Downloader: Define per-class command line options

Move `Downloader::Unicode` specific options, and parse options after
the downloader specificier.

tool/downloader.rb

@@ -36,6 +36,12 @@ else
 end
 
 class Downloader
+  def self.find(dlname)
+    constants.find do |name|
+      return const_get(name) if dlname.casecmp(name.to_s) == 0
+    end
+  end
+
   def self.https=(https)
     @@https = https
   end
@@ -48,6 +54,10 @@ class Downloader
     @@https
   end
 
+  def self.get_option(argv, options)
+    false
+  end
+
   class GNU < self
     def self.download(name, *rest)
       if https?
@@ -78,6 +88,21 @@ class Downloader
     INDEX = {}  # cache index file information across files in the same directory
     UNICODE_PUBLIC = "https://www.unicode.org/Public/"
 
+    def self.get_option(argv, options)
+      case argv[0]
+      when '--unicode-beta'
+        options[:unicode_beta] = argv[1]
+        argv.shift(2)
+        true
+      when /\A--unicode-beta=(.*)/m
+        options[:unicode_beta] = $1
+        argv.shift
+        true
+      else
+        super
+      end
+    end
+
     def self.download(name, dir = nil, since = true, options = {})
       options = options.dup
       unicode_beta = options.delete(:unicode_beta)
@@ -173,7 +198,6 @@ class Downloader
     options = options.dup
     url = URI(url)
     dryrun = options.delete(:dryrun)
-    options.delete(:unicode_beta) # just to be on the safe side for gems and gcc
 
     if name
       file = Pathname.new(under(dir, name))
@@ -351,7 +375,25 @@ Downloader.https = https.freeze
 if $0 == __FILE__
   since = true
   options = {}
+  dl = nil
+  (args = []).singleton_class.__send__(:define_method, :downloader?) do |arg|
+    !dl and args.empty? and (dl = Downloader.find(arg))
+  end
   until ARGV.empty?
+    if ARGV[0] == '--'
+      ARGV.shift
+      break if ARGV.empty?
+      ARGV.shift if args.downloader? ARGV[0]
+      args.concat(ARGV)
+      break
+    end
+
+    if dl and dl.get_option(ARGV, options)
+      # the downloader dealt with the arguments, and should be removed
+      # from ARGV.
+      next
+    end
+
     case ARGV[0]
     when '-d'
       destdir = ARGV[1]
@@ -370,26 +412,18 @@ if $0 == __FILE__
     when '--cache-dir'
       options[:cache_dir] = ARGV[1]
       ARGV.shift
-    when '--unicode-beta'
-      options[:unicode_beta] = ARGV[1]
-      ARGV.shift
     when /\A--cache-dir=(.*)/m
       options[:cache_dir] = $1
     when /\A-/
       abort "#{$0}: unknown option #{ARGV[0]}"
     else
-      break
+      args << ARGV[0] unless args.downloader? ARGV[0]
     end
     ARGV.shift
   end
-  dl = Downloader.constants.find do |name|
-    ARGV[0].casecmp(name.to_s) == 0
-  end unless ARGV.empty?
   $VERBOSE = true
   if dl
-    dl = Downloader.const_get(dl)
-    ARGV.shift
-    ARGV.each do |name|
+    args.each do |name|
       dir = destdir
       if prefix
         name = name.sub(/\A\.\//, '')
@@ -409,7 +443,7 @@ if $0 == __FILE__
       dl.download(name, dir, since, options)
     end
   else
-    abort "usage: #{$0} url name" unless ARGV.size == 2
-    Downloader.download(ARGV[0], ARGV[1], destdir, since, options)
+    abort "usage: #{$0} url name" unless args.size == 2
+    Downloader.download(args[0], args[1], destdir, since, options)
   end
 end