sha1-name.c: add `get_oidf()` which acts like `get_oid()`

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 <redacted>
Signed-off-by: Paul-Sebastian Ungureanu <redacted>
Signed-off-by: Junio C Hamano <redacted>