copy/paste: Make the clipboard contents persist after the process

ends.

For example, this lets you copy some files, exit nemo, restart
nemo, then paste.

Older versions persisted for 30s after closing, which allowed this
sort of behavior as a side effect.

Fixes #2800.

Author: mtwebster

src/nemo-tree-sidebar.c

@@ -958,6 +958,7 @@ static void
 copy_or_cut_files (FMTreeView *view,
 		   gboolean cut)
 {
+    GtkClipboard *clipboard;
 	char *status_string, *name;
 	NemoClipboardInfo info;
         GtkTargetList *target_list;
@@ -975,11 +976,14 @@ copy_or_cut_files (FMTreeView *view,
         targets = gtk_target_table_new_from_list (target_list, &n_targets);
         gtk_target_list_unref (target_list);
 
-	gtk_clipboard_set_with_data (nemo_clipboard_get (GTK_WIDGET (view->details->tree_widget)),
-				     targets, n_targets,
-				     nemo_get_clipboard_callback, nemo_clear_clipboard_callback,
-				     NULL);
-        gtk_target_table_free (targets, n_targets);
+    clipboard = nemo_clipboard_get (GTK_WIDGET (view));
+
+    gtk_clipboard_set_with_data (clipboard,
+                                 targets, n_targets,
+                                 nemo_get_clipboard_callback, nemo_clear_clipboard_callback,
+                                 NULL);
+    gtk_clipboard_set_can_store (clipboard, NULL, 0);
+    gtk_target_table_free (targets, n_targets);
 
 	nemo_clipboard_monitor_set_clipboard_info (nemo_clipboard_monitor_get (),
 	                                               &info);

src/nemo-view.c

@@ -6742,6 +6742,7 @@ copy_or_cut_files (NemoView *view,
 		   GList           *clipboard_contents,
 		   gboolean         cut)
 {
+    GtkClipboard *clipboard;
 	int count;
 	char *status_string, *name;
 	NemoClipboardInfo info;
@@ -6760,11 +6761,14 @@ copy_or_cut_files (NemoView *view,
         targets = gtk_target_table_new_from_list (target_list, &n_targets);
         gtk_target_list_unref (target_list);
 
-	gtk_clipboard_set_with_data (nemo_clipboard_get (GTK_WIDGET (view)),
-				     targets, n_targets,
-				     nemo_get_clipboard_callback, nemo_clear_clipboard_callback,
-				     NULL);
-        gtk_target_table_free (targets, n_targets);
+    clipboard = nemo_clipboard_get (GTK_WIDGET (view));
+
+    gtk_clipboard_set_with_data (clipboard,
+                                 targets, n_targets,
+                                 nemo_get_clipboard_callback, nemo_clear_clipboard_callback,
+                                 NULL);
+    gtk_clipboard_set_can_store (clipboard, NULL, 0);
+    gtk_target_table_free (targets, n_targets);
 
 	nemo_clipboard_monitor_set_clipboard_info (nemo_clipboard_monitor_get (), &info);