Respect users configured IRB.conf[:IRB_NAME]

If a user has configured `IRB_NAME` in their IRB configuration, Rails is overriding it. This PR makes it so the `IRB_NAME` is only set if it is not the default, similar to the way the `PROMPT_MODE` is set.

Author: jclusso

railties/lib/rails/commands/console/irb_console.rb

@@ -87,7 +87,8 @@ def start
 
         env = colorized_env
         prompt_prefix = "%N(#{env})"
-        IRB.conf[:IRB_NAME] = @app.name
+        # Respect user's configured irb name.
+        IRB.conf[:IRB_NAME] = @app.name if IRB.conf[:IRB_NAME] == "irb"
 
         IRB.conf[:PROMPT][:RAILS_PROMPT] = {
           PROMPT_I: "#{prompt_prefix}:%03n> ",

railties/test/application/console_test.rb

@@ -242,6 +242,21 @@ class User
     write_prompt "User.new.respond_to?(:age)", "=> true"
   end
 
+  def test_console_respects_user_defined_irb_name
+    irbrc = Tempfile.new("irbrc")
+    irbrc.write <<-RUBY
+      IRB.conf[:IRB_NAME] = "jarretts-irb"
+    RUBY
+    irbrc.close
+
+    options = "-e test"
+    spawn_console(options, env: { "IRBRC" => irbrc.path })
+
+    write_prompt "123", prompt: "jarretts-irb(test):002> "
+  ensure
+    File.unlink(irbrc)
+  end
+
   def test_console_respects_user_defined_prompt_mode
     irbrc = Tempfile.new("irbrc")
     irbrc.write <<-RUBY