[devhelp] Book: improve doc of cmp_by_id()

[Sébastien Wilmet <swilmet src gnome org>]

commit 30e7e7cbd24318c7a2b4007a1176cd9173db8f80
Author: Sébastien Wilmet <swilmet gnome org>
Date:   Sun Dec 10 11:53:03 2017 +0100

    Book: improve doc of cmp_by_id()

 src/dh-book.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/src/dh-book.c b/src/dh-book.c
index fbe8b23..c0b6a25 100644
--- a/src/dh-book.c
+++ b/src/dh-book.c
@@ -603,7 +603,7 @@ dh_book_cmp_by_path (DhBook *a,
  * @a: a #DhBook.
  * @b: a #DhBook.
  *
- * Compares the #DhBook's by their IDs.
+ * Compares the #DhBook's by their IDs, with g_ascii_strcasecmp().
  *
  * Returns: an integer less than, equal to, or greater than zero, if @a is <, ==
  * or > than @b.