Since installing GIT Client plugin version 1.1 (and updated 1.1.1), Jenkins job now shows all changes since we started with GIT. See the attached picture (there is about 500 changes). It's quite annoying problem. All is OK after replacing the actual GIT Client plugin (1.1.1) with version 1.0.7. It's good workaround, but definitely not a permanent solution
The job we are using consists of two building slaves. And the interesting point is, that the change log looks fine on 64bit slave (only changes since the previous build are shown), but on 32bit slave (and Jenkins Master machine) it shows all changes since start.
Feel free to contact me in case you need more details.