copies: refactor symmetricdifference as _findlimit
We only need to track the lowest revision seen, which makes things simpler.
#!/bin/sh
echo % test --time
hg --time help -q help 2>&1 | grep Time > /dev/null || echo --time failed
echo % test --profile
if "$TESTDIR/hghave" -q hotshot; then
# hotshot might be missing for licensing issues
hg --profile help -q help 2>&1 | grep ncalls > /dev/null || echo --profile failed
fi
echo % test --lsprof
if "$TESTDIR/hghave" -q lsprof; then
hg --lsprof help -q help 2>&1 | grep CallCount > /dev/null || echo --lsprof failed
fi