```ruby
class Carthage < Formula
  desc "Decentralized dependency manager for Cocoa"
  homepage "https://github.com/Carthage/Carthage"
  head "https://github.com/jdhealy/Carthage.git",
      :branch => 'fix-git-ls-tree',
      :revision => 'dcfd2444176dd42da3f4877faf95f28e8488d268',
      :using => :git,
      :shallow => false

  depends_on :xcode => ["8.2", :build]

  def install
    system "make", "prefix_install", "PREFIX=#{prefix}"
    bash_completion.install "Source/Scripts/carthage-bash-completion" => "carthage"
    zsh_completion.install "Source/Scripts/carthage-zsh-completion" => "_carthage"
    fish_completion.install "Source/Scripts/carthage-fish-completion" => "carthage.fish"
  end

  test do
    (testpath/"Cartfile").write 'github "jspahrsummers/xcconfigs"'
    system bin/"carthage", "update"
  end
end
```

Remove `:branch`, actually use `:revision`.
user
```ruby
class Carthage < Formula
  desc "Decentralized dependency manager for Cocoa"
  homepage "https://github.com/Carthage/Carthage"
  head "https://github.com/jdhealy/Carthage.git",
      :revision => 'dcfd2444176dd42da3f4877faf95f28e8488d268',
      :using => :git,
      :shallow => false

  depends_on :xcode => ["8.2", :build]

  def install
    system "make", "prefix_install", "PREFIX=#{prefix}"
    bash_completion.install "Source/Scripts/carthage-bash-completion" => "carthage"
    zsh_completion.install "Source/Scripts/carthage-zsh-completion" => "_carthage"
    fish_completion.install "Source/Scripts/carthage-fish-completion" => "carthage.fish"
  end

  test do
    (testpath/"Cartfile").write 'github "jspahrsummers/xcconfigs"'
    system bin/"carthage", "update"
  end
end
```
assistant