Add support for play 69 syntax

`play 69` is a shortcut for `play --file #{_file_} --lines 69`. It plays
lines from the current file. Example (I omitted some useless
information):

  pry(main)> show-source hello
    def hello
      binding.pry
      true
      puts "hi"
      69
    end
  pry(main)> hello
    1: def hello
 => 2:   binding.pry
    3:   true
    4:   puts "hi"
    5:   69
    6: end
  pry(main)> play 5
  => 69
  pry(main)> play 3..4
  hi
  => nil
  pry(main)>

Signed-off-by: Kyrylo Silin <kyrylosilin@gmail.com>

lib/pry/commands/play.rb

@@ -22,7 +22,14 @@ class Pry
     attr_accessor :content
 
     def setup
-      self.content   = ""
+      self.content = ""
+      @integer_or_range = %r/
+        \A           # Example:
+          \d+        # 22
+          (?:\.{2,3} # ...
+          \d+)?      # 24
+        \z
+      /x             # Matches: "22..24" or "22".
     end
 
     def options(opt)
@@ -69,7 +76,11 @@ class Pry
     end
 
     def perform_play
-      process_non_opt
+      if args.first =~ @integer_or_range
+        process_first_argument
+      else
+        process_non_opt
+      end
 
       if opts.present?(:lines)
         self.content = restrict_to_lines(self.content, opts[:l])
@@ -81,5 +92,22 @@ class Pry
 
       eval_string << self.content
     end
+
+    # Tries to play lines from a file.
+    # Mimicking `play --file #{_file_} --lines 69`.
+    def process_first_argument
+      return unless _pry_.last_file
+
+      start_line, exclusive, end_line = args.first.split(/(\.{2,3})/)
+      lines = if exclusive.nil?
+                start_line.to_i
+              else
+                Range.new(start_line.to_i, end_line.to_i, exclusive.length == 3)
+              end
+
+      self.content << File.read(_pry_.last_file)
+      self.content = restrict_to_lines(self.content, lines)
+    end
+
   end
 end

spec/commands/play_spec.rb

@@ -5,22 +5,66 @@ describe "play" do
     @t = pry_tester
   end
 
-  it 'should play a string variable  (with no args)' do
-    eval_str = ''
+  describe "with an argument" do
+    before do
+      @eval_str = ''
+    end
 
-    @t.eval 'x = "\"hello\""'
-    @t.process_command 'play x', eval_str
+    describe "string variable" do
+      it "without --lines switch" do
+        @t.eval 'x = "\"hello\""'
+        @t.process_command 'play x', @eval_str
+        @eval_str.should == '"hello"'
+      end
 
-    eval_str.should == '"hello"'
-  end
+      it 'using --lines switch to select what to play' do
+        @t.eval 'x = "\"hello\"\n\"goodbye\"\n\"love\""'
+        @t.process_command 'play x --lines 1', @eval_str
+        @eval_str.should == "\"hello\"\n"
+      end
+    end
 
-  it 'should play a string variable  (with no args) using --lines to select what to play' do
-    eval_str = ''
+    describe "numbers" do
+      before do
+        @tempfile = Tempfile.new(%w|pry .rb|)
+        @tempfile.puts <<-EOS
+          bing = :bing
+          bang = :bang
+          bong = :bong
+        EOS
+        @tempfile.flush
 
-    @t.eval 'x = "\"hello\"\n\"goodbye\"\n\"love\""'
-    @t.process_command 'play x --lines 1', eval_str
+        @t.eval %|_pry_.last_file = "#{ @tempfile.path }"|
+      end
 
-    eval_str.should == "\"hello\"\n"
+      after do
+        @tempfile.close(true)
+      end
+
+      describe "integer" do
+        it "should process one line from _pry_.last_file" do
+          @t.process_command 'play 1', @eval_str
+          @eval_str.should =~ /bing = :bing\n/
+        end
+      end
+
+      describe "range" do
+        it "should process multiple lines at once from _pry_.last_file" do
+          @t.process_command 'play 1..3', @eval_str
+          [/bing = :bing\n/, /bang = :bang\n/, /bong = :bong\n/].each { |str|
+            @eval_str.should =~ str
+          }
+        end
+      end
+    end
+
+    describe "malformed" do
+      it "should return nothing" do
+        @t.process_command 'play 69', @eval_str
+        @eval_str.should == ''
+        lambda { @t.process_command('play zZz') }.should.raise Pry::CommandError
+      end
+    end
   end
 
   it 'should play documentation with the -d switch' do