fix(v2): truncate docuhash return value in order to avoid ERRNAMETOOLONG error (#4899)

* fix: truncate docuhash return value in order to avoid ERRNAMETOOLONG error

* chore: add deep file path test page to website

* refactor: reorganize docuHash/pathUtils code and tests

* chore: git support longpaths on v2 windows tests workflow

Co-authored-by: slorber <lorber.sebastien@gmail.com>

packages/docusaurus-utils/src/pathUtils.ts

@@ -0,0 +1,48 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+// Based on https://github.com/gatsbyjs/gatsby/pull/21518/files
+
+import {createHash} from 'crypto';
+
+// MacOS (APFS) and Windows (NTFS) filename length limit = 255 chars, Others = 255 bytes
+const MAX_PATH_SEGMENT_CHARS = 255;
+const MAX_PATH_SEGMENT_BYTES = 255;
+// Space for appending things to the string like file extensions and so on
+const SPACE_FOR_APPENDING = 10;
+
+const isMacOs = process.platform === `darwin`;
+const isWindows = process.platform === `win32`;
+
+export const isNameTooLong = (str: string): boolean => {
+  return isMacOs || isWindows
+    ? str.length + SPACE_FOR_APPENDING > MAX_PATH_SEGMENT_CHARS // MacOS (APFS) and Windows (NTFS) filename length limit (255 chars)
+    : Buffer.from(str).length + SPACE_FOR_APPENDING > MAX_PATH_SEGMENT_BYTES; // Other (255 bytes)
+};
+
+export const shortName = (str: string): string => {
+  if (isMacOs || isWindows) {
+    const overflowingChars = str.length - MAX_PATH_SEGMENT_CHARS;
+    return str.slice(
+      0,
+      str.length - overflowingChars - SPACE_FOR_APPENDING - 1,
+    );
+  }
+  const strBuffer = Buffer.from(str);
+  const overflowingBytes =
+    Buffer.byteLength(strBuffer) - MAX_PATH_SEGMENT_BYTES;
+  return strBuffer
+    .slice(
+      0,
+      Buffer.byteLength(strBuffer) - overflowingBytes - SPACE_FOR_APPENDING - 1,
+    )
+    .toString();
+};
+
+export function simpleHash(str: string, length: number): string {
+  return createHash('md5').update(str).digest('hex').substr(0, length);
+}