diffstat can refer to the diffstat program, or to git diff --stat output; use this tag for questions about either.
See https://invisible-island.net/diffstat/ for the history of the diffstat program.  Git's diff --stat is based on the same general idea: that, given some sort of patch, we'd like a summary of changes that the patch makes: what files are affected, and to what extent.
 
     
     
     
     
     
     
     
     
     
     
     
    