fix: prepend line origin chars in diff.print() output

docs/ko/reference/Diff/Methods/print.md

@@ -2,6 +2,8 @@
 
 포맷된 텍스트 출력을 생성하며 diff를 순회해요.
 
+출력은 `git diff`를 따릅니다. `Patch`와 `PatchId` 포맷에서는 각 본문 줄 앞에 origin이 붙어요. 추가 줄은 `+`, 삭제 줄은 `-`, 컨텍스트 줄은 공백 한 칸이에요. 파일 헤더, hunk 헤더(`@@ ... @@`), binary 안내, `\ No newline at end of file` 마커는 그대로 출력돼요.
+
 ## 시그니처
 
 ```ts
@@ -16,7 +18,7 @@ class Diff {
   <li class="param-li param-li-root">
     <span class="param-name">options</span><span class="param-type">null | DiffPrintOptions</span>
     <br>
-    <p class="param-description">츌력에 사용할 옵션이에요.</p>
+    <p class="param-description">출력에 사용할 옵션이에요.</p>
     <ul class="param-ul">
       <li class="param-li">
         <span class="param-name">format</span><span class="param-type">DiffFormat</span>
@@ -33,6 +35,20 @@ class Diff {
   <li class="param-li param-li-root">
     <span class="param-type">string</span>
     <br>
-    <p class="param-description">포맷팅된 출력 값을 반환해요.</p>
+    <p class="param-description">포맷팅된 출력 값을 반환해요. 기본 <code>Patch</code> 포맷이면 <code>git diff</code>와 같은 unified patch예요.</p>
   </li>
 </ul>
+
+### 예제
+
+```ts
+const diff = repo.diffIndexToWorkdir();
+console.log(diff.print());
+// diff --git a/A b/A
+// index f70f10e..784f93d 100644
+// --- a/A
+// +++ b/A
+// @@ -1 +1 @@
+// -A
+// +A modified
+```

docs/ko/usage/diff.md

@@ -82,16 +82,15 @@ console.log(diff.print());
  * --- a/first
  * +++ b/first
  * @@ -1 +1,2 @@
- * first
- * first modified
- *
+ *  first
+ * +first modified
  * diff --git a/second b/second
  * deleted file mode 100644
  * index e019be0..0000000
  * --- a/second
  * +++ /dev/null
  * @@ -1 +0,0 @@
- * second
+ * -second
  */
 ```
 

docs/reference/Diff/Methods/print.md

@@ -2,6 +2,8 @@
 
 Iterate over a diff generating formatted text output.
 
+The output follows `git diff`. For the `Patch` and `PatchId` formats, each content line is prefixed with its origin: `+` for an added line, `-` for a deleted line and a single space for a context line. File headers, hunk headers (`@@ ... @@`), binary notices and `\ No newline at end of file` markers are emitted as-is.
+
 ## Signature
 
 ```ts
@@ -33,6 +35,20 @@ class Diff {
   <li class="param-li param-li-root">
     <span class="param-type">string</span>
     <br>
-    <p class="param-description">Formatted text output.</p>
+    <p class="param-description">Formatted text output. With the default <code>Patch</code> format, this is a unified patch like <code>git diff</code>.</p>
   </li>
 </ul>
+
+### Examples
+
+```ts
+const diff = repo.diffIndexToWorkdir();
+console.log(diff.print());
+// diff --git a/A b/A
+// index f70f10e..784f93d 100644
+// --- a/A
+// +++ b/A
+// @@ -1 +1 @@
+// -A
+// +A modified
+```

docs/usage/diff.md

@@ -80,16 +80,15 @@ console.log(diff.print());
  * --- a/first
  * +++ b/first
  * @@ -1 +1,2 @@
- * first
- * first modified
- *
+ *  first
+ * +first modified
  * diff --git a/second b/second
  * deleted file mode 100644
  * index e019be0..0000000
  * --- a/second
  * +++ /dev/null
  * @@ -1 +0,0 @@
- * second
+ * -second
  */
 ```
 

src/diff.rs

@@ -366,6 +366,12 @@ impl Diff {
   #[napi]
   /// Iterate over a diff generating formatted text output.
   ///
+  /// The output follows `git diff`. For the `Patch` and `PatchId` formats, each
+  /// content line is prefixed with its origin: `+` for an added line, `-` for a
+  /// deleted line and a single space for a context line. File headers, hunk
+  /// headers (`@@ ... @@`), binary notices and `\ No newline at end of file`
+  /// markers are emitted as-is.
+  ///
   /// @category Diff/Methods
   /// @signature
   /// ```ts
@@ -375,13 +381,33 @@ impl Diff {
   /// ```
   ///
   /// @param {DiffPrintOptions} [options] - Print options for diff.
-  /// @returns Formatted text output.
+  /// @returns Formatted text output. With the default `Patch` format, this is a unified patch like `git diff`.
+  /// @example
+  /// ```ts
+  /// const diff = repo.diffIndexToWorkdir();
+  /// console.log(diff.print());
+  /// // diff --git a/A b/A
+  /// // index f70f10e..784f93d 100644
+  /// // --- a/A
+  /// // +++ b/A
+  /// // @@ -1 +1 @@
+  /// // -A
+  /// // +A modified
+  /// ```
   pub fn print(&self, options: Option<DiffPrintOptions>) -> String {
     let format = options.and_then(|x| x.format).unwrap_or_default();
     let mut lines: Vec<String> = vec![];
     let _ = self.inner.print(format.into(), |_delta, _hunk, line| {
       if let Ok(content) = std::str::from_utf8(line.content()) {
-        lines.push(content.to_string());
+        let origin = line.origin();
+        match origin {
+          ' ' | '+' | '-' => {
+            lines.push(format!("{}{}", origin, content));
+          }
+          _ => {
+            lines.push(content.to_string());
+          }
+        }
       }
       true
     });

tests/diff.spec.ts

@@ -163,16 +163,16 @@ index f70f10e..784f93d 100644
 --- a/A
 +++ b/A
 @@ -1 +1 @@
-A
-A modified
+-A
++A modified
 \\ No newline at end of file
 diff --git a/B b/B
 deleted file mode 100644
 index 223b783..0000000
 --- a/B
 +++ /dev/null
 @@ -1 +0,0 @@
-B
+-B
 `);
     expect(diff.print({ format: 'PatchHeader' })).toEqual(`diff --git a/A b/A
 index f70f10e..784f93d 100644