another type check fix and add back a missing test

License: MIT
Signed-off-by: Jeromy <why@ipfs.io>

core/commands/config.go

@@ -290,7 +290,13 @@ func replaceConfig(r repo.Repo, file io.Reader) error {
 	if err != nil {
 		return fmt.Errorf("Failed to get PrivKey")
 	}
-	cfg.Identity.PrivKey = keyF.Value.(string)
+
+	pkstr, ok := keyF.Value.(string)
+	if !ok {
+		return fmt.Errorf("private key in config was not a string")
+	}
+
+	cfg.Identity.PrivKey = pkstr
 
 	return r.SetConfig(&cfg)
 }

test/sharness/t0021-config.sh

@@ -87,6 +87,10 @@ test_config_cmd() {
        test_expect_code 1 ipfs config Identity.PrivKey 2> ident_out
   '
 
+  test_expect_success "output looks good" '
+       test_cmp ident_exp ident_out
+  '
+
   test_expect_success "lower cased PrivKey" '
        sed -i -e '\''s/PrivKey/privkey/'\'' "$IPFS_PATH/config" &&
        test_expect_code 1 ipfs config Identity.privkey 2> ident_out