convert: mercurial_source: also search for copies in modified files
There are some corner cases where we may have a copy in a file that
isn't in the added list:
- the result of a hg copy --after --force
- after a merge across a (local) rename
merging baz and foo
1 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
merging foo and baz
1 files updated, 1 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
initializing destination new repository
scanning source...
sorting...
converting...
4 add foo bar
3 change foo
2 make bar and baz copies of foo
1 merge local copy
0 merge remote copy
comparing with ../orig
searching for changes
no changes found