Disambiguating multiple formatted files when writing to standard output

When using google-java-format to format multiple files and print their formatted results to standard-out, it's unclear how I'm supposed to disambiguate between the results in the output. For performance reasons, I am running google-java-format against my codebase in batches of 100 files at a time, and for various other reasons, formatting in-place is not preferred.

For example, running this:

```shell
java -jar $HOME/bin/google-java-format --aosp path/to/file1.java path/to/file2.java path/to/file3.java path/to/file4.java
```

results in output like this:

```shell
/* my file 1 */

public class File1 {
// ...
}
/* my file 2 */

public class File2 {
// ...
}
/* my file 3 */

public class File3 {
// ...
}
/* my file 4 */

public class File4 {
// ...
}
```

This example is kind of contrived, but the main point is that the end of file1.java and the start of file2.java, and so on, are not delimited in a clear way. What can I do here to clearly associate the output for each formatted file with its source path?

從 issue 中所示的 google-java-format CLI 呼叫開始，著重於將多檔案格式化結果傳送至標準輸出的情況。確定一種明確的方法，將每個格式化結果與其來源路徑建立關聯，然後使用四檔案範例和等效的批次輸入驗證其行為。

由索引模型根據 Issue 內容生成。