oidset: refactor oidset_insert_from_set()

In a following commit, we will need to add all the oids from a set into
another set. In "list-objects-filter.c", there is already a static
function called add_all() to do that.

Let's rename this function oidset_insert_from_set() and move it into
oidset.{c,h} to make it generally available.

While at it, let's remove a useless `!= NULL`.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

list-objects-filter.c

@@ -711,15 +711,6 @@ static void filter_combine__free(void *filter_data)
 	free(d);
 }
 
-static void add_all(struct oidset *dest, struct oidset *src) {
-	struct oidset_iter iter;
-	struct object_id *src_oid;
-
-	oidset_iter_init(src, &iter);
-	while ((src_oid = oidset_iter_next(&iter)) != NULL)
-		oidset_insert(dest, src_oid);
-}
-
 static void filter_combine__finalize_omits(
 	struct oidset *omits,
 	void *filter_data)
@@ -728,7 +719,7 @@ static void filter_combine__finalize_omits(
 	size_t sub;
 
 	for (sub = 0; sub < d->nr; sub++) {
-		add_all(omits, &d->sub[sub].omits);
+		oidset_insert_from_set(omits, &d->sub[sub].omits);
 		oidset_clear(&d->sub[sub].omits);
 	}
 }

oidset.c

@@ -23,6 +23,16 @@ int oidset_insert(struct oidset *set, const struct object_id *oid)
 	return !added;
 }
 
+void oidset_insert_from_set(struct oidset *dest, struct oidset *src)
+{
+	struct oidset_iter iter;
+	struct object_id *src_oid;
+
+	oidset_iter_init(src, &iter);
+	while ((src_oid = oidset_iter_next(&iter)))
+		oidset_insert(dest, src_oid);
+}
+
 int oidset_remove(struct oidset *set, const struct object_id *oid)
 {
 	khiter_t pos = kh_get_oid_set(&set->set, *oid);

oidset.h

@@ -47,6 +47,12 @@ int oidset_contains(const struct oidset *set, const struct object_id *oid);
  */
 int oidset_insert(struct oidset *set, const struct object_id *oid);
 
+/**
+ * Insert all the oids that are in set 'src' into set 'dest'; a copy
+ * is made of each oid inserted into set 'dest'.
+ */
+void oidset_insert_from_set(struct oidset *dest, struct oidset *src);
+
 /**
  * Remove the oid from the set.
  *