prevent deleting tags that have release nodes pointing to them

yes, the only way to "move" a tag in CVS is to delete it and add it again to the new set of file revisions you care about. so, preventing the delete operation effectively prevents moving tags, too.

i think this kind of idiot-proofness in the xcvs-* access control scripts is a top priority before the whole release system can go live (therefore, i'm assigning to myself and bumping to critical).

actually, there is a move operation for cvs tag (-F), so i'll just make sure we catch that case, too...

see also http://drupal.org/node/92653

to accomplish this feature, i changed xcvs_db_connect() to just store the active db connection in a static var, and xcvs_db_check_write_access() to not call mysql_close() (see http://us2.php.net/manual/en/function.mysql-close.php: "Using mysql_close() isn't usually necessary, as non-persistent open links are automatically closed at the end of the script's execution."). so, this way we can leave a single DB connection open, regardless of whatever queries we need to run...

while i was at it, i converted to mysql_real_escape_string() (since mysql_escape_string() is deprecated according to http://us2.php.net/manual/en/function.mysql-escape-string.php), and i added a few more paranoia checks in the SQL queries (casting variables to (int), that sort of thing)...

otherwise, this is a pretty simple feature/patch...

in IRC, natrak said this was RTBC, so i committed everything to the DRUPAL-4-7--2 branch. i didn't commit to HEAD since all the new release system hasn't been merged into there, yet, and this particular feature depends entirely on the releases-as-nodes stuff.