`Gem.unpack` extracts gems so able to execute

Creates simple bin stubs to load the extracted executable files.
After only extracted under `gems` directory, the gems are considered
installed but the executable scripts are not found.
Also the second argument is now the parent of the previous second and
third arguments.

common.mk

@@ -1360,13 +1360,11 @@ extract-gems$(gnumake:yes=-nongnumake): PHONY
 	$(ECHO) Extracting bundled gem files...
 	$(Q) $(RUNRUBY) -C "$(srcdir)" \
 	    -Itool -rfileutils -rgem-unpack -answ \
-	    -e 'BEGIN {FileUtils.mkdir_p(d = ".bundle/gems")}' \
-	    -e 'BEGIN {FileUtils.mkdir_p(s = ".bundle/specifications")}' \
+	    -e 'BEGIN {d = ".bundle/gems"}' \
 	    -e 'gem, ver = *$$F' \
 	    -e 'next if !ver or /^#/=~gem' \
 	    -e 'g = "#{gem}-#{ver}"' \
-	    -e 'File.directory?("#{d}/#{g}") or Gem.unpack("gems/#{g}.gem", d, s)' \
-	    -e 'FileUtils.rm_rf("#{d}/#{g}/.github")' \
+	    -e 'File.directory?("#{d}/#{g}") or Gem.unpack("gems/#{g}.gem", ".bundle")' \
 	    gems/bundled_gems
 
 update-bundled_gems: PHONY

defs/gmake.mk

@@ -298,8 +298,7 @@ extract-gems: | $(patsubst %,.bundle/gems/%,$(bundled-gems))
 	$(ECHO) Extracting bundle gem $*...
 	$(Q) $(BASERUBY) -C "$(srcdir)" \
 	    -Itool -rgem-unpack \
-	    -e 'Gem.unpack("gems/$(@F).gem", ".bundle/gems", ".bundle/specifications")'
-	$(RMALL) "$(srcdir)/$(@:.gem=)/".git*
+	    -e 'Gem.unpack("gems/$(@F).gem", ".bundle")'
 
 $(srcdir)/.bundle/gems:
 	$(MAKEDIRS) $@

tool/gem-unpack.rb

@@ -5,22 +5,30 @@ require 'rubygems/package'
 # This library is used by "make extract-gems" to
 # unpack bundled gem files.
 
-def Gem.unpack(file, dir = nil, spec_dir = nil)
+def Gem.unpack(file, dir = ".")
   pkg = Gem::Package.new(file)
   spec = pkg.spec
   target = spec.full_name
-  target = File.join(dir, target) if dir
-  pkg.extract_files target
-  if spec.extensions.empty?
-    spec_dir ||= target
-  else
-    spec_dir = target
-  end
-  FileUtils.mkdir_p(spec_dir)
-  File.binwrite(File.join(spec_dir, "#{spec.name}-#{spec.version}.gemspec"), spec.to_ruby)
+  Gem.ensure_gem_subdirectories(dir)
+  gem_dir = File.join(dir, "gems", target)
+  pkg.extract_files gem_dir
+  spec_dir = spec.extensions.empty? ? "specifications" : File.join("gems", target)
+  File.binwrite(File.join(dir, spec_dir, "#{target}.gemspec"), spec.to_ruby)
   unless spec.extensions.empty?
     spec.dependencies.clear
-    File.binwrite(File.join(spec_dir, ".bundled.#{spec.name}-#{spec.version}.gemspec"), spec.to_ruby)
+    File.binwrite(File.join(dir, spec_dir, ".bundled.#{target}.gemspec"), spec.to_ruby)
   end
+  if spec.bindir and spec.executables
+    bindir = File.join(dir, "bin")
+    Dir.mkdir(bindir) rescue nil
+    spec.executables.each do |exe|
+      File.open(File.join(bindir, exe), "wb", 0o777) {|f|
+        f.print "#!ruby\n",
+                %[load File.realpath("../gems/#{target}/#{spec.bindir}/#{exe}", __dir__)\n]
+      }
+    end
+  end
+  FileUtils.rm_rf(Dir.glob("#{gem_dir}/.git*"))
+
   puts "Unpacked #{file}"
 end