[PATCH 1/2] http: advertise capabilities when cloning empty repos
- From
brian m. carlson <sandals@crustytoothpaste.net>
- Date
- Apr 26, 2023, 20:53 UTC
- Message-ID
- <20230426205324.326501-2-sandals@crustytoothpaste.net>
- In-Reply-To
- <20230426205324.326501-1-sandals@crustytoothpaste.net>
From: "brian m. carlson" <bk2204@github.com>
When cloning an empty repository, the HTTP protocol version 0 currently offers nothing but the header and flush packets for the /info/refs endpoint. This means that no capabilities are provided, so the client side doesn't know what capabilities are present.
However, this does pose a problem when working with SHA-256 repositories, since we use the capabilities to know the remote side's object format (hash algorithm). It used to be possible to set the correct algorithm with `GIT_DEFAULT_HASH` (which is what the Git LFS testsuite did), but this no longer works as of 8b214c2e9d ("clone: propagate object-format when cloning from void", 2023-04-05), since there we always read the hash algorithm from the remote. If there is no hash algorithm provided, we default to SHA-1 for backwards compatibility.
Fortunately, the push version of the protocol already indicates a clue for how to solve this. When the /info/refs endpoint is accessed for a push and the remote is empty, we include a dummy "capabilities^{}" ref pointing to the all-zeros object ID. The protocol documentation already indicates this should _always_ be sent, even for fetches and clones, so let's just do that, which means we'll properly announce the hash algorithm as part of the capabilities. This just works with the existing code because we share the same ref code for fetches and clones, and libgit2 does as well.
Signed-off-by: brian m. carlson <bk2204@github.com> --- t/t5551-http-fetch-smart.sh | 27 +++++++++++++++++++++++++++ t/t5700-protocol-v1.sh | 21 +++++++++++++++++++-- upload-pack.c | 4 ++++ 3 files changed, 50 insertions(+), 2 deletions(-)
diff --git a/t/t5551-http-fetch-smart.sh b/t/t5551-http-fetch-smart.sh index 0908534f25..21b7767cbd 100755 --- a/t/t5551-http-fetch-smart.sh +++ b/t/t5551-http-fetch-smart.sh @@ -611,6 +611,33 @@ test_expect_success 'client falls back from v2 to v0 to match server' ' grep symref=HEAD:refs/heads/ trace ' +test_expect_success 'create empty http-accessible SHA-256 repository' ' + mkdir "$HTTPD_DOCUMENT_ROOT_PATH/sha256.git" && + (cd "$HTTPD_DOCUMENT_ROOT_PATH/sha256.git" && + git --bare init --object-format=sha256 + ) +' + +test_expect_success 'clone empty SHA-256 repository with protocol v2' ' + rm -fr sha256 && + echo sha256 >expected && + git -c protocol.version=2 clone "$HTTPD_URL/smart/sha256.git" && + git -C sha256 rev-parse --show-object-format >actual && + test_cmp actual expected && + git ls-remote "$HTTPD_URL/smart/sha256.git" >actual && + test_must_be_empty actual +' + +test_expect_success 'clone empty SHA-256 repository with protocol v0' ' + rm -fr sha256 && + echo sha256 >expected && + GIT_TRACE=1 GIT_TRACE_PACKET=1 git -c protocol.version=0 clone "$HTTPD_URL/smart/sha256.git" && + git -C sha256 rev-parse --show-object-format >actual && + test_cmp actual expected && + git ls-remote "$HTTPD_URL/smart/sha256.git" >actual && + test_must_be_empty actual +' + test_expect_success 'passing hostname resolution information works' ' BOGUS_HOST=gitbogusexamplehost.invalid && BOGUS_HTTPD_URL=$HTTPD_PROTO://$BOGUS_HOST:$LIB_HTTPD_PORT && diff --git a/t/t5700-protocol-v1.sh b/t/t5700-protocol-v1.sh index 6c8d4c6cf1..3cd9db9012 100755 --- a/t/t5700-protocol-v1.sh +++ b/t/t5700-protocol-v1.sh @@ -249,10 +249,12 @@ test_expect_success 'push with ssh:// using protocol v1' ' . "$TEST_DIRECTORY"/lib-httpd.sh start_httpd -test_expect_success 'create repo to be served by http:// transport' ' +test_expect_success 'create repos to be served by http:// transport' ' git init "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" && git -C "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" config http.receivepack true && - test_commit -C "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" one + test_commit -C "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" one && + git init --object-format=sha256 "$HTTPD_DOCUMENT_ROOT_PATH/sha256" && + git -C "$HTTPD_DOCUMENT_ROOT_PATH/sha256" config http.receivepack true ' test_expect_success 'clone with http:// using protocol v1' ' @@ -269,6 +271,21 @@ test_expect_success 'clone with http:// using protocol v1' ' grep "git< version 1" log ' +test_expect_success 'clone with http:// using protocol v1 with empty SHA-256 repo' ' + GIT_TRACE_PACKET=1 GIT_TRACE_CURL=1 git -c protocol.version=1 \ + clone "$HTTPD_URL/smart/sha256" sha256 2>log && + + cat log && + echo sha256 >expect && + git -C sha256 rev-parse --show-object-format >actual && + test_cmp expect actual && + + # Client requested to use protocol v1 + grep "Git-Protocol: version=1" log && + # Server responded using protocol v1 + grep "git< version 1" log +' + test_expect_success 'fetch with http:// using protocol v1' ' test_commit -C "$HTTPD_DOCUMENT_ROOT_PATH/http_parent" two && diff --git a/upload-pack.c b/upload-pack.c index 08633dc121..5ef9b162b6 100644 --- a/upload-pack.c +++ b/upload-pack.c @@ -120,6 +120,7 @@ struct upload_pack_data { unsigned allow_ref_in_want : 1; /* v2 only */ unsigned allow_sideband_all : 1; /* v2 only */ unsigned advertise_sid : 1; + unsigned sent_capabilities : 1; }; static void upload_pack_data_init(struct upload_pack_data *data) @@ -1240,6 +1241,7 @@ static int send_ref(const char *refname, const struct object_id *oid, git_user_agent_sanitized()); strbuf_release(&symref_info); strbuf_release(&session_id); + data->sent_capabilities = 1; } else { packet_fwrite_fmt(stdout, "%s %s\n", oid_to_hex(oid), refname_nons); } @@ -1379,6 +1381,8 @@ void upload_pack(const int advertise_refs, const int stateless_rpc, data.no_done = 1; head_ref_namespaced(send_ref, &data); for_each_namespaced_ref(send_ref, &data); + if (!data.sent_capabilities && advertise_refs) + send_ref("capabilities^{}", null_oid(), 0, &data); /* * fflush stdout before calling advertise_shallow_grafts because send_ref * uses stdio.