Bugfix: properly restore workspace containers (Thanks vals)

fixes #1306

include/load_layout.h

@@ -2,7 +2,7 @@
  * vim:ts=4:sw=4:expandtab
  *
  * i3 - an improved dynamic tiling window manager
- * © 2009-2011 Michael Stapelberg and contributors (see also: LICENSE)
+ * © 2009-2014 Michael Stapelberg and contributors (see also: LICENSE)
  *
  * load_layout.c: Restore (parts of) the layout, for example after an inplace
  *                restart.
@@ -10,4 +10,25 @@
  */
 #pragma once
 
+typedef enum {
+    // We could not determine the content of the JSON file. This typically
+    // means it’s unreadable or contains garbage.
+    JSON_CONTENT_UNKNOWN = 0,
+
+    // The JSON file contains a “normal” container, i.e. a container to be
+    // appended to an existing workspace (or split container!).
+    JSON_CONTENT_CON = 1,
+
+    // The JSON file contains a workspace container, which needs to be appended
+    // to the output (next to the other workspaces) with special care to avoid
+    // naming conflicts and ensuring that the workspace _has_ a name.
+    JSON_CONTENT_WORKSPACE = 2,
+} json_content_t;
+
+/* Parses the given JSON file until it encounters the first “type” property to
+ * determine whether the file contains workspaces or regular containers, which
+ * is important to know when deciding where (and how) to append the contents.
+ * */
+json_content_t json_determine_content(const char *filename);
+
 void tree_append_json(Con *con, const char *filename, char **errormsg);