refactor: add copy method to CompressionEngineProgram

src/compression/program.rs

@@ -77,6 +77,13 @@ impl CompressionEngine for CompressionEngineProgram {
 
         Ok(Box::new(process.stdin.unwrap()))
     }
+
+    fn copy(&self, file_path: PathBuf, writer: &mut dyn Write) -> Result<()> {
+        let mut reader = self.open(file_path)?;
+        io::copy(&mut reader, writer)?;
+        writer.flush()?;
+        Ok(())
+    }
 }
 
 fn get_program_path(program: &str) -> Result<String> {