# まずはアップデートして
% brew update
Updated 1 tap (homebrew/core).
No changes to formulae.
# お医者さんで健康か確認する
% brew doctor
Your system is ready to brew.
# SourceTreeをインストールする
% brew install sourcetree
Updating Homebrew...
==> Auto-updated Homebrew!
Updated 1 tap (homebrew/cask).
==> Updated Casks
Updated 1 cask.
==> Downloading https://product-downloads.atlassian.com/software/sourcetree/ga/Sourcetree_4.0.2_236.zip
######################################################################## 100.0%
==> Installing Cask sourcetree
==> Moving App 'Sourcetree.app' to '/Applications/Sourcetree.app'.
==> Linking Binary 'stree' to '/usr/local/bin/stree'.
🍺 sourcetree was successfully installed!