[PATCH v6 3/6] http: accept HTTP 416 for complete partial packs

A resumed pack request may already have all bytes of the remote pack.
A server can respond to the resulting Range request with HTTP 416
instead of returning an empty response.

Accept that response in each pack-download caller and let index-pack
validate the completed staging file. This can happen without concurrent
downloads when a previous attempt completed the transfer but failed
before indexing it.

Add a regression test that seeds a complete partial pack and checks that
http-fetch indexes it after the server returns HTTP 416.

Signed-off-by: Ted Nyman <[email protected]>
---
 http-fetch.c               |  3 ++-
 http-push.c                |  3 ++-
 http-walker.c              |  3 ++-
 t/t5550-http-fetch-dumb.sh | 19 +++++++++++++++++++
 4 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/http-fetch.c b/http-fetch.c
index 601a77c3c1..05f68f306a 100644
--- a/http-fetch.c
+++ b/http-fetch.c
@@ -70,7 +70,8 @@ static void fetch_single_packfile(struct object_id *packfile_hash,
 
 	if (start_active_slot(preq->slot)) {
 		run_active_slot(preq->slot);
-		if (results.curl_result != CURLE_OK) {
+		if (results.curl_result != CURLE_OK &&
+		    results.http_code != 416) {
 			struct url_info url;
 			char *nurl = url_normalize(preq->url, &url);
 			if (!nurl || !git_env_bool("GIT_TRACE_REDACT", 1)) {
diff --git a/http-push.c b/http-push.c
index 60f6f8f054..ef8abe3908 100644
--- a/http-push.c
+++ b/http-push.c
@@ -595,7 +595,8 @@ static void finish_request(struct transfer_request *request)
 
 	} else if (request->state == RUN_FETCH_PACKED) {
 		int fail = 1;
-		if (request->curl_result != CURLE_OK) {
+		if (request->curl_result != CURLE_OK &&
+		    request->http_code != 416) {
 			fprintf(stderr, "Unable to get pack file %s\n%s",
 				request->url, curl_errorstr);
 		} else {
diff --git a/http-walker.c b/http-walker.c
index b58a3b2a92..abafca84d6 100644
--- a/http-walker.c
+++ b/http-walker.c
@@ -451,7 +451,8 @@ static int http_fetch_pack(struct walker *walker, struct alt_base *repo,
 
 	if (start_active_slot(preq->slot)) {
 		run_active_slot(preq->slot);
-		if (results.curl_result != CURLE_OK) {
+		if (results.curl_result != CURLE_OK &&
+		    results.http_code != 416) {
 			error("Unable to get pack file %s\n%s", preq->url,
 			      curl_errorstr);
 			goto abort;
diff --git a/t/t5550-http-fetch-dumb.sh b/t/t5550-http-fetch-dumb.sh
index f00eeae48f..698bbb3160 100755
--- a/t/t5550-http-fetch-dumb.sh
+++ b/t/t5550-http-fetch-dumb.sh
@@ -293,6 +293,25 @@ test_expect_success 'http-fetch --packfile' '
 	git -C packfileclient cat-file -e "$HASH"
 '
 
+test_expect_success 'http-fetch --packfile accepts an already complete partial' '
+	git init packfileclient-complete &&
+	p=$(cd "$HTTPD_DOCUMENT_ROOT_PATH"/repo_pack.git &&
+		ls objects/pack/pack-*.pack) &&
+	packhash=$(basename "$p" .pack) &&
+	packhash=${packhash#pack-} &&
+	tmpfile="packfileclient-complete/.git/objects/pack/pack-$packhash.pack.temp" &&
+	cp "$HTTPD_DOCUMENT_ROOT_PATH/repo_pack.git/$p" "$tmpfile" &&
+	chmod u+w "$tmpfile" &&
+	GIT_TRACE_CURL="$TRASH_DIRECTORY/complete.trace" \
+	git -C packfileclient-complete http-fetch --packfile="$packhash" \
+		--index-pack-arg=index-pack \
+		--index-pack-arg=--stdin --index-pack-arg=--keep \
+		"$HTTPD_URL/dumb/repo_pack.git/$p" >out &&
+	test_grep "416 Requested Range Not Satisfiable" complete.trace &&
+	test_path_is_missing "$tmpfile" &&
+	git -C packfileclient-complete cat-file -e "$HASH"
+'
+
 test_expect_success 'fetch notices corrupt pack' '
 	cp -R "$HTTPD_DOCUMENT_ROOT_PATH"/repo_pack.git "$HTTPD_DOCUMENT_ROOT_PATH"/repo_bad1.git &&
 	(cd "$HTTPD_DOCUMENT_ROOT_PATH"/repo_bad1.git &&
-- 
2.55.0.openai.131.g83a728de1eb6