Merge branch 'jk/midx-write-v1-by-default' into jch

Avoid breaking older versions of Git and its reimplementations
by writing version 2 MIDX files by default.

* jk/midx-write-v1-by-default:
  MIDX: revert the default version to v1

Author: gitster

midx-write.c

@@ -1259,7 +1259,7 @@ static int write_midx_internal(struct write_midx_opts *opts)
 	struct tempfile *incr;
 	struct write_midx_context ctx = {
 		.preferred_pack_idx = NO_PREFERRED_PACK,
-		.version = MIDX_VERSION_V2,
+		.version = MIDX_VERSION_V1,
 	 };
 	struct multi_pack_index *midx_to_free = NULL;
 	int bitmapped_packs_concat_len = 0;

t/t5319-multi-pack-index.sh

@@ -19,9 +19,12 @@ midx_read_expect () {
 	NUM_CHUNKS=$3
 	OBJECT_DIR=$4
 	EXTRA_CHUNKS="$5"
+	# This reflects the default midx version we write; it should switch
+	# to 2 if we flip the default.
+	VERSION=1
 	{
 		cat <<-EOF &&
-		header: 4d494458 2 $HASH_LEN $NUM_CHUNKS $NUM_PACKS
+		header: 4d494458 $VERSION $HASH_LEN $NUM_CHUNKS $NUM_PACKS
 		chunks: pack-names oid-fanout oid-lookup object-offsets$EXTRA_CHUNKS
 		num_objects: $NUM_OBJECTS
 		packs:

t/t5335-compact-multi-pack-index.sh

@@ -57,6 +57,13 @@ test_midx_layer_object_uniqueness () {
 	done <$midx_chain
 }
 
+# MIDX compaction requires the v2 format, so make it the default
+# for the rest of this script. We check below that trying
+# compaction with v1 fails using "git -c", which will override this.
+test_expect_success 'set midx version config' '
+	git config --global midx.version 2
+'
+
 test_expect_success 'MIDX compaction with lex-ordered pack names' '
 	git init midx-compact-lex-order &&
 	(