[evolution] EMFolderTreeModel: Let load folder structure on demand

[Milan Crha <mcrha src gnome org>]

commit 085f55ce3991a18c97371647a434b013b6ef7ea7
Author: Milan Crha <mcrha redhat com>
Date:   Fri Jan 10 11:52:55 2020 +0100

    EMFolderTreeModel: Let load folder structure on demand
    
    It worked for newly created folders, but not after start, when a recursive,
    aka complete, folder structure is requested from the CamelStore. After this
    change the user can expand a folder node to load its subfolders also for
    cases when the CamelStore sends a CamelFolderInfo with no child, but with
    a CAMEL_FOLDER_CHILDREN flag, which notifies the caller that children
    folders are available.
    
    Related to https://gitlab.gnome.org/GNOME/evolution-ews/issues/61

 src/mail/em-folder-tree-model.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/src/mail/em-folder-tree-model.c b/src/mail/em-folder-tree-model.c
index b4b37adb82..d43fb1e1c4 100644
--- a/src/mail/em-folder-tree-model.c
+++ b/src/mail/em-folder-tree-model.c
@@ -1443,6 +1443,8 @@ em_folder_tree_model_set_folder_info (EMFolderTreeModel *model,
        if (!fully_loaded)
                load = (fi->child == NULL) && !(fi->flags &
                        (CAMEL_FOLDER_NOCHILDREN | CAMEL_FOLDER_NOINFERIORS));
+       else
+               load = !fi->child && (fi->flags & CAMEL_FOLDER_CHILDREN) != 0;
 
        path = gtk_tree_model_get_path (GTK_TREE_MODEL (model), iter);
        path_row = gtk_tree_row_reference_new (GTK_TREE_MODEL (model), path);