Get add and locate to use new repo and dirstate walk code. They use a walk function that abstracts out the irritating details, so that there's a higher likelihood of commands behaving uniformly.

#!/bin/sh

hg init
touch a
hg add a
hg ci -t "a" -u test -d "0 0"

echo 123 > b
hg add b
hg diff | sed "s/\(\(---\|+++\).*\)\t.*/\1/"

hg diff -r tip | sed "s/\(\(---\|+++\).*\)\t.*/\1/"