[gnome-software] Do not allow the management plugin to be changed

[Richard Hughes <rhughes src gnome org>]

commit 09c984f9000005b61c4f4b83b7ac64ce6aaf6789
Author: Richard Hughes <richard hughsie com>
Date:   Thu Aug 4 08:08:54 2016 +0100

    Do not allow the management plugin to be changed

 src/gs-app.c |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletions(-)
---
diff --git a/src/gs-app.c b/src/gs-app.c
index 253b62b..a850b63 100644
--- a/src/gs-app.c
+++ b/src/gs-app.c
@@ -1893,16 +1893,30 @@ gs_app_get_management_plugin (GsApp *app)
  *
  * The management plugin is the plugin that can handle doing install and remove
  * operations on the #GsApp.
- * Typical values include "packagekit" and "jhbuild"
+ * Typical values include "packagekit" and "flatpak"
+ *
+ * It is an error to attempt to change the management plugin once
+ * it has been previously set.
  **/
 void
 gs_app_set_management_plugin (GsApp *app, const gchar *management_plugin)
 {
        g_return_if_fail (GS_IS_APP (app));
 
+       /* same */
        if (g_strcmp0 (app->management_plugin, management_plugin) == 0)
                return;
 
+       /* trying to change */
+       if (app->management_plugin != NULL && management_plugin != NULL) {
+               g_warning ("automatically prevented from changing "
+                          "management plugin on %s from %s to %s!",
+                          gs_app_get_id (app),
+                          app->management_plugin,
+                          management_plugin);
+               return;
+       }
+
        g_free (app->management_plugin);
        app->management_plugin = g_strdup (management_plugin);
 }