require'
    from /usr/local/Library/brew.rb:15:in `<main>'

解決策

$ cd /usr/local
$ git status
汚れている
$ git reset --hard && git clean -df
HEAD is now at 3cc2026 lzlib: update 1.7 bottle.
$ sudo brew update

で、その後、本当はやりたかった

$ brew install mosquitto

を正しく行うことができましたとさ。

ちなみに、brew updateをしなければと思ったのは以下のエラーが出たため

$ brew install mosquitto
..snip..
==> Installing mosquitto dependency: libwebsockets
==> Downloading http://git.libwebsockets.org/cgi-bin/cgit/libwebsockets/snapshot/libwebsockets-1.4-chrome43-firefox-36.tar.gz
######################################################################## 100.0%
curl: (56) SSLRead() return error -9806
Error: Failed to download resource "libwebsockets"
Download failed: http://git.libwebsockets.org/cgi-bin/cgit/libwebsockets/snapshot/libwebsockets-1.4-chrome43-firefox-36.tar.gz