From c05c8f31c1da29121def2159f7238d41a8e18f54 Mon Sep 17 00:00:00 2001
From: Robert Gleeson <rob@flowof.info>
Date: Sat, 21 Sep 2013 21:16:28 +0200
Subject: [PATCH 1/2] add Pry::CommandSet#[]=.

Pry::CommandSet#[]= can be used to re-assign commands or add new ones to
a command set. The key matches the pattern of a command you'd like to
replace and the value is the command you'd the pattern to be matched
with.

The key is really important. You could say this:

Pry.commands.command "hello" do
  output.puts "Hello! :)"
end
Pry.commands["help"] = Pry.commands["hello"]

I would expect "help" to print "Hello! :)", but the command is bound to
the pattern "hello". A new copy of the "hello" command is created
and the key is used as the match pattern, so "help" will print "Hello! :)".

You can use #[]= to replace commands, maybe your own 'help' implementation:
Pry.commands["help"] = MyHelpCommand

Commands can also be deleted by assigning a value of nil:
Pry.commands["help"] = nil

I decided to implement this based on SO post found here:
http://stackoverflow.com/questions/17475829/configure-help-output-in-pry
---
 lib/pry/command_set.rb | 58 +++++++++++++++++++++++++++++++++++-------
 1 file changed, 49 insertions(+), 9 deletions(-)

diff --git a/lib/pry/command_set.rb b/lib/pry/command_set.rb
index ecefa8b1..19a3fa7f 100644
--- a/lib/pry/command_set.rb
+++ b/lib/pry/command_set.rb
@@ -152,12 +152,6 @@ class Pry
       @commands.each(&block)
     end
 
-    # Add a given command object to this set.
-    # @param [Command] command The subclass of Pry::Command you wish to add.
-    def add_command(command)
-      commands[command.match] = command
-    end
-
     # Removes some commands from the set
     # @param [Array<String>] searches the matches or listings of the commands to remove
     def delete(*searches)
@@ -317,10 +311,56 @@ class Pry
     # Find a command that matches the given line
     # @param [String] val The line that might be a command invocation
     # @return [Pry::Command, nil]
-    def find_command(val)
-      commands.values.select{ |c| c.matches?(val) }.sort_by{ |c| c.match_score(val) }.last
+    def [](pattern)
+      commands.values.select do |command|
+        command.matches?(pattern)
+      end.sort_by do |command|
+        command.match_score(pattern)
+      end.last
+    end
+    alias_method :find_command, :[]
+
+    #
+    # Re-assign the command found at _pattern_ with _command_.
+    #
+    # @param [Regexp, String] pattern
+    #   The command to add or replace(found at _pattern_).
+    #
+    # @param [Pry::Command] command
+    #   The command to add.
+    #
+    # @return [Pry::Command]
+    #   Returns the new command (matched with "pattern".)
+    #
+    # @example
+    #   Pry.commands["help"] = MyHelpCommand
+    #
+    def []=(pattern, command)
+      if command.equal?(nil)
+        return commands.delete(pattern)
+      end
+      unless command < Pry::Command
+        raise TypeError, "command is not a subclass of Pry::Command"
+      end
+      bind_command_to_pattern = pattern != command.match
+      if bind_command_to_pattern
+        command_copy = command.dup
+        command_copy.match = pattern
+        @commands[pattern] = command_copy
+      else
+        @commands[pattern] = command
+      end
+    end
+
+    #
+    # Add a command to set.
+    #
+    # @param [Command] command
+    #   a subclass of Pry::Command.
+    #
+    def add_command(command)
+      self[command.match] = command
     end
-    alias_method :[], :find_command
 
     # Find the command that the user might be trying to refer to.
     # @param [String] search The user's search.

From df4b2aa14e0c0e7ee9d04a5d13c0f034f3982d51 Mon Sep 17 00:00:00 2001
From: Robert Gleeson <rob@flowof.info>
Date: Sun, 22 Sep 2013 11:21:51 +0200
Subject: [PATCH 2/2] add basic CommandSet#[]= tests.

---
 spec/command_set_spec.rb | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/spec/command_set_spec.rb b/spec/command_set_spec.rb
index 15fd7be8..3dcc2f47 100644
--- a/spec/command_set_spec.rb
+++ b/spec/command_set_spec.rb
@@ -12,6 +12,26 @@ describe Pry::CommandSet do
     }
   end
 
+  describe "[]=" do
+    it "removes a command from the command set" do
+      @set["help"].should.not == nil
+      @set["help"] = nil
+      @set["help"].should == nil
+      lambda { @set.run_command(TOPLEVEL_BINDING, "help") }.should.raise Pry::NoCommandError
+    end
+
+    it "replaces a command" do
+      old_help = @set["help"]
+      @set["help"] = @set["pry-version"]
+      @set["help"].should.not == old_help
+    end
+
+    it "rebinds the command with key" do
+      @set["help-1"] = @set["help"]
+      @set["help-1"].match.should == "help-1"
+    end
+  end
+
   it 'should call the block used for the command when it is called' do
     run = false
     @set.command 'foo' do