Validate migration files (#18203)

JSON Schema validation for data used by Gitea during migrations

Discussion at https://forum.forgefriends.org/t/common-json-schema-for-repository-information/563

Co-authored-by: Loïc Dachary <loic@dachary.org>

modules/migration/schemas_dynamic.go

@@ -0,0 +1,40 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+//go:build !bindata
+// +build !bindata
+
+package migration
+
+import (
+	"io"
+	"net/url"
+	"os"
+	"path"
+	"path/filepath"
+)
+
+func openSchema(s string) (io.ReadCloser, error) {
+	u, err := url.Parse(s)
+	if err != nil {
+		return nil, err
+	}
+	basename := path.Base(u.Path)
+	filename := basename
+	//
+	// Schema reference each other within the schemas directory but
+	// the tests run in the parent directory.
+	//
+	if _, err := os.Stat(filename); os.IsNotExist(err) {
+		filename = filepath.Join("schemas", basename)
+		//
+		// Integration tests run from the git root directory, not the
+		// directory in which the test source is located.
+		//
+		if _, err := os.Stat(filename); os.IsNotExist(err) {
+			filename = filepath.Join("modules/migration/schemas", basename)
+		}
+	}
+	return os.Open(filename)
+}