When language pack maintainers review submitted contributions, they may want to make small corrections. But then the timeline history of individual strings does not contain correct information about who is the actual author of the translation. Was it part of the contribution or was modified by the maintainer?
To address this, a new feature has been added for language pack maintainers (who have the commit write access to the main repository). They can now commit the stage (attributing it fully to the contributor) but keep the committed strings staged. So they can first commit the whole contribution as-is and after that make corrections on top if it. In the log and the individual string's history, it is then clear what was submitted and how was it modified by the maintainer.