Wrong english strings in book migration from D6->D8

Major?

Anyway, changes look good.

This seems like a good fix to do, but is not a severe enough bug fix to warrant breaking strings. Let's pick this back up in 8.1.x.

@xjm asked me if this was a disruption for translators or not. This is usually straightforward to tell with grep so:

$ git grep "mlid in the"
core/lib/Drupal/Core/Menu/MenuTreeStorage.php:          'description' => 'The first mlid in the materialized path. If N = depth, then pN must equal the mlid. If depth > 1 then p(N-1) must equal the parent link mlid. All pX where X > depth must equal zero. The columns p1 .. p9 are also called the parents.',
core/lib/Drupal/Core/Menu/MenuTreeStorage.php:          'description' => 'The second mlid in the materialized path. See p1.',
core/lib/Drupal/Core/Menu/MenuTreeStorage.php:          'description' => 'The third mlid in the materialized path. See p1.',
core/lib/Drupal/Core/Menu/MenuTreeStorage.php:          'description' => 'The fourth mlid in the materialized path. See p1.',
core/lib/Drupal/Core/Menu/MenuTreeStorage.php:          'description' => 'The fifth mlid in the materialized path. See p1.',
core/lib/Drupal/Core/Menu/MenuTreeStorage.php:          'description' => 'The sixth mlid in the materialized path. See p1.',
core/lib/Drupal/Core/Menu/MenuTreeStorage.php:          'description' => 'The seventh mlid in the materialized path. See p1.',
core/lib/Drupal/Core/Menu/MenuTreeStorage.php:          'description' => 'The eighth mlid in the materialized path. See p1.',
core/lib/Drupal/Core/Menu/MenuTreeStorage.php:          'description' => 'The ninth mlid in the materialized path. See p1.',
core/modules/book/src/Plugin/migrate/source/d6/Book.php:      'p1' => $this->t('The first mlid in the materialized path.'),
core/modules/book/src/Plugin/migrate/source/d6/Book.php:      'p2' => $this->t('The second mlid in the materialized path.'),
core/modules/book/src/Plugin/migrate/source/d6/Book.php:      'p3' => $this->t('The third mlid in the materialized path.'),
core/modules/book/src/Plugin/migrate/source/d6/Book.php:      'p4' => $this->t('The fourth mlid in the materialized path.'),
core/modules/book/src/Plugin/migrate/source/d6/Book.php:      'p5' => $this->t('The fifth mlid in the materialized path.'),
core/modules/book/src/Plugin/migrate/source/d6/Book.php:      'p6' => $this->t('The sixth mlid in the materialized path.'),
core/modules/book/src/Plugin/migrate/source/d6/Book.php:      'p7' => $this->t('The seventh mlid in the materialized path.'),
core/modules/book/src/Plugin/migrate/source/d6/Book.php:      'p8' => $this->t('The eight mlid in the materialized path.'),
core/modules/book/src/Plugin/migrate/source/d6/Book.php:      'p9' => $this->t('The nine mlid in the materialized path.'),
core/modules/menu_link_content/src/Plugin/migrate/source/MenuLink.php:      'p1' => t('The first mlid in the materialized path. If N = depth, then pN must equal the mlid. If depth > 1 then p(N-1) must equal the plid. All pX where X > depth must equal zero. The columns p1 .. p9 are also called the parents.'),
core/modules/menu_link_content/src/Plugin/migrate/source/MenuLink.php:      'p2' => t('The second mlid in the materialized path. See p1.'),
core/modules/menu_link_content/src/Plugin/migrate/source/MenuLink.php:      'p3' => t('The third mlid in the materialized path. See p1.'),
core/modules/menu_link_content/src/Plugin/migrate/source/MenuLink.php:      'p4' => t('The fourth mlid in the materialized path. See p1.'),
core/modules/menu_link_content/src/Plugin/migrate/source/MenuLink.php:      'p5' => t('The fifth mlid in the materialized path. See p1.'),
core/modules/menu_link_content/src/Plugin/migrate/source/MenuLink.php:      'p6' => t('The sixth mlid in the materialized path. See p1.'),
core/modules/menu_link_content/src/Plugin/migrate/source/MenuLink.php:      'p7' => t('The seventh mlid in the materialized path. See p1.'),
core/modules/menu_link_content/src/Plugin/migrate/source/MenuLink.php:      'p8' => t('The eighth mlid in the materialized path. See p1.'),
core/modules/menu_link_content/src/Plugin/migrate/source/MenuLink.php:      'p9' => t('The ninth mlid in the materialized path. See p1.'),

The patch fixes strings in the book migration. These look unique to the book migration. However they are almost the same as the Menu migration and the actual menu tree storage strings. If only book migration would use the exact same strings, we would actually REMOVE a lot of noise for translators. Instead of just fixing the typo the patch should just use the exact same strings that are already used twice in core. That would result in no new strings for translators whatsoever (those who already translated core), and it would mean less strings to translate for those who did not. Win-win-win.

Also its reducing useless translator pain so would ideally be done in Drupal 8.0.x soon :)

For consistency I've changed all related strings. It also helps removing noise and translator pain, as @Gábor Hojtsy said.

Yay, less strings!

Less strings to translate - nice. And as these strings already exist going into 8.0.x makes sense. Committed 1eea7ae and pushed to 8.0.x and 8.1.x. Thanks!

Superb, thanks!