Thanks for the clarification. I appreciate it very much!
Command line git 1.7.1 lacks many of the basic features needed to support the Jenkins git plugin. The Jenkins git plugin wiki page notes that the earliest supported version is git 1.7.10. Even that version has cases in the git plugin source code which can't be supported due to missing features. The best supported command line git versions for the Jenkins git plugin begin with 1.9 and continue through command line git 2.20 (the current release).
Command line git 1.7.1 was released over 8 years ago. It is a very old version of command line git.
You can switch to use JGit as the implementation instead of command line git in many cases and that will provide the correct changes output. There are known cases where JGit does not support a use case that command line git supports. Thus, "switch to JGit" is not always available as an option.
You can install a newer version of command line git on your CentOS 6 machines. See the stackoverflow article for one technique.
You can switch back to Jenkins git plugin 3.9.x and git client plugin 2.7.x. That will remove several bug fixes but gives support for this case with command line git 1.7.1.