bash_completion: support GNU sed 3 and non-GNU sed replaced command 'Q' introduced in GNU sed 4, in order to support platforms with older sed.

#!/bin/sh

hg init a
cd a
echo a > foo
hg add foo
hg commit -m 1 -d "0 0"
rm foo
hg remove foo
hg commit -m 2 -d "0 0"

cd ..
hg clone a b