jenkinsci/git-plugin — pull request #70 by blatinville (2012-05-22 09:10:13+00:00)
Title: git show shall compare with last build sha1

use git show --no-abbrev --format=raw -M --raw 'old sha1'..'new sha1'
instead of
git show --no-abbrev --format=raw -M --raw 'new sha1'

This is the correction for
"Git plug-in & included regions : build not triggered in case of mutiple commits in one push."
https://issues.jenkins-ci.org/browse/JENKINS-13368.

I think think this correction also solves
"git plugin "included regions" feature is bypassed when evaluating a merge commit"
https://issues.jenkins-ci.org/browse/JENKINS-13580

We shall find a common correction for both issues are they are linked to include region feature.