...
Implement a worker process pool for running many, short-lived jobs
...
...
Restore pre-refactor save to disk performance by running copy and metadata update in parallel
Review downloaded metadata: Add suggestions for the tags, authors, publishers and series fields. Suggestions will pop-up as you type. Fixes #1390887 [Tags suggestions in review downloaded metadata dialog](https://bugs.launchpad.net/calibre/+bug/1390887)
Remove unused code
Linux: Fix regression on Unity that prevented some keyboard shortcuts from working because of the global menu bar. Fixes #1390901 [Book Merge via Keyboard Shortcut Not Working](https://bugs.launchpad.net/calibre/+bug/1390901)
Add a facility to send common data (common to all jobs) to the workers in a pool
Send the plugboard cache only once per worker instead of once per job
Method that allows implementing has_book in a worker process with no access to the data
...
A spot of refactoring
Small optimization, only serialize common_data once instead of once per worker
...
Method to find identical books in worker processes without access to the db
Translate the title for the User Manual
Amazon metadata download: Fix cover not being found for some books because of a website change at amazon.com
More amazon cover finding fixes
Metadata download: Prioritize results that have the same language as the current calibre user interface language

Also allow plugins to override how merging treats results without an
ISBN