Add unrecord to Pijul demo

Dependencies

• [2] SQWPGFUE Finish the demos
• [*] ARAFRHKU Create the outline of the talk

Change contents

• edit in sections/6-pijul.md at line 118
  [2.2570]

  [2.2570]
  + pijul record

  +

  + pijul unrecord // unrecord all patches and squash them into one

  + pijul add .