'pu' has been renamed to 'seen' #1447
Description
Which version of the book is affected?
The v2 version of the book accessible via the website.
Describe the bug:
The Git maintainer has renamed the pubranch to seen. See: https://public-inbox.org/git/xmqqimfid2l1.fsf@gitster.c.googlers.com/
The pu branch is referenced in the book in a few places. So, they need to updated.