merge: fix spurious merges for copies in linear updates We make better use of contexts to accurately identify copies that don't need merges. Add a simple test and update other tests.

#!/bin/sh

echo 'syntax error' > badext.py
abspath=`pwd`/badext.py

echo '[extensions]' >> $HGRCPATH
echo "badext = $abspath" >> $HGRCPATH

hg -q help help