[devhelp] (3 commits) Non-fast-forward update to branch wip/swilmet/various-code-improvements

[Sébastien Wilmet <swilmet src gnome org>]

The branch 'wip/swilmet/various-code-improvements' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  579fb5f... book-tree: be able to jump back to the currently selected i
  a4f4215... book-tree: fix get_selected_book() when books are grouped b

Commits added to the branch:

  bd3cd7f... book-tree: be able to jump back to the currently selected i
  1de6b9e... book-tree: fix get_selected_book() when books are grouped b
  c2a1db2... book-tree: add some internal checks