fix: binary file corruption (#230)

* fix: image commits leads to invalid images

**Location:** `src/blob.ts`, line 28

The code was reading files with UTF-8 text encoding:
```typescript
fs.createReadStream(this.absolutePath, { encoding: 'utf8' })
```

Images are **binary files** containing arbitrary byte values (0-255). The UTF-8 encoding option tells Node.js to:
1. Interpret the binary data as UTF-8 text
2. Drop any byte sequences that are not valid UTF-8

This causes data loss because:
- Valid UTF-8 sequences are 1-4 bytes depending on the character
- Many byte combinations in binary files are invalid UTF-8 sequences
- These invalid bytes are silently dropped by the UTF-8 decoder
- The resulting file is corrupted (missing bytes)

* fix: prevent binary file corruption when encoding to base64

The base64-encoder was converting base64 strings back to buffers before
pushing them to the stream, which caused them to be re-encoded as UTF-8
bytes. This corrupted binary files (images, PDFs, etc.) when they were
committed and pushed to GitHub.

Changes:
- base64-encoder.ts: Push base64 strings directly instead of converting
  them back to buffers. This prevents the double-encoding that was
  corrupting binary data.
- blob.ts: Remove UTF-8 encoding from file stream reading. Files are now
  read as raw buffers, which is necessary for the base64 encoder to work
  correctly with both text and binary files.

The fix ensures that:
- Binary files (PNG, JPG, PDF, etc.) are encoded without corruption
- Text files continue to work correctly
- The action properly base64 encodes file content for GitHub API

Fixes image corruption when committing and pushing images to GitHub

* fix: add binary regression tests to Base64Encoder and Blob.load() using a fixture with non-UTF-8 byte sequences to guard against silent data corruption

* chore: update bundle dist

---------

Co-authored-by: Joris Conijn <joris@conijnonline.nl>

Author: ryancyq

__tests__/blob.test.ts

@@ -72,6 +72,16 @@ describe('Blob', () => {
       )
     })
 
+    it('binary file without corruption', async () => {
+      const blob = getBlob('fixtures/blob.bin')
+      const fileAddition = await blob.load()
+      expect(fileAddition.contents).toEqual(
+        fs
+          .readFileSync(join(__dirname, 'fixtures/blob.bin.base64.txt'))
+          .toString()
+      )
+    })
+
     it('file with string', async () => {
       const blob = getBlob('fixtures/error.txt')
       const mockStream = new PassThrough()

__tests__/fixtures/blob.bin

@@ -0,0 +1 @@
+iVBORw0KGgr//gAB

__tests__/fixtures/blob.bin.base64.txt

@@ -15,4 +15,18 @@ describe('Base64 Encoder', () => {
     const streamedContent = Buffer.concat(chunks).toString('utf8')
     expect(streamedContent).toEqual(Buffer.from(content).toString('base64'))
   })
+
+  it('binary stream without corruption', async () => {
+    const binary = Buffer.from([
+      0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a, 0xff, 0xfe, 0x00, 0x01,
+    ])
+    const stream = Readable.from(binary).pipe(new Base64Encoder())
+
+    const chunks: Buffer[] = []
+    for await (const chunk of stream) {
+      chunks.push(Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk))
+    }
+    const streamedContent = Buffer.concat(chunks).toString('utf8')
+    expect(streamedContent).toEqual(binary.toString('base64'))
+  })
 })

__tests__/stream/base64-encoder.test.ts

@@ -23957,12 +23957,12 @@ var Base64Encoder = class extends Transform {
       chunk = chunk.subarray(0, chunk.length - overflowSize);
     }
     const base64String = chunk.toString("base64");
-    this.push(Buffer2.from(base64String));
+    this.push(base64String);
     callback();
   }
   _flush(callback) {
     if (this.overflow) {
-      this.push(Buffer2.from(this.overflow.toString("base64")));
+      this.push(this.overflow.toString("base64"));
     }
     callback();
   }
@@ -23979,7 +23979,7 @@ var Blob2 = class {
     if (!fs.existsSync(this.absolutePath)) {
       throw new Error(`File does not exist, path: ${this.absolutePath}`);
     }
-    return fs.createReadStream(this.absolutePath, { encoding: "utf8" }).pipe(new Base64Encoder());
+    return fs.createReadStream(this.absolutePath).pipe(new Base64Encoder());
   }
   async load() {
     const chunks = [];

dist/index.js

@@ -26,9 +26,7 @@ export class Blob {
       throw new Error(`File does not exist, path: ${this.absolutePath}`)
     }
 
-    return fs
-      .createReadStream(this.absolutePath, { encoding: 'utf8' })
-      .pipe(new Base64Encoder())
+    return fs.createReadStream(this.absolutePath).pipe(new Base64Encoder())
   }
 
   async load(): Promise<FileAddition> {

src/blob.ts

@@ -25,13 +25,13 @@ export default class Base64Encoder extends Transform {
     }
 
     const base64String = chunk.toString('base64')
-    this.push(Buffer.from(base64String))
+    this.push(base64String)
     callback()
   }
 
   _flush(callback: TransformCallback): void {
     if (this.overflow) {
-      this.push(Buffer.from(this.overflow.toString('base64')))
+      this.push(this.overflow.toString('base64'))
     }
     callback()
   }