In brief
git shortlog summarizes history by author and title. -s shows counts, while -n orders by those counts.
Useful to know
git shortlog summarizes history by author and title. -s shows counts, while -n orders by those counts. [1]
Use it to inspect a selected period rather than automatically judge quality. One large commit and many small ones have different granularity. Different author spellings may also need explicit mapping to avoid counting the same person separately.
Sources
For further detail and to check the information: