[ruby/irb] Display aliases in help message

(https://github.com/ruby/irb/pull/788)

Similar to Pry, it displays user-defined aliases in the help message with
a dedicated section. With the current default aliases, it looks like:

```
...other sections...

Aliases
  $              Alias for `show_source`
  @              Alias for `whereami`
```

https://github.com/ruby/irb/commit/2a0eacc891

1 files changed, 13 insertions, 1 deletions

diff --git a/lib/irb/context.rb b/lib/irb/context.rb
index a7b8ca2c26..3442fbf4da 100644
--- a/lib/irb/context.rb
+++ b/lib/irb/context.rb
@@ -146,9 +146,21 @@ module IRB
         @newline_before_multiline_output = true
       end
 
-      @command_aliases = IRB.conf[:COMMAND_ALIASES]
+      @user_aliases = IRB.conf[:COMMAND_ALIASES].dup
+      @command_aliases = @user_aliases.merge(KEYWORD_ALIASES)
     end
 
+    # because all input will eventually be evaluated as Ruby code,
+    # command names that conflict with Ruby keywords need special workaround
+    # we can remove them once we implemented a better command system for IRB
+    KEYWORD_ALIASES = {
+      :break => :irb_break,
+      :catch => :irb_catch,
+      :next => :irb_next,
+    }.freeze
+
+    private_constant :KEYWORD_ALIASES
+
     private def build_completor
       completor_type = IRB.conf[:COMPLETOR]
       case completor_type