Enhance the file filtering capabilities.
We now allow filtering through either pipes or pairs of temporary
files. The latter appear to be mandatory for use on Windows.
#!/bin/sh
mkdir a
cd a
hg init
echo a > a
hg add a
hg commit -m test -d '0 0'
# Default operation
hg clone . ../b
cd ../b
cat a
hg verify
# No update
hg clone -U . ../c
cd ../c
cat a
hg verify
# Default destination
mkdir ../d
cd ../d
hg clone ../a
cd a
hg cat a