[readFile]: compatible like node:fs

Author: tachibana-shin

index.d.ts

@@ -47,7 +47,8 @@ declare module '@isomorphic-git/lightning-fs' {
 
     writeFile(filepath: string, data: Uint8Array | string, options: FS.WriteFileOptions | undefined | string, cb: (err: Error) => void): void
 
-    readFile(filepath: string, options: FS.ReadFileOptions | undefined | string, cb: (err: Error, data: Uint8Array | string) => void): void
+    readFile(filepath: string, options: 'utf8' | { encoding: 'utf8' }, cb: (err: Error, data: string) => void): void
+    readFile(filepath: string, options: {} | void, cb: (err: Error, data: Uint8Array) => void): void
 
     /**
      * Delete a file
@@ -149,7 +150,7 @@ declare module '@isomorphic-git/lightning-fs' {
 
       writeFile(filepath: string, data: Uint8Array | string, options?: FS.WriteFileOptions | string): Promise<void>
 
-      readFile(filepath: string, options: { encoding: 'utf8' }): Promise<string>
+      readFile(filepath: string, options: 'utf8' | { encoding: 'utf8' }): Promise<string>
       readFile(filepath: string, options?: {}): Promise<Uint8Array>
 
       /**

src/DefaultBackend.js

@@ -95,7 +95,7 @@ module.exports = class DefaultBackend {
     return this._cache.writeStat(filepath, size, opts)
   }
   async readFile(filepath, opts) {
-    const { encoding } = opts;
+    const encoding = typeof opts === "string" ? opts : opts?.encoding;
     if (encoding && encoding !== 'utf8') throw new Error('Only "utf8" encoding is supported in readFile');
     let data = null, stat = null
     try {