* Fix metadata copying
* Introduce a new metadata field `agg_tiles_hash_after_apply` for diff
files
* Added a lot of new info and debug logging
* Simplified Copying interface - not much value in having all the
complex builder pattern here it seems, might as well use a simple
object.
## Testing
* Generate SQLite DBs in memory on the fly to validate just what we need
* Use `insta` for validating DB content
There is now a function `dump(connection) -> Vec<Entry>` to dump the
content of the entire SQLite DB into text with `serde`. At many steps
through the testing, the DB content is validated with the corresponding
.snap file with `insta` crate (which makes this process mega-simple,
including a simple way to "bless" (update) any changes).
## Discovered bugs
* Seems like normalized files do not get copied properly - they contain
extras that should be removed.
