Update to git version v2.5.0.
* Upstream commit 5455ee0573a22bb793a7083d593ae1ace909cd4c (Merge branch
'bc/object-id') changed API:
for_each_ref() callback functions were taught to name the objects
not with "unsigned char sha1[20]" but with "struct object_id".
* Upstream commit dcf692625ac569fefbe52269061230f4fde10e47 (path.c: make
get_pathname() call sites return const char *)
Signed-off-by: Christian Hesse <mail@eworm.de>