pager.rb: fix Helpers constant invocation

Since the top class is Pry::Pager and not Pry, the cref constant static lookup
only look for constants under Pry::Pager (or at the top level).

Since Helpers refers to Pry::Helpers, it won't be found. Fix this by
changing the top class to Pry and put the class Pager in the Pry
namespace.

This introduce a two space shift of all the code, so reformat the
comments.

This also fixes the following bug: in SystemPager.available? the Helpers
constant lookup fails, so this raises an exception which is rescued and
then returns false; so the SimplePager is always chosen instead.

lib/pry/pager.rb

@@ -3,7 +3,8 @@ require 'pry/terminal'
 # A pager is an `IO`-like object that accepts text and either prints it
 # immediately, prints it one page at a time, or streams it to an external
 # program to print one page at a time.
-class Pry::Pager
+class Pry
+  class Pager
     class StopPaging < StandardError
     end
 
@@ -13,9 +14,10 @@ class Pry::Pager
       @_pry_ = _pry_
     end
 
-  # Send the given text through the best available pager (if `Pry.config.pager` is
+    # Send the given text through the best available pager (if
-  # enabled). If you want to send text through in chunks as you generate it, use `open`
+    # `Pry.config.pager` is enabled). If you want to send text through in
-  # to get a writable object instead.
+    # chunks as you generate it, use `open` to get a writable object
+    # instead.
     #
     # @param [String] text
     #   Text to run through a pager.
@@ -26,8 +28,8 @@ class Pry::Pager
       end
     end
 
-  # Yields a pager object (`NullPager`, `SimplePager`, or `SystemPager`).  All
+    # Yields a pager object (`NullPager`, `SimplePager`, or `SystemPager`).
-  # pagers accept output with `#puts`, `#print`, `#write`, and `#<<`.
+    # All pagers accept output with `#puts`, `#print`, `#write`, and `#<<`.
     def open
       pager = best_available
       yield pager
@@ -42,12 +44,13 @@ class Pry::Pager
 
     def output; @output; end
 
-  # Return an instance of the "best" available pager class -- `SystemPager` if
+    # Return an instance of the "best" available pager class --
-  # possible, `SimplePager` if `SystemPager` isn't available, and `NullPager`
+    # `SystemPager` if possible, `SimplePager` if `SystemPager` isn't
-  # if the user has disabled paging. All pagers accept output with `#puts`,
+    # available, and `NullPager` if the user has disabled paging. All
-  # `#print`, `#write`, and `#<<`. You must call `#close` when you're done
+    # pagers accept output with `#puts`, `#print`, `#write`, and `#<<`. You
-  # writing output to a pager, and you must rescue `Pry::Pager::StopPaging`.
+    # must call `#close` when you're done writing output to a pager, and
-  # These requirements can be avoided by using `.open` instead.
+    # you must rescue `Pry::Pager::StopPaging`. These requirements can be
+    # avoided by using `.open` instead.
     def best_available
       if !_pry_.config.pager
         NullPager.new(_pry_.output)
@@ -58,8 +61,8 @@ class Pry::Pager
       end
     end
 
-  # `NullPager` is a "pager" that actually just prints all output as it comes
+    # `NullPager` is a "pager" that actually just prints all output as it
-  # in. Used when `Pry.config.pager` is false.
+    # comes in. Used when `Pry.config.pager` is false.
     class NullPager
       def initialize(out)
         @out = out
@@ -92,8 +95,8 @@ class Pry::Pager
       end
     end
 
-  # `SimplePager` is a straightforward pure-Ruby pager. We use it on JRuby and
+    # `SimplePager` is a straightforward pure-Ruby pager. We use it on
-  # when we can't find a usable external pager.
+    # JRuby and when we can't find a usable external pager.
     class SimplePager < NullPager
       def initialize(*)
         super
@@ -118,14 +121,16 @@ class Pry::Pager
       end
     end
 
-  # `SystemPager` buffers output until we're pretty sure it's at least a page
+    # `SystemPager` buffers output until we're pretty sure it's at least a
-  # long, then invokes an external pager and starts streaming output to it. If
+    # page long, then invokes an external pager and starts streaming output
-  # `#close` is called before then, it just prints out the buffered content.
+    # to it. If `#close` is called before then, it just prints out the
+    # buffered content.
     class SystemPager < NullPager
       def self.default_pager
         pager = ENV["PAGER"] || ""
 
-      # Default to less, and make sure less is being passed the correct options
+        # Default to less, and make sure less is being passed the correct
+        # options
         if pager.strip.empty? or pager =~ /^less\b/
           pager = "less -R -F -X"
         end
@@ -198,14 +203,15 @@ class Pry::Pager
       end
     end
 
-  # `PageTracker` tracks output to determine whether it's likely to take up a
+    # `PageTracker` tracks output to determine whether it's likely to take
-  # whole page. This doesn't need to be super precise, but we can use it for
+    # up a whole page. This doesn't need to be super precise, but we can
-  # `SimplePager` and to avoid invoking the system pager unnecessarily.
+    # use it for `SimplePager` and to avoid invoking the system pager
+    # unnecessarily.
     #
-  # One simplifying assumption is that we don't need `#page?` to return `true`
+    # One simplifying assumption is that we don't need `#page?` to return
-  # on the basis of an incomplete line. Long lines should be counted as
+    # `true` on the basis of an incomplete line. Long lines should be
-  # multiple lines, but we don't have to transition from `false` to `true`
+    # counted as multiple lines, but we don't have to transition from
-  # until we see a newline.
+    # `false` to `true` until we see a newline.
     class PageTracker
       def initialize(rows, cols)
         @rows, @cols = rows, cols
@@ -240,4 +246,5 @@ class Pry::Pager
         line.chomp.gsub(/\e\[[\d;]*m/, '').length
       end
     end
+  end
 end