Merge pull request #4560 from CocoaPods/yavuz/imp/UIWithPager

[User Interface] add method to pipe outputs to a pager

lib/cocoapods/user_interface.rb

@@ -368,6 +368,21 @@ module Pod
         warnings << { :message => message, :actions => actions, :verbose_only => verbose_only }
       end
 
+      # Pipes all output inside given block to a pager.
+      #
+      # @yield Code block in which inputs to {#puts} and {#print} methods will be printed to the piper.
+      #
+      def with_pager
+        prev_handler = Signal.trap('INT', 'IGNORE')
+        IO.popen((ENV['PAGER'] || 'less -R'), 'w') do |io|
+          UI.output_io = io
+          yield
+        end
+      ensure
+        Signal.trap('INT', prev_handler)
+        UI.output_io = nil
+      end
+
       private
 
       # @!group Helpers

spec/unit/user_interface_spec.rb

@@ -26,6 +26,18 @@ module Pod
       # TODO
     end
 
+    describe '#with_pager' do
+      it 'sets output_io' do
+        fd = IO.sysopen('/dev/null', 'w')
+        io = IO.new(fd)
+        IO.stubs(:popen).yields(io)
+        UI.with_pager do
+          UI.output_io.should == io
+        end
+        UI.output_io.should.be.nil
+      end
+    end
+
     describe '#labeled' do
       it 'prints nothing if value is nil' do
         UI.labeled('label', nil)