git log anomalities

Hello,

today I looked at the changes to drivers/net/ethernet/freescale/fec.c in the kernel since v3.8 using

	git log --stat v3.8.. --full-diff -- drivers/net/ethernet/freescale/fec.c

which looks as expected. But when I added --graph the diffstats change. E.g. for 793fc0964be1921f15a44be58b066f22b925d90b it changes from:

 drivers/net/ethernet/freescale/Makefile   |    3 +-
 drivers/net/ethernet/freescale/fec.c      | 1966 -----------------------------
 drivers/net/ethernet/freescale/fec_main.c | 1966 +++++++++++++++++++++++++++++
 drivers/net/ethernet/freescale/fec_ptp.c  |    3 -
 4 files changed, 1968 insertions(+), 1970 deletions(-)

to

|  Documentation/devicetree/bindings/net/dsa/dsa.txt |   91 +
|  .../bindings/net/marvell-orion-mdio.txt           |    3 +
|  Documentation/networking/ip-sysctl.txt            |   35 +-
|  MAINTAINERS                                       |    2 +-
|  arch/arm/net/bpf_jit_32.c                         |    5 +-
|  arch/arm/plat-orion/common.c                      |   54 +-
|  arch/powerpc/net/bpf_jit_comp.c                   |   12 +-
|  ...
|  404 files changed, 15373 insertions(+), 8563 deletions(-)

Is that a bug, or a feature I don't understand?

(I'm using Debian's 1:1.8.3.2-1)

Best regards Uwe