Merge branch 'jt/receive-pack-skip-connectivity-check'

"git receive-pack" optionally learns not to care about connectivity
check, which can be useful when the repository arranges to ensure
connectivity by some other means.

* jt/receive-pack-skip-connectivity-check:
  builtin/receive-pack: add option to skip connectivity check
  t5410: test receive-pack connectivity check

5 files changed, 122 insertions, 63 deletions

diff --git a/Documentation/git-receive-pack.adoc b/Documentation/git-receive-pack.adoc
index 20aca92073..0956086d61 100644
--- a/Documentation/git-receive-pack.adoc
+++ b/Documentation/git-receive-pack.adoc
@@ -46,6 +46,18 @@ OPTIONS
 	`$GIT_URL/info/refs?service=git-receive-pack` requests. See
 	`--http-backend-info-refs` in linkgit:git-upload-pack[1].
 
+--skip-connectivity-check::
+	Bypasses the connectivity checks that validate the existence of all
+	objects in the transitive closure of reachable objects. This option is
+	intended for server operators that want to implement their own object
+	connectivity validation outside of Git. This is useful in such cases
+	where the server-side knows additional information about how Git is
+	being used and thus can rely on certain guarantees to more efficiently
+	compute object connectivity that Git itself cannot make. Usage of this
+	option without a reliable external mechanism to ensure full reachable
+	object connectivity risks corrupting the repository and should not be
+	used in the general case.
+
 PRE-RECEIVE HOOK
 ----------------
 Before any ref is updated, if $GIT_DIR/hooks/pre-receive file exists
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index c92e57ba18..a317d6c278 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -81,6 +81,7 @@ static int prefer_ofs_delta = 1;
 static int auto_update_server_info;
 static int auto_gc = 1;
 static int reject_thin;
+static int skip_connectivity_check;
 static int stateless_rpc;
 static const char *service_dir;
 static const char *head_name;
@@ -1938,27 +1939,29 @@ static void execute_commands(struct command *commands,
 		return;
 	}
 
-	if (use_sideband) {
-		memset(&muxer, 0, sizeof(muxer));
-		muxer.proc = copy_to_sideband;
-		muxer.in = -1;
-		if (!start_async(&muxer))
-			err_fd = muxer.in;
-		/* ...else, continue without relaying sideband */
-	}
+	if (!skip_connectivity_check) {
+		if (use_sideband) {
+			memset(&muxer, 0, sizeof(muxer));
+			muxer.proc = copy_to_sideband;
+			muxer.in = -1;
+			if (!start_async(&muxer))
+				err_fd = muxer.in;
+			/* ...else, continue without relaying sideband */
+		}
 
-	data.cmds = commands;
-	data.si = si;
-	opt.err_fd = err_fd;
-	opt.progress = err_fd && !quiet;
-	opt.env = tmp_objdir_env(tmp_objdir);
-	opt.exclude_hidden_refs_section = "receive";
+		data.cmds = commands;
+		data.si = si;
+		opt.err_fd = err_fd;
+		opt.progress = err_fd && !quiet;
+		opt.env = tmp_objdir_env(tmp_objdir);
+		opt.exclude_hidden_refs_section = "receive";
 
-	if (check_connected(iterate_receive_command_list, &data, &opt))
-		set_connectivity_errors(commands, si);
+		if (check_connected(iterate_receive_command_list, &data, &opt))
+			set_connectivity_errors(commands, si);
 
-	if (use_sideband)
-		finish_async(&muxer);
+		if (use_sideband)
+			finish_async(&muxer);
+	}
 
 	reject_updates_to_hidden(commands);
 
@@ -2519,6 +2522,7 @@ int cmd_receive_pack(int argc,
 
 	struct option options[] = {
 		OPT__QUIET(&quiet, N_("quiet")),
+		OPT_HIDDEN_BOOL(0, "skip-connectivity-check", &skip_connectivity_check, NULL),
 		OPT_HIDDEN_BOOL(0, "stateless-rpc", &stateless_rpc, NULL),
 		OPT_HIDDEN_BOOL(0, "http-backend-info-refs", &advertise_refs, NULL),
 		OPT_ALIAS(0, "advertise-refs", "http-backend-info-refs"),
diff --git a/t/meson.build b/t/meson.build
index fcfc1c2c2b..d052fc3e23 100644
--- a/t/meson.build
+++ b/t/meson.build
@@ -629,7 +629,7 @@ integration_tests = [
   't5407-post-rewrite-hook.sh',
   't5408-send-pack-stdin.sh',
   't5409-colorize-remote-messages.sh',
-  't5410-receive-pack-alternates.sh',
+  't5410-receive-pack.sh',
   't5411-proc-receive-hook.sh',
   't5500-fetch-pack.sh',
   't5501-fetch-push-alternates.sh',
diff --git a/t/t5410-receive-pack-alternates.sh b/t/t5410-receive-pack-alternates.sh
deleted file mode 100755
index 4e82fd102e..0000000000
--- a/t/t5410-receive-pack-alternates.sh
+++ /dev/null
@@ -1,44 +0,0 @@
-#!/bin/sh
-
-test_description='git receive-pack with alternate ref filtering'
-
-GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
-export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
-
-. ./test-lib.sh
-
-test_expect_success 'setup' '
-	test_commit base &&
-	git clone -s --bare . fork &&
-	git checkout -b public/branch main &&
-	test_commit public &&
-	git checkout -b private/branch main &&
-	test_commit private
-'
-
-extract_haves () {
-	depacketize | sed -n 's/^\([^ ][^ ]*\) \.have/\1/p'
-}
-
-test_expect_success 'with core.alternateRefsCommand' '
-	write_script fork/alternate-refs <<-\EOF &&
-		git --git-dir="$1" for-each-ref \
-			--format="%(objectname)" \
-			refs/heads/public/
-	EOF
-	test_config -C fork core.alternateRefsCommand ./alternate-refs &&
-	git rev-parse public/branch >expect &&
-	printf "0000" | git receive-pack fork >actual &&
-	extract_haves <actual >actual.haves &&
-	test_cmp expect actual.haves
-'
-
-test_expect_success 'with core.alternateRefsPrefixes' '
-	test_config -C fork core.alternateRefsPrefixes "refs/heads/private" &&
-	git rev-parse private/branch >expect &&
-	printf "0000" | git receive-pack fork >actual &&
-	extract_haves <actual >actual.haves &&
-	test_cmp expect actual.haves
-'
-
-test_done
diff --git a/t/t5410-receive-pack.sh b/t/t5410-receive-pack.sh
new file mode 100755
index 0000000000..f76a22943e
--- /dev/null
+++ b/t/t5410-receive-pack.sh
@@ -0,0 +1,87 @@
+#!/bin/sh
+
+test_description='git receive-pack'
+
+GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
+export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	test_commit base &&
+	git clone -s --bare . fork &&
+	git checkout -b public/branch main &&
+	test_commit public &&
+	git checkout -b private/branch main &&
+	test_commit private
+'
+
+extract_haves () {
+	depacketize | sed -n 's/^\([^ ][^ ]*\) \.have/\1/p'
+}
+
+test_expect_success 'with core.alternateRefsCommand' '
+	write_script fork/alternate-refs <<-\EOF &&
+		git --git-dir="$1" for-each-ref \
+			--format="%(objectname)" \
+			refs/heads/public/
+	EOF
+	test_config -C fork core.alternateRefsCommand ./alternate-refs &&
+	git rev-parse public/branch >expect &&
+	printf "0000" | git receive-pack fork >actual &&
+	extract_haves <actual >actual.haves &&
+	test_cmp expect actual.haves
+'
+
+test_expect_success 'with core.alternateRefsPrefixes' '
+	test_config -C fork core.alternateRefsPrefixes "refs/heads/private" &&
+	git rev-parse private/branch >expect &&
+	printf "0000" | git receive-pack fork >actual &&
+	extract_haves <actual >actual.haves &&
+	test_cmp expect actual.haves
+'
+
+test_expect_success 'receive-pack missing objects fails connectivity check' '
+	test_when_finished rm -rf repo remote.git setup.git &&
+
+	git init repo &&
+	git -C repo commit --allow-empty -m 1 &&
+	git clone --bare repo setup.git &&
+	git -C repo commit --allow-empty -m 2 &&
+
+	# Capture git-send-pack(1) output sent to git-receive-pack(1).
+	git -C repo send-pack ../setup.git --all \
+		--receive-pack="tee ${SQ}$(pwd)/out${SQ} | git-receive-pack" &&
+
+	# Replay captured git-send-pack(1) output on new empty repository.
+	git init --bare remote.git &&
+	git receive-pack remote.git <out >actual 2>err &&
+
+	test_grep "missing necessary objects" actual &&
+	test_grep "fatal: Failed to traverse parents" err &&
+	test_must_fail git -C remote.git cat-file -e $(git -C repo rev-parse HEAD)
+'
+
+test_expect_success 'receive-pack missing objects bypasses connectivity check' '
+	test_when_finished rm -rf repo remote.git setup.git &&
+
+	git init repo &&
+	git -C repo commit --allow-empty -m 1 &&
+	git clone --bare repo setup.git &&
+	git -C repo commit --allow-empty -m 2 &&
+
+	# Capture git-send-pack(1) output sent to git-receive-pack(1).
+	git -C repo send-pack ../setup.git --all \
+		--receive-pack="tee ${SQ}$(pwd)/out${SQ} | git-receive-pack" &&
+
+	# Replay captured git-send-pack(1) output on new empty repository.
+	git init --bare remote.git &&
+	git receive-pack --skip-connectivity-check remote.git <out >actual 2>err &&
+
+	test_grep ! "missing necessary objects" actual &&
+	test_must_be_empty err &&
+	git -C remote.git cat-file -e $(git -C repo rev-parse HEAD) &&
+	test_must_fail git -C remote.git rev-list $(git -C repo rev-parse HEAD)
+'
+
+test_done