git: update to v2.7.0

Update to git version v2.7.0.

* Upstream commit ed1c9977cb1b63e4270ad8bdf967a2d02580aa08 (Remove
  get_object_hash.) changed API:

  Convert all instances of get_object_hash to use an appropriate
  reference to the hash member of the oid member of struct object.
  This provides no functional change, as it is essentially a macro
  substitution.

Signed-off-by: Christian Hesse <mail@eworm.de>

ui-shared.c

@@ -525,7 +525,7 @@ void cgit_object_link(struct object *obj)
 {
 	char *page, *shortrev, *fullrev, *name;
 
-	fullrev = sha1_to_hex(obj->sha1);
+	fullrev = oid_to_hex(&obj->oid);
 	shortrev = xstrdup(fullrev);
 	shortrev[10] = '\0';
 	if (obj->type == OBJ_COMMIT) {