This function asks for the value of a configuration and after
using the value does not have to retain ownership of it.
git_config_get_string_const() however is a function to get a
copy of the value, but we forget to free it before we return.
Signed-off-by: Stefan Beller <sbeller@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>