upgrade: reset world dependencies during traversal

This allows us to get apk-tools dependencies get reset at proper
time in world. As a bonus, it reduces code amount.

src/state.c

@@ -138,14 +138,20 @@ static struct apk_name_choices *name_choices_new(struct apk_database *db,
 		if (dep->name != name)
 			continue;
 
-		for (j = 0; j < nc->num; ) {
-			if (apk_dep_is_satisfied(dep, nc->pkgs[j])) {
-				j++;
-			} else {
-				nc->pkgs[j] = nc->pkgs[nc->num - 1];
-				nc->num--;
+		if (apk_flags & APK_PREFER_AVAILABLE) {
+			dep->version = apk_blob_atomize(APK_BLOB_NULL);
+			dep->result_mask = APK_DEPMASK_REQUIRE;
+		} else {
+			for (j = 0; j < nc->num; ) {
+				if (apk_dep_is_satisfied(dep, nc->pkgs[j])) {
+					j++;
+				} else {
+					nc->pkgs[j] = nc->pkgs[nc->num - 1];
+					nc->num--;
+				}
 			}
 		}
+		break;
 	}
 
 	return nc;

src/upgrade.c

@@ -33,21 +33,10 @@ static int upgrade_parse(void *ctx, struct apk_db_options *dbopts,
 int apk_do_self_upgrade(struct apk_database *db, struct apk_state *state)
 {
 	struct apk_dependency dep;
-	int r, i;
+	int r;
 
 	apk_dep_from_blob(&dep, db, APK_BLOB_STR("apk-tools"));
 
-	if (apk_flags & APK_PREFER_AVAILABLE) {
-		for (i = 0; i < db->world->num; i++) {
-			struct apk_dependency *dep0 = &db->world->item[i];
-			if (dep0->name != dep.name)
-				continue;
-			dep0->version = apk_blob_atomize(APK_BLOB_NULL);
-			dep0->result_mask = APK_DEPMASK_REQUIRE;
-			break;
-		}
-	}
-
 	r = apk_state_lock_dependency(state, &dep);
 	if (r != 0 || state->num_changes == 0)
 		return r;
@@ -74,7 +63,6 @@ static int upgrade_main(void *ctx, struct apk_database *db, int argc, char **arg
 {
 	struct apk_state *state = NULL;
 	struct apk_name_array *missing;
-	apk_blob_t *null_atom = apk_blob_atomize(APK_BLOB_NULL);
 	int i, r = 0;
 
 	apk_flags |= APK_UPGRADE;
@@ -92,11 +80,7 @@ static int upgrade_main(void *ctx, struct apk_database *db, int argc, char **arg
 
 	for (i = 0; i < db->world->num; i++) {
 		struct apk_dependency *dep = &db->world->item[i];
-		if (dep->version != null_atom &&
-		    (apk_flags & APK_PREFER_AVAILABLE)) {
-			dep->result_mask = APK_DEPMASK_REQUIRE;
-			dep->version = null_atom;
-		}
+
 		if (dep->name->pkgs->num != 0)
 			r |= apk_state_lock_dependency(state, dep);
 		else