Subsystem maintainers routinely use git
request-pull as part of the
process of sending work upstream. Normally, the result includes a list of
commits included in the request and a nice
diffstat that shows which files will be touched and how much of each will
be changed; examples
abound on the kernel mailing lists. Occasionally, though, a repository with a relatively
complicated development history will yield a massive diffstat containing a
great deal of unrelated work. The result looks ugly and obscures what the
pull request is actually doing. This document describes what is happening
and how to fix things up; it is derived from The Wisdom of Linus Torvalds,
which has been posted numerous times over the years (example 1,
example 2).

Source: LWN.net – [$] Handling messy pull-request diffstats