babel: evaluation of code blocks now requires confirmation

* lisp/babel/ob.el (org-confirm-babel-evaluate): variable used to
  control evaluation of code blocks, default value it t, meaning all
  code block evaluation requires confirmation

  (org-babel-confirm-evaluate): function used to request confirmation
  of code block evaluation from the user

  (org-babel-execute-src-block): this function is the single point of
  entry for evaluation of code blocks (whether initiated through lob
  call, through direct code block evaluation, or as part of file
  exportation).  Every time this function is called it will now
  request confirmation from the user.  The newly added
  `org-confirm-babel-evaluate' variable can be used to configure this
  behavior.

  (org-babel-no-eval-on-ctrl-c-ctrl-c): This variable can be used to
  inhibit evaluation of code blocks with C-c C-c.

* lisp/org.el (org-ctrl-c-ctrl-c): added documentation of code block
  evaluation behavior

* lisp/babel/ob-keys.el (org-babel-key-bindings): adding keybindings
  for executing code blocks and for opening their results

lisp/babel/ob-keys.el

@@ -51,7 +51,11 @@ functions.")
   (describe-bindings org-babel-key-prefix))
 
 (defvar org-babel-key-bindings
-  '(("\C-p" . org-babel-expand-src-block)
+  '(("e" . org-babel-execute-src-block)
+    ("\C-e" . org-babel-execute-src-block)
+    ("o" . org-babel-open-src-block-result)
+    ("\C-o" . org-babel-open-src-block-result)
+    ("\C-p" . org-babel-expand-src-block)
     ("p" . org-babel-expand-src-block)
     ("g" . org-babel-goto-named-source-block)
     ("\C-b" . org-babel-execute-buffer)

lisp/babel/ob.el

@@ -61,6 +61,34 @@
 (declare-function org-babel-ref-variables "ob-ref" (params))
 (declare-function org-babel-ref-resolve-reference "ob-ref" (ref &optional params))
 
+(defcustom org-confirm-babel-evaluate t
+  "Require confirmation before interactively evaluating code
+blocks in Org-mode buffers.  The default value of this variable
+is t, meaning confirmation is required for any code block
+evaluation.  This variable can be set to nil to inhibit any
+future confirmation requests.  This variable can also be set to a
+function which takes two arguments the language of the code block
+and the body of the code block.  Such a function should then
+return a non-nil value if the user should be prompted for
+execution or nil if no prompt is required.
+
+Warning: Disabling confirmation may result in accidental
+evaluation of potentially harmful code.  It may be advisable
+remove code block execution from C-c C-c as further protection
+against accidental code block evaluation.  The
+`org-babel-no-eval-on-ctrl-c-ctrl-c' variable can be used to
+remove code block execution from the C-c C-c keybinding."
+  :group 'org-babel
+  :type '(choice boolean function))
+;; don't allow this variable to be changed through file settings
+(put 'org-confirm-babel-evaluate 'safe-local-variable (lambda (x) (eq x t)))
+
+(defcustom org-babel-no-eval-on-ctrl-c-ctrl-c nil
+  "This variable can be set to remove code block evaluation from
+the C-c C-c key binding."
+  :group 'org-babel
+  :type 'boolean)
+
 (defvar org-babel-source-name-regexp
   "^[ \t]*#\\+\\(srcname\\|source\\|function\\):[ \t]*"
   "Regular expression used to match a source name line.")
@@ -134,15 +162,34 @@ added to the header-arguments-alist."
           (org-babel-parse-inline-src-block-match)
         nil))))
 
+(defun org-babel-confirm-evaluate (info)
+  "Confirm that the user wishes to evaluate the code block
+defined by INFO.  This behavior can be suppressed by setting the
+value of `org-confirm-babel-evaluate' to nil, in which case all
+future interactive code block evaluations will proceed without
+any confirmation from the user.
+
+Note disabling confirmation may result in accidental evaluation
+of potentially harmful code."
+  (unless (or (not (if (functionp org-confirm-babel-evaluate)
+		       (funcall org-confirm-babel-evaluate
+				(nth 0 info) (nth 1 info))
+		     org-confirm-babel-evaluate))
+	      (yes-or-no-p
+	       (format "Evaluate this%scode on your system?"
+		       (if info (format " %s " (nth 0 info)) " "))))
+    (error "evaluation aborted")))
+
 ;;;###autoload
 (defun org-babel-execute-src-block-maybe ()
   "Detect if this is context for a org-babel src-block and if so
 then run `org-babel-execute-src-block'."
   (interactive)
-  (let ((info (org-babel-get-src-block-info)))
-    (if info
-        (progn (org-babel-execute-src-block current-prefix-arg info) t) nil)))
-
+  (if (not org-babel-no-eval-on-ctrl-c-ctrl-c)
+      (let ((info (org-babel-get-src-block-info)))
+	(if info
+	    (progn (org-babel-execute-src-block current-prefix-arg info) t) nil))
+    nil))
 (add-hook 'org-ctrl-c-ctrl-c-hook 'org-babel-execute-src-block-maybe)
 
 ;;;###autoload
@@ -241,6 +288,10 @@ the header arguments specified at the front of the source code
 block."
   (interactive)
   (let* ((info (or info (org-babel-get-src-block-info)))
+	 ;; note the `evaluation-confirmed' variable is currently not
+	 ;; used, but could be used later to avoid the need for
+	 ;; chaining confirmations
+	 (evaluation-confirmed (org-babel-confirm-evaluate info))
          (lang (nth 0 info))
 	 (params (setf (nth 2 info)
                        (sort (org-babel-merge-params (nth 2 info) params)

lisp/org.el

@@ -17021,7 +17021,13 @@ This command does many different things, depending on context:
 - If the cursor is on a numbered item in a plain list, renumber the
   ordered list.
 
-- If the cursor is on a checkbox, toggle it."
+- If the cursor is on a checkbox, toggle it.
+
+- If the cursor is on a code block, evaluate it.  The variable
+  `org-confirm-babel-evaluate' can be used to control prompting
+  before code block evaluation, by default every code block
+  evaluation requires confirmation.  Code block evaluation can be
+  inhibited by setting `org-babel-no-eval-on-ctrl-c-ctrl-c'."
   (interactive "P")
   (let  ((org-enable-table-editor t))
     (cond