[PATCH v2] upload-pack: swap wanted-ref/shallow-info responses

[Royce Remer <royceremer@gmail.com>]

When a server enables uploadpack.allowRefInWant, upload_pack_v2()
sends wanted-ref info before shallow-info.  The fetch-pack client
expects shallow-info first; receiving them out of order causes it
to exit:

    fatal: expected 'packfile', received 'shallow-info'

This error condition only applies to protocol v2 clients performs
a shallow fetch (--depth) against servers with allowRefInWant
configured.

Swap the send order so that upload_pack_v2() sends shallow-info
before wanted-ref info.  This is a server-side-only change and is
compatible with all existing client versions.

Signed-off-by: Royce Remer <royceremer@gmail.com>
---
 t/t5703-upload-pack-ref-in-want.sh | 18 ++++++++++++++++++
 upload-pack.c                      |  2 +-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/t/t5703-upload-pack-ref-in-want.sh b/t/t5703-upload-pack-ref-in-want.sh
index 249137b467..9e2a090c9e 100755
--- a/t/t5703-upload-pack-ref-in-want.sh
+++ b/t/t5703-upload-pack-ref-in-want.sh
@@ -295,6 +295,24 @@ test_expect_success 'fetching with wildcard that matches multiple refs' '
 	grep "want-ref refs/heads/o/bar" log
 '
 
+test_expect_success 'shallow clone with ref-in-want' '
+       rm -rf local &&
+       GIT_TEST_PROTOCOL_VERSION=2 git clone --depth=1 "file://$REPO" local &&
+       git -C "$REPO" rev-parse main >expected &&
+       git -C local rev-parse refs/remotes/origin/main >actual &&
+       test_cmp expected actual &&
+       git -C local log --oneline refs/remotes/origin/main >log &&
+       test_line_count = 1 log
+'
+
+test_expect_success 'incremental shallow fetch with ref-in-want' '
+       rm -rf local &&
+       GIT_TEST_PROTOCOL_VERSION=2 git clone --depth=1 "file://$REPO" local &&
+       GIT_TEST_PROTOCOL_VERSION=2 git -C local fetch --depth=2 origin main &&
+       git -C local log --oneline refs/remotes/origin/main >log &&
+       test_line_count = 2 log
+'
+
 REPO="$(pwd)/repo-ns"
 
 test_expect_success 'setup namespaced repo' '
diff --git a/upload-pack.c b/upload-pack.c
index a52856d869..a70d237ad3 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -1812,8 +1812,8 @@ int upload_pack_v2(struct repository *r, struct packet_reader *request)
 				state = UPLOAD_DONE;
 			break;
 		case UPLOAD_SEND_PACK:
-			send_wanted_ref_info(&data);
 			send_shallow_info(&data);
+			send_wanted_ref_info(&data);
 
 			if (data.uri_protocols.nr) {
 				create_pack_file(&data, &data.uri_protocols);

base-commit: e9019fcafe0040228b8631c30f97ae1adb61bcdc
-- 
2.55.0.1.ga30d533ec0