merge-recursive: fix remainder of was_dirty() to use original index
was_dirty() uses was_tracked(), which has been updated to use the original index rather than the current one. However, was_dirty() also had a separate call to cache_file_exists(), causing it to still implicitly use the current index. Update that to instead use index_file_exists(). Also, was_dirty() had a hack where it would mark any file as non-dirty if we simply didn't know its modification time. This was due to using the current index rather than the original index, because D/F conflicts and such would cause unpack_trees() to not copy the modification times from the original index to the current one. Now that we are using the original index, we can dispense with this hack. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>