Handle 'deletable' cell metadata

IPython/html/static/notebook/js/cell.js

@@ -385,7 +385,8 @@ define([
      **/
     Cell.prototype.toJSON = function () {
         var data = {};
-        data.metadata = this.metadata;
+        // deepcopy the metadata so copied cells don't share the same object
+        data.metadata = JSON.parse(JSON.stringify(this.metadata));
         data.cell_type = this.cell_type;
         return data;
     };
@@ -404,22 +405,32 @@ define([
 
 
     /**
-     * can the cell be split into two cells
+     * can the cell be split into two cells (false if not deletable)
      * @method is_splittable
      **/
     Cell.prototype.is_splittable = function () {
-        return true;
+        return this.is_deletable();
     };
 
 
     /**
-     * can the cell be merged with other cells
+     * can the cell be merged with other cells (false if not deletable)
      * @method is_mergeable
      **/
     Cell.prototype.is_mergeable = function () {
-        return true;
+        return this.is_deletable();
     };
 
+    /**
+     * is the cell deletable? (true by default)
+     * @method is_deletable
+     **/
+    Cell.prototype.is_deletable = function () {
+        if (this.metadata.deletable === undefined) {
+            return true;
+        }
+        return Boolean(this.metadata.deletable);
+    };
 
     /**
      * @return {String} - the text before the cursor

IPython/html/static/notebook/js/notebook.js

@@ -765,7 +765,11 @@ define([
      */
     Notebook.prototype.delete_cell = function (index) {
         var i = this.index_or_selected(index);
-        var cell = this.get_selected_cell();
+        var cell = this.get_cell(i);
+        if (!cell.is_deletable()) {
+            return this;
+        }
+
         this.undelete_backup = cell.toJSON();
         $('#undelete_cell').removeClass('disabled');
         if (this.is_valid_cell_index(i)) {
@@ -1193,6 +1197,10 @@ define([
     Notebook.prototype.copy_cell = function () {
         var cell = this.get_selected_cell();
         this.clipboard = cell.toJSON();
+        // remove undeletable status from the copied cell
+        if (this.clipboard.metadata.deletable !== undefined) {
+            delete this.clipboard.metadata.deletable;
+        }
         this.enable_paste();
     };