Add remove-tags command

This command removes the given tags (or all if none are specified) from
a bookmark's tag list.

doc/clark.texi

@@ -158,6 +158,11 @@ Replace @var{url}'s tags with @var{tags}. @var{tags} may be omitted,
 in which case all the tags for @var{url} are removed.
 @end deffn
 
+@deffn Command remove-tags URL [TAGS...]
+Remove @var{tags} from @var{url}'s tag list. If @var{tags} is omitted,
+remove all tags from @var{url}'s tag list.
+@end deffn
+
 @node Miscellaneous,  , Management, Usage
 @section Other things that can be done
 

lisp/Makefile

@@ -36,5 +36,5 @@ $(install-binaries): install-%: %
 $(uninstall-binaries): uninstall-%:
 	rm -f "$(DESTDIR)/bin/$*"
 
-clark: clark.lisp make-image.lisp
+clark: clark.lisp queries.lisp make-image.lisp
 	$(LISP) --load make-image.lisp

lisp/clark.lisp

@@ -285,6 +285,14 @@ Get a random bookmark. If TAG is given limit the result to a bookmark
 having the tag TAG."
   (format t "~a~%" (random-item (url-list tag))))
 
+(defcommand remove-tags (url &rest tags)
+  "Remove given tags from bookmark's tag list."
+  "Usage: clark remove-tags <url> [<tags> ...]
+
+Remove the given TAGS from URL's tag list. If no tags are given,
+remove all tags from bookmark."
+  (delete-tags url tags))
+
 (defcommand version ()
     "Show version."
     "Usage: clark version

lisp/queries.lisp

@@ -68,10 +68,22 @@
   (execute-non-query
    *db* (sql delete from "bookmark" where "url" = ?) url))
 
-(defun delete-tags (id)
+(defun delete-tags (id &optional tags)
   "Clear the tags for bookmark with id ID."
-  (execute-non-query *db* (sql delete from "bookmark_tag"
-                               where "bookmark_id" = ?) id))
+  (if tags
+      (map nil
+           (lambda (tag)
+             (execute-non-query
+              *db* (sql delete from "bookmark_tag"
+                        where "bookmark_id" = (select "rowid"
+                                                      from "bookmark"
+                                                      where "url" = ?)
+                        and "tag_id" in (select "rowid"
+                                                from "tag"
+                                                where "name" = ?))
+              id tag)) tags)
+      (execute-non-query *db* (sql delete from "bookmark_tag"
+                                   where "bookmark_id" = ?) id)))
 
 (defun get-bookmark-id (url)
   "Get the id of the bookmark for URL."