cat: default to working dir parent instead of tip
This introduces a defaultrev function that chooses
the working dir parent if a revision isn't specified,
and uses it in several places.
#!/bin/sh
hg init rep
cd rep
mkdir dir
touch foo dir/bar
hg -v addremove
hg -v commit -m "add 1" -d "1000000 0"
cd dir/
touch ../foo_2 bar_2
hg -v addremove
hg -v commit -m "add 2" -d "1000000 0"
cd ..
hg init sim
cd sim
echo a > a
echo a >> a
echo a >> a
echo c > c
hg commit -Ama
mv a b
rm c
echo d > d
hg addremove -s 0.5
hg commit -mb