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
hg init repo
cd repo
touch foo
hg add foo
for i in 0 1 2 3 4 5 6 7 8 9 10 11; do
echo "foo-$i" >> foo
hg ci -m "foo-$i" -d "0 0"
done
for out in "%nof%N" "%%%H" "%b-%R" "%h" "%r"; do
echo "# foo-$out.patch"
hg export -v -o "foo-$out.patch" 2:tip
done