Homebrew formula for installing the official Rust nightly binary build. Useful because: (1) the `rust.rb` formula in Homebrew does not currently install Crate, and (2) the official binary `.pkg` pollutes `/usr/local`. This formula respects Homebrew's installation directory.

rust_nightly.rb

class RustNightly < Formula

  url "https://static.rust-lang.org/dist/rust-nightly-x86_64-apple-darwin.pkg", using: :nounzip
  homepage "http://www.rust-lang.org"
  sha1 ""

  version Date.today.to_s

  def install
    system "pkgutil --expand rust-nightly-x86_64-apple-darwin.pkg rn"
    Dir.mkdir "output"
    Dir.chdir "output"
    system "tar xf ../rn/rust.pkg/Payload"
    lib_path_update("bin/rustc")
    lib_path_update("bin/rustdoc")
    prefix.install Dir["*"]
  end

  private

  def otool(path)
    lines = %x[otool -L #{path}].split /\n/
    lines[1..-1].map do |line|
      line.
        strip.
        gsub(/ \(compatibility version.*$/, '')
    end
  end

  def install_name_tool(path, old)
    pattern = 'x86_64-apple-darwin/stage1/lib/rustlib/x86_64-apple-darwin'
    if path.match(pattern)
      new = old.gsub(pattern, prefix)
      system("install_name_tool -change '#{old}' '#{new}' '#{path}'")
    end
  end

  def lib_path_update(binary)
    otool(binary).each do |current_lib_path|
      install_name_tool(binary, current_lib_path)
    end
  end

end