CommitDiffRequest: Introduce `WhitespaceChanges`
requested to merge 4546-introduce-new-whitespacechanges-enum-and-deprecate-ignore_whitespace_change into master
In the CommitDiffRequest message, introduce a new enum
WhitespaceChanges and a corresponding field whitespace_changes. This
field will allow us to decide between --ignore-all-space,
--ignore-space-change or no none.
This field also overshadows the earlier field ignore_whitespace_change
which was a boolean value and could not be extended. The field
ignore_whitespace_change is now marked as deprecated.
Closes #4546 (closed)