test(core): backup round-trips git archive + size check

crates/relicario-core/tests/backup.rs

@@ -104,3 +104,30 @@ fn round_trip_with_reference_image() {
     assert_eq!(unpacked.reference_jpg.as_deref(), Some(jpg_bytes.as_slice()));
     assert!(unpacked.git_archive.is_none());
 }
+
+#[test]
+fn round_trip_with_git_archive() {
+    let tar_bytes: Vec<u8> = b"FAKE TAR BYTES; core treats opaquely".repeat(50);
+    let mut input = empty_input();
+    input.git_archive = Some(&tar_bytes);
+
+    let out = pack_backup(input, "p").unwrap();
+    let unpacked = unpack_backup(&out, "p").unwrap();
+
+    assert_eq!(unpacked.git_archive.as_deref(), Some(tar_bytes.as_slice()));
+}
+
+#[test]
+fn no_history_produces_strict_subset() {
+    let mut a = empty_input();
+    a.git_archive = Some(b"some-tar-bytes");
+    let with = pack_backup(a, "p").unwrap();
+
+    let without = pack_backup(empty_input(), "p").unwrap();
+
+    // The "without" file is strictly smaller (one fewer base64-encoded blob in JSON).
+    assert!(without.len() < with.len(),
+        "no-history backup should be smaller: with={}, without={}",
+        with.len(), without.len()
+    );
+}