sha1-name.c: add `get_oidf()` which acts like `get_oid()`
Compared to `get_oid()`, `get_oidf()` has as parameters
a pointer to `object_id`, a printf format string and
additional arguments. This will help simplify the code
in subsequent commits.
Original-idea-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Paul-Sebastian Ungureanu <ungureanupaulsebastian@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>