rev-list: inline `show_object_with_name()` in `show_object()`

rev-list: inline `show_object_with_name()` in `show_object()`

The `show_object_with_name()` function only has a single call site.
Inline call to `show_object_with_name()` in `show_object()` so the
explicit function can be cleaned up and live closer to where it is used.
While at it, factor out the code that prints the OID and newline for
both objects with and without a name. In a subsequent commit,
`show_object()` is modified to support printing object information in a
NUL-delimited format.

Signed-off-by: Justin Tobler <jltobler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>