If we have a longer lasting feature branch, we should do regular merges from the develop onto the feature branch. Doing so all changes from develop are on the feature branch.
If using pull requests the commits for the merge operation are marked differently within Stash. However, within the diff view it is not possible to distinguish a change from a merge or a direct commit on the feature branch. To figure out the changes for the feature in fast manner, it would be very helpful if the changes introduced by the merge are marked differently.