[ruby/irb] Implement `history` command

(https://github.com/ruby/irb/pull/761)

* Implement `history` command

Lists IRB input history with indices. Also aliased as `hist`.

* Add tests for `history` command

* Address feedback: `puts` with multiple arguments instead of `join`ing

* Address feedback: Handle nil from splitting an empty input string

* Refactor line truncation

* Add `-g` grep option to `history` command

* Add `history` command to README

* Remove unused `*args` parameter

* Allow spaces to be included in grep

* Allow `/` to be included in grep regex

* Handle `input` being an empty string

* Exclude "#{index}: " from matching the grep regex

* Add new line after joining

https://github.com/ruby/irb/commit/3f9eacbfa9

1 files changed, 64 insertions, 0 deletions

diff --git a/test/irb/test_cmd.rb b/test/irb/test_cmd.rb
index 345f04bcf2..a0a62e96d2 100644
--- a/test/irb/test_cmd.rb
+++ b/test/irb/test_cmd.rb
@@ -888,4 +888,68 @@ module TestIRB
       assert_match("command: ': code2'", out)
     end
   end
+
+  class HistoryCmdTest < CommandTestCase
+    def teardown
+      TestInputMethod.send(:remove_const, "HISTORY") if defined?(TestInputMethod::HISTORY)
+      super
+    end
+
+    def test_history
+      TestInputMethod.const_set("HISTORY", %w[foo bar baz])
+
+      out, err = without_rdoc do
+        execute_lines("history")
+      end
+
+      assert_include(out, <<~EOF)
+        2: baz
+        1: bar
+        0: foo
+      EOF
+      assert_empty err
+    end
+
+    def test_multiline_history_with_truncation
+      TestInputMethod.const_set("HISTORY", ["foo", "bar", <<~INPUT])
+        [].each do |x|
+          puts x
+        end
+      INPUT
+
+      out, err = without_rdoc do
+        execute_lines("hist")
+      end
+
+      assert_include(out, <<~EOF)
+        2: [].each do |x|
+             puts x
+           ...
+        1: bar
+        0: foo
+      EOF
+      assert_empty err
+    end
+
+    def test_history_grep
+      TestInputMethod.const_set("HISTORY", ["foo", "bar", <<~INPUT])
+        [].each do |x|
+          puts x
+        end
+      INPUT
+
+      out, err = without_rdoc do
+        execute_lines("hist -g each\n")
+      end
+
+      assert_include(out, <<~EOF)
+        2: [].each do |x|
+             puts x
+           ...
+      EOF
+      assert_empty err
+    end
+
+  end
+
 end