Use shutil.copystat in copyfile().
#!/bin/sh
echo "[extensions]" >> $HGRCPATH
echo "mq=" >> $HGRCPATH
hg init a
cd a
echo a > a
hg ci -Ama
hg qnew a.patch
echo a >> a
hg qrefresh
hg qnew b.patch
echo b > b
hg add b
hg qrefresh
hg qnew c.patch
echo c > c
hg add c
hg qrefresh
hg qgoto a.patch
hg qgoto c.patch
hg qgoto b.patch
echo
echo % Using index
hg qgoto 0
hg qgoto 2
echo
echo % No warnings when using index
hg qnew bug314159
echo d >> c
hg qrefresh
hg qnew bug141421
echo e >> c
hg qrefresh
hg qgoto 1
hg qgoto 3
echo
echo % Detect ambiguous non-index
hg qgoto 14
exit 0