improve git diff
improve git diff

Sometimes git does not print the name of the function being changed
after @@. It happens especially after a goto label which is not indented.
Giving a hint about the languages of files .c, .h and .py
will improve hunk headers of "git diff" rendering.

Signed-off-by: Thomas Monjalon <ee2fa8b2681c737f775687e475dcbf2028a412f1@6wind.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk