add test for handling comment garbage

tests/zip_comment_garbage.rs

@@ -0,0 +1,30 @@
+// Some zip files can contain garbage after the comment. For example, python zipfile generates
+// it when opening a zip in 'a' mode:
+//
+// >>> from zipfile import ZipFile
+// >>> with ZipFile('comment_garbage.zip', 'a') as z:
+// ...     z.comment = b'long comment bla bla bla'
+// ...
+// >>> with ZipFile('comment_garbage.zip', 'a') as z:
+// ...     z.comment = b'short.'
+// ...
+// >>>
+//
+// Hexdump:
+//
+// 00000000  50 4b 05 06 00 00 00 00  00 00 00 00 00 00 00 00  |PK..............|
+// 00000010  00 00 00 00 06 00 73 68  6f 72 74 2e 6f 6d 6d 65  |......short.omme|
+// 00000020  6e 74 20 62 6c 61 20 62  6c 61 20 62 6c 61        |nt bla bla bla|
+// 0000002e
+
+use std::io;
+use zip::ZipArchive;
+
+#[test]
+fn correctly_handle_zip_with_garbage_after_comment() {
+    let mut v = Vec::new();
+    v.extend_from_slice(include_bytes!("../tests/data/comment_garbage.zip"));
+    let archive = ZipArchive::new(io::Cursor::new(v)).expect("couldn't open test zip file");
+
+    assert_eq!(archive.comment(), "short.".as_bytes());
+}