replace brew-cask.rb subcommand with bash shim

The `brew-cask` shim finds and executes `lib/brew-cask-cmd.rb`,
but only if Ruby 2.0+ is found.

bin/brew-cask

@@ -0,0 +1,169 @@
+#!/bin/bash
+#
+# brew-cask
+#
+# bash shim to invoke brew-cask-cmd.rb
+#
+
+###
+### settings
+###
+
+set -e
+set -o pipefail
+set +o histexpand
+set -o nounset
+shopt -s nocasematch
+shopt -s nullglob
+shopt -s dotglob
+
+###
+### functions
+###
+
+warn () {
+    local message="$@"
+    message="${message//\\t/$'\011'}"
+    message="${message//\\n/$'\012'}"
+    message="${message%"${message##*[![:space:]]}"}"
+    printf "%s\n" "$message" 1>&2
+}
+
+die () {
+    warn "$@"
+    exit 1
+}
+
+resolve_dir () {
+    local resolved="$(for dir; do cd "$dir"; done && /bin/pwd -P)"
+    if [[ -d "$resolved" ]]; then
+        printf "%s" "$resolved"
+    else
+        die "cannot resolve: '$@'"
+    fi
+}
+
+ensure_dir () {
+    local dir="$1"
+    local message
+    shift
+
+    if [ "$#" -gt 0 ]; then
+        message="$@"
+    else
+        message="brew-cask: no such directory: '$dir'"
+    fi
+    if ! [[ -d "$dir" ]]; then
+        die "$message"
+    fi
+}
+
+ensure_file () {
+    local file="$1"
+    local message
+    shift
+
+    if [ "$#" -gt 0 ]; then
+        message="$@"
+    else
+        message="brew-cask: no such file: '$file'"
+    fi
+    if ! [[ -f "$file" ]]; then
+        die "$message"
+    fi
+}
+
+ensure_executable () {
+    local executable="$1"
+    local message
+    shift
+
+    if [ "$#" -gt 0 ]; then
+        message="$@"
+    else
+        message="brew-cask: no such executable: '$executable'"
+    fi
+    if ! [[ -f "$executable" ]] || ! [[ -x "$executable" ]]; then
+        die "$message"
+    fi
+}
+
+find_ruby_2_plus () {
+    declare -a rubies
+    local favorite_ruby="/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby"
+    local version_str
+
+    if [[ -x "$favorite_ruby" ]]; then
+        printf "%s" "$favorite_ruby"
+    else
+        IFS=$'\n' rubies=( $(/usr/bin/type -aP ruby)   \
+                           "/usr/local/bin/ruby"       \
+                           "$(brew --prefix 2>/dev/null)/bin/ruby" )
+        for ruby in "${rubies[@]}"; do
+            version_str="$("$ruby" --version 2>/dev/null)"
+            if [[ "$version_str" =~ ^ruby.2 ]]; then
+                printf "%s" "$ruby"
+                break
+            fi
+        done
+    fi
+}
+
+###
+### main
+###
+
+_brew_cask () {
+    local script_dir
+    local symlink_target
+    local symlink_target_dir
+    local brewcask_lib_dir
+    local brewcask_command
+    local interpreter
+    declare -a ruby_opts
+
+    ruby_opts=( "-W0" "-EUTF-8:UTF-8" )
+
+    script_dir="$(resolve_dir "${0%/*}")"
+    ensure_dir "$script_dir" \
+               "brew-cask: could not resolve script directory"
+
+    # return "." in case we are not a link
+    symlink_target="$(/usr/bin/readlink "$0" || echo ".")"
+
+    # redefine script_dir because we are likely to be a relative link
+    symlink_target_dir="$(/usr/bin/dirname "$symlink_target")"
+    script_dir="$(resolve_dir "$script_dir" "$symlink_target_dir")"
+    ensure_dir "$script_dir" \
+               "brew-cask: could not resolve script directory"
+
+    # The Homebrew install process replaces the lib element below with rubylib
+    brewcask_lib_dir="$(resolve_dir "$script_dir"/../lib)"
+    ensure_dir "$brewcask_lib_dir" \
+               "brew-cask: could not resolve homebrew-cask library directory"
+
+    brewcask_command="$brewcask_lib_dir/brew-cask-cmd.rb"
+    ensure_file "$brewcask_command" \
+                "brew-cask: could not find brew-cask-cmd.rb in '$brewcask_lib_dir'"
+
+    interpreter="$(find_ruby_2_plus)"
+    ensure_executable "$interpreter" \
+                      "brew-cask: could not find Ruby 2.0 or greater.  Try 'brew install ruby'."
+
+    exec "$interpreter" "${ruby_opts[@]}" "$brewcask_command" "${@}"
+}
+
+###
+### initialization
+###
+
+unset GEM_HOME
+unset GEM_PATH
+
+###
+### dispatch
+###
+
+_brew_cask "${@:-}"
+
+#

brew-cask.rb

@@ -14,9 +14,9 @@ class BrewCask < Formula
   def install
     man1.install 'doc/man/brew-cask.1'
     prefix.install 'lib' => 'rubylib'
-    inreplace 'bin/brew-cask.rb', '/lib', '/rubylib'
+    inreplace 'bin/brew-cask', '/lib', '/rubylib'
 
     prefix.install 'Casks', 'bin'
-    (bin+'brew-cask.rb').chmod 0755
+    (bin+'brew-cask').chmod 0755
   end
 end

doc/hacking.md

@@ -125,7 +125,7 @@ alternate version of the `brew-cask` subcommand, by invoking `brew cask`
 with fully-qualified paths, like this:
 
 ```bash
-$ HOMEBREW_BREW_FILE=/usr/local/bin/brew /System/Library/Frameworks/Ruby.framework/Versions/Current/usr/bin/ruby /usr/local/Library/brew.rb /usr/local/bin/brew-cask.rb help
+$ HOMEBREW_BREW_FILE=/usr/local/bin/brew /System/Library/Frameworks/Ruby.framework/Versions/Current/usr/bin/ruby /usr/local/Library/brew.rb /usr/local/Library/Taps/caskroom/homebrew-cask/bin/brew-cask-cmd.rb help
 ```
 
 #### Forcing a Specific Homebrew-cask Subcommand

lib/brew-cask-cmd.rb

@@ -0,0 +1,16 @@
+#!/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby -W0 -EUTF-8:UTF-8
+# encoding: UTF-8
+
+require 'pathname'
+
+# todo remove internal Homebrew dependencies and remove this line
+$LOAD_PATH.unshift(File.expand_path('../homebrew-fork/Library/Homebrew', Pathname.new(__FILE__).realpath))
+$LOAD_PATH.unshift(File.expand_path('..', Pathname.new(__FILE__).realpath))
+
+# todo remove internal Homebrew dependencies and remove this line
+require 'global'
+
+require 'cask'
+
+Cask::CLI.process(ARGV)
+exit 0