Confirmation before clobbering; only grade certain students.

lib/kgrader/cli.rb

@@ -47,7 +47,10 @@ module KGrader
     end
 
     def clobber
-      # TODO: confirm
+      puts "clobbering means deleting local student repos and roster files"
+      print "are you sure? [y/N] "
+      abort "aborted" unless ['y', 'yes'].include? STDIN.gets.strip.downcase
+
       reset_jail
       reset_desk
     end

lib/kgrader/roster.rb

@@ -19,10 +19,6 @@ module KGrader
       @students ||= @fs.load(rosterfile).map! { |item| item.first }
     end
 
-    def intersect(other)
-      # TODO
-    end
-
     private
     def rosterfile
       @fs.roster @course.name, @semester

lib/kgrader/task.rb

@@ -10,9 +10,13 @@ module KGrader
     end
 
     def grade(options = {})
+      students = @roster.students
+      students &= options[:students] unless options[:students].nil?
+
       # TODO
       puts "Grading #{@course.name}:#{@semester} assignment #{@assignment}..."
       puts "- options: #{options}"
+      puts "- students: #{students.inspect}"
     end
 
     def commit(options = {})