[gcab] trivial: Return an error when adding a duplicate folder to a cabinet

[Richard Hughes <rhughes src gnome org>]

commit 89bb0054be0ad0a1743210cc4b479056429f227e
Author: Richard Hughes <richard hughsie com>
Date:   Tue Dec 12 20:45:45 2017 +0000

    trivial: Return an error when adding a duplicate folder to a cabinet

 libgcab/gcab-cabinet.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)
---
diff --git a/libgcab/gcab-cabinet.c b/libgcab/gcab-cabinet.c
index 771c3d1..10123d5 100644
--- a/libgcab/gcab-cabinet.c
+++ b/libgcab/gcab-cabinet.c
@@ -171,6 +171,15 @@ gcab_cabinet_add_folder (GCabCabinet *self,
     g_return_val_if_fail (GCAB_IS_FOLDER (folder), FALSE);
     g_return_val_if_fail (!error || *error == NULL, FALSE);
 
+    for (guint i = 0; i < self->folders->len; i++) {
+        GCabFolder *folder_tmp = g_ptr_array_index (self->folders, i);
+        if (folder_tmp == folder) {
+            g_set_error (error, GCAB_ERROR, GCAB_ERROR_FORMAT,
+                         "Folder has already been added");
+            return FALSE;
+        }
+    }
+
     g_ptr_array_add (self->folders, g_object_ref (folder));
 
     return TRUE;