Add Error::source implementation

Fixes #2

src/main.rs

@@ -58,7 +58,17 @@ impl fmt::Display for Error {
     }
 }
 
-impl error::Error for Error {}
+impl error::Error for Error {
+    fn source(&self) -> Option<&(dyn error::Error + 'static)> {
+        match self {
+            Error::Bootconfig(e) => Some(e),
+            Error::DiskImage(e) => Some(e),
+            Error::Partitions(e) => Some(e),
+            Error::TransformSparse(e) => Some(e),
+            Error::Uboot(e) => Some(e),
+            Error::Vbmeta(e) => Some(e),        }
+    }
+}
 
 #[derive(Parser)]
 #[command(author, version, about, long_about = None)]