Clarify the full_copy field semantics.

Author: TurboGit

src/common/history.h

@@ -64,7 +64,8 @@ typedef struct dt_history_copy_item_t
   GList *selops;
   GtkTreeView *items;
   dt_imgid_t copied_imageid;
-  gboolean full_copy;
+  gboolean full_copy; // bypass some IOP flags like IOP_FLAGS_UNSAFE_COPY
+                      // and IOP_FLAGS_HIDDEN, this is used for duplicate images.
   gboolean copy_iop_order;
   dt_history_copy_mode_t paste_mode;
 } dt_history_copy_item_t;