Merge branch 'tb/midx-write-corrupt-checksum-fix' into jch

The logic that avoids reusing MIDX files with a wrong checksum was
broken, which has been corrected.

* tb/midx-write-corrupt-checksum-fix:
  midx-write.c: assume checksum-invalid MIDXs require an update
  t/t5319-multi-pack-index.sh: drop early 'test_done'

midx-write.c

@@ -1011,6 +1011,20 @@ static bool midx_needs_update(struct multi_pack_index *midx, struct write_midx_c
 	struct strbuf buf = STRBUF_INIT;
 	bool needed = true;
 
+	/*
+	 * Ensure that we have a valid checksum before consulting the
+	 * exisiting MIDX in order to determine if we can avoid an
+	 * update.
+	 *
+	 * This is necessary because the given MIDX is loaded directly
+	 * from the object store (because we still compare our proposed
+	 * update to any on-disk MIDX regardless of whether or not we
+	 * have assigned "ctx.m") and is thus not guaranteed to have a
+	 * valid checksum.
+	 */
+	if (!midx_checksum_valid(midx))
+		goto out;
+
 	/*
 	 * Ignore incremental updates for now. The assumption is that any
 	 * incremental update would be either empty (in which case we will bail

t/t5319-multi-pack-index.sh

@@ -415,8 +415,6 @@ test_expect_success 'up-to-date multi-pack-index is retained' '
 	)
 '
 
-test_done
-
 test_expect_success 'verify multi-pack-index success' '
 	git multi-pack-index verify --object-dir=$objdir
 '