Added rpg-parse-gemfile command

.gitignore

@@ -39,6 +39,7 @@ rpg-resolve.html
 rpg-status.html
 rpg-package-install
 rpg-package-register
+rpg-parse-gemfile
 rpg-parse-package-list
 rpg-solve
 rpg-unpack

Makefile

@@ -28,7 +28,7 @@ PROGRAMPROGRAMS = \
 	rpg-outdated rpg-package-list rpg-package-register rpg-package-install \
 	rpg-unpack rpg-package-spec rpg-parse-index rpg-shit-list \
 	rpg-prepare rpg-complete rpg-help rpg-package-index rpg-dependencies \
-	rpg-leaves rpg-manifest rpg-solve rpg-diff
+	rpg-leaves rpg-manifest rpg-solve rpg-diff rpg-parse-gemfile
 
 DEADPROGRAMS = \
 	rpg-update rpg-status rpg-parse-package-list rpg-version-test

rpg-parse-gemfile.rb

@@ -0,0 +1,108 @@
+#!/usr/bin/env ruby
+# The `rpg-parse-gemfile` program reads a Bundler Gemfile and writes a
+# list of packages on standard output suitable for feeding to `rpg-install`.
+#
+# Usage
+# -----
+#
+# Given a project with a Gemfile, it is possible to install its dependencies
+# by running:
+#
+#     rpg install $(rpg parse-gemfile /path/to/Gemfile)
+#
+# Caveats
+# -------
+#
+# At this time only top-level gem statements are actually supported.
+# All options are ignored. All groups other than the top-level group are
+# ignored. All other statements are ignored.
+#
+# Bundler uses dependency declarations in all groups when resolving
+# dependencies, even in groups that are not being installed.
+# See http://yehudakatz.com/2010/05/09/the-how-and-why-of-bundler-groups/,
+# section "Consistency". This may render a Gemfile unresolvable if, for
+# example, the test group specifies conflicting or broken dependencies, even
+# for users who don't want to install the test group. rpg ignores all groups
+# that are not being installed during dependency resolution. As a consequence,
+# rpg and Bundler may install different sets of packages from the same Gemfile.
+USAGE = <<BANNER
+Usage: rpg-parse-gemfile [PATH]
+Convert Bundler Gemfile to a list of packages suitable for installation.
+
+Reads a Gemfile located at specified PATH, or standard input, and writes
+a list of packages suitable for feeding to rpg-install on standard output.
+
+Try: rpg install $(rpg parse-gemfile /path/to/Gemfile)
+BANNER
+
+if ARGV.include?('--help') || ARGV.length > 1 || ARGV.empty? && STDIN.tty?
+  puts USAGE
+  exit 2
+end
+
+class GemfileParser
+  def initialize
+    @packages = []
+  end
+
+  def parse(gemfile_text, file=nil)
+    eval(gemfile_text, nil, file)
+  end
+
+  def method_missing(name, *args)
+    #puts "Ignoring #{name}"
+  end
+
+  def gem(name, *args)
+    unless args.first.is_a?(Hash)
+      version = args.shift
+    end
+    options = args.shift || {}
+    @packages << {
+      :name => name, :version => version, :options => options,
+      :group => @in_group,
+    }
+  end
+
+  def group(name)
+    if @in_group
+      raise ArgumentError, 'Nested groups are not supported'
+    end
+    @in_group = name
+    yield
+    @in_group = nil
+  end
+
+  def print
+    @packages.each do |package|
+      next if package[:group]
+      version_op, version_value = canonicalize_version(package[:version])
+      puts "#{package[:name]} #{version_op} #{version_value}"
+    end
+  end
+
+  def canonicalize_version(version)
+    if version.nil?
+      return ['>=', '0']
+    end
+    unless version =~ /^([>=~]*)(\d.+)$/
+      raise ArgumentError, "Invalid version specification: #{version}"
+    end
+    op, value = $1, $2
+    if op.empty?
+      op = '='
+    end
+    return [op, value]
+  end
+end
+
+if (file = ARGV.shift) && file != '-'
+  text = File.read(file)
+else
+  file = '<stdin>'
+  text = STDIN.read
+end
+
+parser = GemfileParser.new
+parser.parse(text, file)
+parser.print