sha1-file: drop has_sha1_file()

sha1-file: drop has_sha1_file()

There are no callers left of has_sha1_file() or its with_flags()
variant. Let's drop them, and convert has_object_file() from a wrapper
into the "real" function. Ironically, the sha1 variant was just copying
into an object_id internally, so the resulting code is actually shorter!

We can also drop the coccinelle rules for catching has_sha1_file()
callers. Since the function no longer exists, the compiler will do that
for us.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>