irb: save repl history

This enables history for `brew irb` sessions.
It saves that history to the repository directory.

.gitignore

@@ -194,6 +194,7 @@
 !/.dockerignore
 !/.editorconfig
 !/.gitignore
+!/.irb_config
 !/.yardopts
 !/.vale.ini
 !/.shellcheckrc

.irb_config

@@ -0,0 +1,8 @@
+# Note that we use a non-standard config file name to reduce
+# name clashes with other IRB config files like `.irbrc`.
+
+require 'irb/completion'
+
+IRB.conf[:SAVE_HISTORY] = 100
+IRB.conf[:HISTORY_FILE] = "#{__dir__}/.irb_history"
+IRB.conf[:IRB_NAME] = "brew"

Library/Homebrew/dev-cmd/irb.rb

@@ -67,6 +67,8 @@ module Homebrew
     if args.pry?
       Pry.start
     else
+      ENV["IRBRC"] = (HOMEBREW_REPOSITORY/".irb_config").to_s
+
       IRB.start
     end
   end