  In large and active software projects, it becomes impractical for a developer
to stay aware of all project activity. While it might not be necessary to know
about each commit or issue, it is arguably important to know about the ones
that are unusual. To investigate this hypothesis, we identified unusual events
in 200 GitHub projects using a comprehensive list of ways in which an artifact
can be unusual and asked 140 developers responsible for or affected by these
events to comment on the usefulness of the corresponding information. Based on
2,096 answers, we identify the subset of unusual events that developers
consider particularly useful, including large code modifications and unusual
amounts of reviewing activity, along with qualitative evidence on the reasons
behind these answers. Our findings provide a means for reducing the amount of
information that developers need to parse in order to stay up to date with
development activity in their projects.
