[gnome-software] fedora distro upgrades: Only allow N+1 and N+2 upgrades

[Kalev Lember <klember src gnome org>]

commit 79e0e64c8985860def644225c92d80200cd9aef9
Author: Kalev Lember <klember redhat com>
Date:   Thu Nov 10 15:54:49 2016 +0000

    fedora distro upgrades: Only allow N+1 and N+2 upgrades
    
    Any bigger jump is unsupported by Fedora and likely to not work right.

 src/plugins/gs-plugin-fedora-distro-upgrades.c |   19 +++++++++++++++++--
 1 files changed, 17 insertions(+), 2 deletions(-)
---
diff --git a/src/plugins/gs-plugin-fedora-distro-upgrades.c b/src/plugins/gs-plugin-fedora-distro-upgrades.c
index 7fe5280..82bb7bf 100644
--- a/src/plugins/gs-plugin-fedora-distro-upgrades.c
+++ b/src/plugins/gs-plugin-fedora-distro-upgrades.c
@@ -321,6 +321,19 @@ get_upgrade_css_background (guint version)
        return g_strdup_printf ("#151E65");
 }
 
+static gint
+sort_distros_cb (gconstpointer a, gconstpointer b)
+{
+       DistroInfo *distro_a = *((DistroInfo **) a);
+       DistroInfo *distro_b = *((DistroInfo **) b);
+
+       if (distro_a->version > distro_b->version)
+               return 1;
+       if (distro_a->version < distro_b->version)
+               return -1;
+       return 0;
+}
+
 gboolean
 gs_plugin_add_distro_upgrades (GsPlugin *plugin,
                               GsAppList *list,
@@ -352,6 +365,7 @@ gs_plugin_add_distro_upgrades (GsPlugin *plugin,
        distros = parse_pkgdb_collections_data (data, (gssize) len, error);
        if (distros == NULL)
                return FALSE;
+       g_ptr_array_sort (distros, sort_distros_cb);
        for (i = 0; i < distros->len; i++) {
                DistroInfo *distro_info = g_ptr_array_index (distros, i);
                g_autofree gchar *app_id = NULL;
@@ -367,8 +381,9 @@ gs_plugin_add_distro_upgrades (GsPlugin *plugin,
                if (g_strcmp0 (distro_info->name, priv->os_name) != 0)
                        continue;
 
-               /* only interested in newer versions */
-               if (distro_info->version <= priv->os_version)
+               /* only interested in newer versions, but not more than N+2 */
+               if (distro_info->version <= priv->os_version ||
+                   distro_info->version > priv->os_version + 2)
                        continue;
 
                /* only interested in non-devel distros */