revlog: split functionality related to deltas computation in a new module...
revlog: split functionality related to deltas computation in a new module
The revlog module is getting big and this logic is getting more and more
advanced. Moving it to `mercurial.revlogutils.deltas` split a lot off
revlog.py and will help this logic to become less interleaved with revlog.
The code is simply moved without modification (but for namespace changes).
Refactoring and improvement will be made in later changesets.