hgweb: use patch.diff() to make sensible diffs (
issue1223,
issue1258)
This gets us git diffs when enabled and doesn't pick erratic file parents.
#!/bin/sh
hg init dir
cd dir
echo bleh > bar
hg add bar
hg ci -m 'add bar'
hg cp bar foo
echo >> bar
hg ci -m 'cp bar foo; change bar'
hg debugrename foo
hg debugindex .hg/store/data/bar.i