debug-delta-find: add a --source option
This will help us to understand the delta-find operation in different
situations.
https://bz.mercurial-scm.org/1089 $ hg init $ mkdir a $ echo a > a/b $ hg ci -Am m adding a/b $ hg rm a removing a/b $ hg ci -m m a $ mkdir a b $ echo a > a/b $ hg ci -Am m adding a/b $ hg rm a removing a/b $ cd bRelative delete: $ hg ci -m m ../a $ cd ..