add "rscons" binary - close #24

bin/rscons

@@ -0,0 +1,3 @@
+require "rscons/cli"
+
+Rscons::Cli.run(ARGV)

lib/rscons/cli.rb

@@ -0,0 +1,78 @@
+require "rscons"
+require "optparse"
+
+module Rscons
+  # Command-Line Interface functionality.
+  module Cli
+
+    # Default files to look for to execute if none specified.
+    DEFAULT_RSCONSFILES = %w[Rsconsfile Rsconsfile.rb]
+
+    class << self
+
+      # Run the Rscons CLI.
+      #
+      # @param argv [Array]
+      #   Command-line parameters.
+      #
+      # @return [void]
+      def run(argv)
+        argv = argv.dup
+        rsconsfile = nil
+
+        OptionParser.new do |opts|
+          opts.banner = "Usage: #{$0} [options]"
+
+          opts.separator ""
+          opts.separator "Options:"
+
+          opts.on("-c", "--clean", "Perform clean operation") do
+            Rscons.clean
+            exit 0
+          end
+
+          opts.on("-f FILE", "Execute FILE (default Rsconsfile)") do |f|
+            rsconsfile = f
+          end
+
+          opts.on_tail("--version", "Show version") do
+            puts "Rscons version #{Rscons::VERSION}"
+            exit 0
+          end
+
+          opts.on_tail("-h", "--help", "Show this help.") do
+            puts opts
+            exit 0
+          end
+
+        end.parse!(argv)
+
+        if rsconsfile
+          unless File.exists?(rsconsfile)
+            $stderr.puts "Cannot read #{rsconsfile}"
+            exit 1
+          end
+        else
+          rsconsfile = DEFAULT_RSCONSFILES.find do |f|
+            File.exists?(f)
+          end
+          unless rsconsfile
+            $stderr.puts "Could not find the Rsconsfile to execute."
+            $stderr.puts "Looked in: [#{DEFAULT_RSCONSFILES.join(", ")}]"
+            exit 1
+          end
+        end
+
+        begin
+          load rsconsfile
+        rescue Rscons::BuildError => e
+          $stderr.puts e.message
+          exit 1
+        end
+
+        exit 0
+      end
+
+    end
+  end
+end