make mq and tags hardlink safe
The code didn't check for modes like "r+" or "rb+".
Many thanks to agriffis for noticing it.
% init
adding foo to series file
applying foo
Now at: foo
adding bar to series file
applying bar
Now at: bar
9373c9d7b61ff62edc4685b85115a54aa92cd6fa:foo
6dd08b80614ae7ed7f9224fb089e90deb999ae76:bar
%
foo
bar
%%%
9373c9d7b61ff62edc4685b85115a54aa92cd6fa:foo
%
foo
%%%
6dd08b80614ae7ed7f9224fb089e90deb999ae76 foo
9373c9d7b61ff62edc4685b85115a54aa92cd6fa bar
%
6dd08b80614ae7ed7f9224fb089e90deb999ae76 lfoo
9373c9d7b61ff62edc4685b85115a54aa92cd6fa lbar
%%%
6dd08b80614ae7ed7f9224fb089e90deb999ae76 foo
%
6dd08b80614ae7ed7f9224fb089e90deb999ae76 lfoo