ob-sqlite: Add ability to open a database in readonly mode

* lisp/ob-sqlite.el (org-babel-header-args:sqlite):
(org-babel-execute:sqlite): Add new header argument :readonly.
* etc/ORG-NEWS (ob-sqlite: Added ability to open a database in
readonly mode): Announce the new header argument.

etc/ORG-NEWS

@@ -76,6 +76,24 @@ bibliography format requires them to be written in title-case.
 
 # This also includes changes in function behavior from Elisp perspective.
 
+*** ob-sqlite: Added ability to open a database in readonly mode
+
+Added option :readonly to ob-sqlite.
+
+When :readonly=true the database is opened in readonly mode. For example:
+
+#+begin_src sqlite :db /tmp/rip.db  :readonly yes  :exports both
+create table rip(a,b);
+#+end_src
+
+This results in an error such as:
+
+#+begin_example
+Runtime error near line 2: attempt to write a readonly database (8)
+[ Babel evaluation exited with code 1 ]
+#+end_example
+
+
 ** Miscellaneous
 *** Trailing =-= is now allowed in plain links
 

lisp/ob-sqlite.el

@@ -52,7 +52,8 @@
     (line      . :any)
     (list      . :any)
     (separator . :any)
-    (nullvalue . :any))
+    (nullvalue . :any)
+    (readonly-p . ((yes no))))
   "Sqlite specific header args.")
 
 (defun org-babel-expand-body:sqlite (body params)
@@ -76,7 +77,8 @@ This function is called by `org-babel-execute-src-block'."
 	(db (cdr (assq :db params)))
 	(separator (cdr (assq :separator params)))
 	(nullvalue (cdr (assq :nullvalue params)))
-	(headers-p (equal "yes" (cdr (assq :colnames params))))
+        (headers-p (equal "yes" (cdr (assq :colnames params))))
+        (readonly-p (equal "yes" (cdr (assq :readonly params))))
 	(others (delq nil (mapcar
 			   (lambda (arg) (car (assq arg params)))
 			   (list :header :echo :bail :column
@@ -85,7 +87,7 @@ This function is called by `org-babel-execute-src-block'."
       (insert
        (org-babel-eval
 	(org-fill-template
-	 "%cmd %header %separator %nullvalue %others %csv %db "
+	 "%cmd %header %separator %nullvalue %others %csv %readonly %db "
 	 (list
 	  (cons "cmd" org-babel-sqlite3-command)
 	  (cons "header" (if headers-p "-header" "-noheader"))
@@ -103,6 +105,8 @@ This function is called by `org-babel-execute-src-block'."
 			      (member :html others) separator)
 			  ""
 			"-csv"))
+	  (cons "readonly"
+		(if readonly-p "-readonly" ""))
           (cons "db" (or db ""))))
 	;; body of the code block
 	(org-babel-expand-body:sqlite body params)))