Catch illegal boolean values in hgrc nicely.
With hg 0.9.3 the section and parameter name wasn't printed,
with hg 0.9.4 there was a traceback for ValueError.
#!/bin/sh
hg init
touch a
hg add a
hg ci -m "a" -d "1000000 0"
echo 123 > b
hg add b
hg diff --nodates
hg diff --nodates -r tip
echo foo > a
hg diff --nodates
hg diff -r ""
hg diff -r tip -r ""
true