t-reftable-record: add index tests for reftable_record_is_deletion()

reftable_record_is_deletion() is a function defined in
reftable/record.{c, h} that determines whether a record is of
type deletion or not. In the current testing setup, this function
is left untested for index records.

Add tests for this function in the case of index records.
Note that since index records cannot be of type deletion, this function
must always return '0' when called on an index record.

Mentored-by: Patrick Steinhardt <[email protected]>
Mentored-by: Christian Couder <[email protected]>
Signed-off-by: Chandra Pratap <[email protected]>
Acked-by: Karthik Nayak <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: Chandra Pratap

t/unit-tests/t-reftable-record.c

@@ -466,6 +466,7 @@ static void t_reftable_index_record_roundtrip(void)
 	reftable_record_key(&in, &key);
 	t_copy(&in);
 
+	check(!reftable_record_is_deletion(&in));
 	check(!strbuf_cmp(&key, &in.u.idx.last_key));
 	n = reftable_record_encode(&in, dest, GIT_SHA1_RAWSZ);
 	check_int(n, >, 0);