Currently those actions starts from the first/last change if change is not selected (displayed as -/XX in diff dialog) or last selected change.

Common use case during refactoring: make many semi-related changes while refactor and then make several commits by select changes to commit from diff view. Each time when you stash particular change, the current change position is reset and you have to go thought all unrelated changes for current commit.

Assumed workflow:

• go from the first hunk to the last in the diff
• stage some hunk
• click to some place in the diff
• click to the Go to next change to move to the not yet processed hunk
  • currently: you go to the very first unstaged hunk