[gnome-software] trivial: Add some more verbage to the gs_app_get_to_be_installed() docs

[Richard Hughes <rhughes src gnome org>]

commit 80e19ae2b73b305196597951268840a71faa2400
Author: Richard Hughes <richard hughsie com>
Date:   Tue May 10 17:01:27 2016 +0100

    trivial: Add some more verbage to the gs_app_get_to_be_installed() docs

 src/gs-app.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/src/gs-app.c b/src/gs-app.c
index c6ba863..a8a97e5 100644
--- a/src/gs-app.c
+++ b/src/gs-app.c
@@ -2392,6 +2392,12 @@ gs_app_get_kudos_percentage (GsApp *app)
  *
  * Gets if the application is queued for installation.
  *
+ * This is only set for addons when the user has selected some addons to be
+ * installed before installing the main application.
+ * Plugins should check all the addons for this property when installing
+ * main applications so that the chosen set of addons is also installed at the
+ * same time. This is never set when applications do not have addons.
+ *
  * Returns: %TRUE for success
  **/
 gboolean