Add helper to create a file list from bundles

In order to support verify_fix_path from bundle_add, a generic file list
from bundle list needs to be implemented to replace the one embedded in
the current consolidate_submanifests function.

This function will be used to generate a file list to be passed to a new
function for consolidating a list of files (created in the following
patch).

Note the list of files this creates is not sorted.

include/swupd.h

@@ -257,6 +257,7 @@ void delete_motd(void);
 extern int get_dirfd_path(const char *fullname);
 extern int verify_fix_path(char *targetpath, struct manifest *manifest);
 extern void set_local_download(void);
+extern struct list *files_from_bundles(struct list *bundles);
 
 /* subscription.c */
 struct list *free_list_file(struct list *item);

src/helpers.c

@@ -851,3 +851,24 @@ void set_local_download(void)
 
 	return;
 }
+
+struct list *files_from_bundles(struct list *bundles)
+{
+	struct list *files = NULL;
+	struct list *list;
+	struct manifest *bundle;
+
+	list = list_head(bundles);
+	while (list) {
+		struct list *bfiles;
+		bundle = list->data;
+		list = list->next;
+		if (!bundle) {
+			continue;
+		}
+		bfiles = list_clone(bundle->files);
+		files = list_concat(bfiles, files);
+	}
+
+	return files;
+}