[ruby/irb] Fix % escape in prompt format

(https://github.com/ruby/irb/pull/927)

https://github.com/ruby/irb/commit/08eee25d28

1 files changed, 2 insertions, 2 deletions

diff --git a/lib/irb.rb b/lib/irb.rb
index f7019ab0ea..d6afd6e510 100644
--- a/lib/irb.rb
+++ b/lib/irb.rb
@@ -1457,7 +1457,7 @@ module IRB
     end
 
     def format_prompt(format, ltype, indent, line_no) # :nodoc:
-      format.gsub(/%([0-9]+)?([a-zA-Z])/) do
+      format.gsub(/%([0-9]+)?([a-zA-Z%])/) do
         case $2
         when "N"
           @context.irb_name
@@ -1490,7 +1490,7 @@ module IRB
             line_no.to_s
           end
         when "%"
-          "%"
+          "%" unless $1
         end
       end
     end