From 4202813b300cc708d40b2a307405360e30b30a6a Mon Sep 17 00:00:00 2001 From: Karthik Nayak Date: Wed, 26 Aug 2026 12:19:37 +0200 Subject: [PATCH 1/3] doc: add proc-receive hook info in 'git-receive-pack.adoc' The 'Documentation/git-receive-pack.adoc' contains documentation about hooks which lie in the lifecycle of 'git-receive-pack(1)'. Unfortunately it is missing information about the 'proc-receive' hook. Add it. Signed-off-by: Karthik Nayak Signed-off-by: Junio C Hamano --- Documentation/git-receive-pack.adoc | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/Documentation/git-receive-pack.adoc b/Documentation/git-receive-pack.adoc index 0956086d61..4349487e6a 100644 --- a/Documentation/git-receive-pack.adoc +++ b/Documentation/git-receive-pack.adoc @@ -236,6 +236,12 @@ if the repository is packed and is served via a dumb transport. exec git update-server-info ---- +PROC-RECEIVE HOOK +----------------- +This hook is invoked by 'git-receive-pack' when it processes push +requests. It handles refs whose names match the patterns defined by +`receive.procReceiveRefs` and executes the actual ref updates. See +linkgit:githooks[5] for the full protocol description. QUARANTINE ENVIRONMENT ---------------------- From 063bb0a9870e73843d4d5c9ec75e799d37c44ca5 Mon Sep 17 00:00:00 2001 From: Karthik Nayak Date: Wed, 26 Aug 2026 12:19:38 +0200 Subject: [PATCH 2/3] receive-pack: move message generation to separate function Post the reference transaction, both `report()` and `report_v2()` generate the message to be sent to the client. In v2, we also add reports for each reference if available. Since they share common code, move them to a common function. This will also help the following commit, where we will need to regenerate the message during hook failure. Signed-off-by: Karthik Nayak Signed-off-by: Junio C Hamano --- builtin/receive-pack.c | 94 ++++++++++++++++++++++-------------------- 1 file changed, 49 insertions(+), 45 deletions(-) diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c index 86933d8d7e..70a686c142 100644 --- a/builtin/receive-pack.c +++ b/builtin/receive-pack.c @@ -2530,22 +2530,58 @@ static void update_shallow_info(struct command *commands, free(ref_status); } -static void report(struct command *commands, const char *unpack_status) +/* + * Generate the response to be sent to the client invoking 'git-receive-pack(1)'. + * For v2 protocol, set `add_reports` to true, which will also add additional + * report per reference update. + */ +static void generate_response(struct strbuf *buf, struct command *commands, + const char *unpack_status, bool add_reports) { struct command *cmd; + + packet_buf_write(buf, "unpack %s\n", + unpack_status ? unpack_status : "ok"); + + for (cmd = commands; cmd; cmd = cmd->next) { + struct ref_push_report *report; + int count = 0; + + if (cmd->error_string) + packet_buf_write(buf, "ng %s %s\n", + cmd->ref_name, cmd->error_string); + else + packet_buf_write(buf, "ok %s\n", cmd->ref_name); + + if (!add_reports || cmd->error_string) + continue; + + for (report = cmd->report; report; report = report->next) { + if (count++ > 0) + packet_buf_write(buf, "ok %s\n", + cmd->ref_name); + if (report->ref_name) + packet_buf_write(buf, "option refname %s\n", + report->ref_name); + if (report->old_oid) + packet_buf_write(buf, "option old-oid %s\n", + oid_to_hex(report->old_oid)); + if (report->new_oid) + packet_buf_write(buf, "option new-oid %s\n", + oid_to_hex(report->new_oid)); + if (report->forced_update) + packet_buf_write(buf, "option forced-update\n"); + } + } + + packet_buf_flush(buf); +} + +static void report(struct command *commands, const char *unpack_status) +{ struct strbuf buf = STRBUF_INIT; - packet_buf_write(&buf, "unpack %s\n", - unpack_status ? unpack_status : "ok"); - for (cmd = commands; cmd; cmd = cmd->next) { - if (!cmd->error_string) - packet_buf_write(&buf, "ok %s\n", - cmd->ref_name); - else - packet_buf_write(&buf, "ng %s %s\n", - cmd->ref_name, cmd->error_string); - } - packet_buf_flush(&buf); + generate_response(&buf, commands, unpack_status, false); if (use_sideband) send_sideband(1, 1, buf.buf, buf.len, use_sideband); @@ -2556,41 +2592,9 @@ static void report(struct command *commands, const char *unpack_status) static void report_v2(struct command *commands, const char *unpack_status) { - struct command *cmd; struct strbuf buf = STRBUF_INIT; - struct ref_push_report *report; - packet_buf_write(&buf, "unpack %s\n", - unpack_status ? unpack_status : "ok"); - for (cmd = commands; cmd; cmd = cmd->next) { - int count = 0; - - if (cmd->error_string) { - packet_buf_write(&buf, "ng %s %s\n", - cmd->ref_name, - cmd->error_string); - continue; - } - packet_buf_write(&buf, "ok %s\n", - cmd->ref_name); - for (report = cmd->report; report; report = report->next) { - if (count++ > 0) - packet_buf_write(&buf, "ok %s\n", - cmd->ref_name); - if (report->ref_name) - packet_buf_write(&buf, "option refname %s\n", - report->ref_name); - if (report->old_oid) - packet_buf_write(&buf, "option old-oid %s\n", - oid_to_hex(report->old_oid)); - if (report->new_oid) - packet_buf_write(&buf, "option new-oid %s\n", - oid_to_hex(report->new_oid)); - if (report->forced_update) - packet_buf_write(&buf, "option forced-update\n"); - } - } - packet_buf_flush(&buf); + generate_response(&buf, commands, unpack_status, true); if (use_sideband) send_sideband(1, 1, buf.buf, buf.len, use_sideband); From 16861b5365da1af369cd60c6fdc8874fbfa0188b Mon Sep 17 00:00:00 2001 From: Karthik Nayak Date: Wed, 26 Aug 2026 12:19:39 +0200 Subject: [PATCH 3/3] hook: introduce the receive-report hook When running 'git-receive-pack(1)', there is no way for the server to intercept and modify the status report before it is sent back to the client. Servers with custom logic may need to transform or gate the report based on the outcome of external logic post reference updates. This is specially needed for our usecase at GitLab where we have custom MVCC logic on top of Git which creates a new version for each push operation. The new version is only committed when certain external operations post reference transaction succeed. So reporting the correct message based on the outcome of these operations is important. We cannot use any of the existing hooks as: - The pre-receive hook runs too early, as we haven't updated references at that point yet and we need to have the full view of all resulting updates (both objects and references). - The update hook is too inefficient as it runs once per reference, and we cannot trivially determine the last update. - The reference-transaction hook cannot be used by us because we care about the phase where it was committed already. And while the hook fires in that phase, it does not allow the caller to modify the result in any capacity. - The post-receive and post-update hooks cannot be used as they run too late, at the point where we have already reported success to the client. Introduce a new 'receive-report' hook. The hook receives the complete pkt-line encoded status report on standard input, after all ref updates have been applied to the repository by execute_commands() but before the report is sent to the client. See linkgit:gitprotocol-pack[5] details on the protocol structure. The hook's stdout fully replaces the report sent to the client. receive-pack fully buffers the hook's stdout before acting on the exit status, so the exit code is known before the client receives anything. This gives two distinct behaviors depending on exit status: - Exit 0: the hook's stdout is used as the report. The hook can rewrite 'ok' lines to 'ng' lines to signal per-ref rejection to the client while receive-pack itself exits cleanly. The client marks rejected refs as '[remote rejected]' and exits with a non-zero status if any ref is 'ng'. - Non-zero exit: the hook's stdout is discarded, receive-pack modifies all references to be rejected with a 'receive-report hook failed' error. In both cases, any output the hook writes to standard error is forwarded to the client over the sideband channel and appears as 'remote:' lines on the client terminal. Writing to stderr alone does not affect the push outcome. Note that in either failure mode, ref updates already applied by execute_commands() are not rolled back. The hook can cause the client to perceive the push as failed, but cannot undo server-side changes. This hook does not use the config-based hook infrastructure, which supports running multiple scripts per hook event. This hook is a bidirectional filter: it receives the report on stdin and writes a modified version to stdout. Running multiple such scripts sequentially would require piping the output of one into the input of the next, which the current hook infrastructure does not support. A single-script design is therefore a natural fit, and is consistent with how 'proc-receive' is structured for the same reason. Helped-by: Patrick Steinhardt Signed-off-by: Karthik Nayak Signed-off-by: Junio C Hamano --- Documentation/git-receive-pack.adoc | 9 ++ Documentation/githooks.adoc | 43 ++++++ builtin/receive-pack.c | 61 ++++++++- t/meson.build | 1 + t/t5412-receive-report-hook.sh | 200 ++++++++++++++++++++++++++++ 5 files changed, 310 insertions(+), 4 deletions(-) create mode 100755 t/t5412-receive-report-hook.sh diff --git a/Documentation/git-receive-pack.adoc b/Documentation/git-receive-pack.adoc index 4349487e6a..f2d52b7df2 100644 --- a/Documentation/git-receive-pack.adoc +++ b/Documentation/git-receive-pack.adoc @@ -243,6 +243,15 @@ requests. It handles refs whose names match the patterns defined by `receive.procReceiveRefs` and executes the actual ref updates. See linkgit:githooks[5] for the full protocol description. +RECEIVE-REPORT HOOK +------------------- +This hook is invoked by 'git-receive-pack' after all the ref updates +have been applied but before the report is sent to the client. The hook +receives the complete report in pkt-line format on stdin and its stdout +replaces the report sent to the client. Allowing the hook to rewrite +the outcomes or abort the push completely. See linkgit:githooks[5] for +the full protocol description. + QUARANTINE ENVIRONMENT ---------------------- diff --git a/Documentation/githooks.adoc b/Documentation/githooks.adoc index ed045940d1..e83ebde667 100644 --- a/Documentation/githooks.adoc +++ b/Documentation/githooks.adoc @@ -527,6 +527,49 @@ The exit status of the hook is ignored for any state except for the status will cause the transaction to be aborted. The hook will not be called with "aborted" state in that case. +receive-report +~~~~~~~~~~~~~~ + +This hook is invoked by linkgit:git-receive-pack[1] when it reacts to +`git push` and updates references in its repository. It executes on +the repository once after all refs have been updated and after all +accepted ref changes are applied to the repository, but before the +pkt-line encoded status report is sent back to the client. + +The hook receives the complete pkt-line encoded status report on +standard input, see linkgit:gitprotocol-pack[5] for details on the +structure. The hook's standard output entirely replaces the report +that is sent to the client. The hook must write a valid pkt-line +encoded report in the same format it received. The hook's stdout is +fully buffered by `receive-pack` before any data is sent to the client, +so the hook's exit status is known before the client receives anything. + +There are two distinct ways the hook can affect the push outcome: + +* To reject individual ref updates while keeping `receive-pack` alive, + rewrite the corresponding `ok ` lines to + `ng ` lines in the output and exit with status 0. + The client will then mark those specific refs as rejected while + treating any `ok` refs as successful. The push as a whole is + considered failed if any ref is `ng`, and `git push` will exit with + a non-zero status on the client side. + +* To abort the entire push unconditionally, exit with a non-zero + status. In this case the hook's stdout is discarded, `receive-pack` + modifies all references to be rejected with a 'receive-report hook + failed' error. + +Any output written to standard error is forwarded to the client over +the sideband channel and will appear as `remote:` lines on clients +using 'git-push(1)', regardless of the hook's exit status. Writing to +standard error alone does not affect the push outcome. + +Note that by the time this hook runs, all ref updates have already been +applied to the repository. Neither a non-zero exit nor rewriting refs +to `ng` rolls back any ref changes that were already committed +server-side. The hook can cause the client to perceive the push as +failed, but cannot undo the server-side updates. + push-to-checkout ~~~~~~~~~~~~~~~~ diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c index 70a686c142..1358285589 100644 --- a/builtin/receive-pack.c +++ b/builtin/receive-pack.c @@ -1004,6 +1004,41 @@ static int run_update_hook(struct command *cmd) return code; } +static int run_receive_report_hook(struct strbuf *report) +{ + struct child_process proc = CHILD_PROCESS_INIT; + struct async sideband_async; + int sideband_async_started = 0; + int saved_stderr = -1; + struct strbuf out = STRBUF_INIT; + const char *hook_path; + int ret; + + hook_path = find_hook(the_repository, "receive-report"); + if (!hook_path) + return 0; + + strvec_push(&proc.args, hook_path); + proc.trace2_hook_name = "receive-report"; + + prepare_sideband_async(&sideband_async, &saved_stderr, + &sideband_async_started); + + sigchain_push(SIGPIPE, SIG_IGN); + ret = pipe_command(&proc, report->buf, report->len, &out, + report->len, NULL, 0); + sigchain_pop(SIGPIPE); + + finish_sideband_async(&sideband_async, saved_stderr, + sideband_async_started); + + if (!ret) + strbuf_swap(&out, report); + + strbuf_release(&out); + return ret; +} + static struct command *find_command_by_refname(struct command *list, const char *refname) { @@ -2534,9 +2569,12 @@ static void update_shallow_info(struct command *commands, * Generate the response to be sent to the client invoking 'git-receive-pack(1)'. * For v2 protocol, set `add_reports` to true, which will also add additional * report per reference update. + * If `ref_error` is set, then all references will be rejected with the given + * error message. */ static void generate_response(struct strbuf *buf, struct command *commands, - const char *unpack_status, bool add_reports) + const char *unpack_status, bool add_reports, + const char *ref_error) { struct command *cmd; @@ -2550,10 +2588,13 @@ static void generate_response(struct strbuf *buf, struct command *commands, if (cmd->error_string) packet_buf_write(buf, "ng %s %s\n", cmd->ref_name, cmd->error_string); + else if (ref_error) + packet_buf_write(buf, "ng %s %s\n", + cmd->ref_name, ref_error); else packet_buf_write(buf, "ok %s\n", cmd->ref_name); - if (!add_reports || cmd->error_string) + if (!add_reports || cmd->error_string || ref_error) continue; for (report = cmd->report; report; report = report->next) { @@ -2581,7 +2622,13 @@ static void report(struct command *commands, const char *unpack_status) { struct strbuf buf = STRBUF_INIT; - generate_response(&buf, commands, unpack_status, false); + generate_response(&buf, commands, unpack_status, false, NULL); + + if (run_receive_report_hook(&buf)) { + strbuf_reset(&buf); + generate_response(&buf, commands, unpack_status, false, + "receive-report hook failed"); + } if (use_sideband) send_sideband(1, 1, buf.buf, buf.len, use_sideband); @@ -2594,7 +2641,13 @@ static void report_v2(struct command *commands, const char *unpack_status) { struct strbuf buf = STRBUF_INIT; - generate_response(&buf, commands, unpack_status, true); + generate_response(&buf, commands, unpack_status, true, NULL); + + if (run_receive_report_hook(&buf)) { + strbuf_reset(&buf); + generate_response(&buf, commands, unpack_status, true, + "receive-report hook failed"); + } if (use_sideband) send_sideband(1, 1, buf.buf, buf.len, use_sideband); diff --git a/t/meson.build b/t/meson.build index 2133c840da..b698c6735b 100644 --- a/t/meson.build +++ b/t/meson.build @@ -652,6 +652,7 @@ integration_tests = [ 't5409-colorize-remote-messages.sh', 't5410-receive-pack.sh', 't5411-proc-receive-hook.sh', + 't5412-receive-report-hook.sh', 't5500-fetch-pack.sh', 't5501-fetch-push-alternates.sh', 't5502-quickfetch.sh', diff --git a/t/t5412-receive-report-hook.sh b/t/t5412-receive-report-hook.sh new file mode 100755 index 0000000000..1ba188e964 --- /dev/null +++ b/t/t5412-receive-report-hook.sh @@ -0,0 +1,200 @@ +#!/bin/sh + +test_description='test receive-report hook' + +GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main +export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME + +. ./test-lib.sh + +. "$TEST_DIRECTORY"/t5411/common-functions.sh + +URL_PREFIX="\.\." + +test_expect_success "setup workbench" ' + git init workbench && + create_commits_in workbench A B +' + +test_expect_success "no report hook, push succeeds" ' + test_when_finished "rm -rf upstream" && + test_when_finished "git -C workbench remote remove origin" && + git init --bare upstream && + + git -C workbench remote add origin ../upstream && + git -C workbench push origin $A:refs/heads/main && + git -C workbench push origin $B:refs/heads/main >out 2>&1 && + + make_user_friendly_and_stable_output actual && + cat >expect <<-\EOF && + To ../upstream + .. -> main + EOF + test_cmp expect actual +' + +test_expect_success "passthrough does not alter report" ' + test_when_finished "rm -rf upstream" && + test_when_finished "git -C workbench remote remove origin" && + git init --bare upstream && + + test_hook -C upstream --setup receive-report <<-\EOF && + cat + EOF + + git -C workbench remote add origin ../upstream && + git -C workbench push origin $A:refs/heads/main && + git -C workbench push origin $B:refs/heads/main >out 2>&1 && + + make_user_friendly_and_stable_output actual && + cat >expect <<-\EOF && + To ../upstream + .. -> main + EOF + test_cmp expect actual +' + +test_expect_success "non-zero exit reports as hook failed" ' + test_when_finished "rm -rf upstream" && + test_when_finished "git -C workbench remote remove origin" && + + git init --bare upstream && + git -C workbench remote add origin ../upstream && + git -C workbench push origin $A:refs/heads/main && + + test_hook -C upstream --setup receive-report <<-\EOF && + exit 1 + EOF + + test_must_fail git -C workbench push origin $B:refs/heads/main >out 2>&1 && + make_user_friendly_and_stable_output actual && + cat >expect <<-\EOF && + To ../upstream + ! [remote rejected] -> main (receive-report hook failed) + EOF + test_cmp expect actual +' + +test_expect_success "hook is invoked and receives report on stdin" ' + test_when_finished "rm -rf upstream" && + test_when_finished "git -C workbench remote remove origin" && + + git init --bare upstream && + test_hook -C upstream --setup receive-report <<-EOF && + tee raw + EOF + + git -C workbench remote add origin ../upstream && + git -C workbench push origin $A:refs/heads/main && + git -C workbench push origin $B:refs/heads/main >out 2>&1 && + + make_user_friendly_and_stable_output actual && + cat >expect <<-EOF && + To ../upstream + .. -> main + EOF + test_cmp expect actual && + + test-tool pkt-line unpack actual-report && + cat >expect-report <<-EOF && + unpack ok + ok refs/heads/main + 0000 + EOF + test_cmp expect-report actual-report +' + +test_expect_success "hook can modify the report sent to client" ' + test_when_finished "rm -rf upstream" && + test_when_finished "git -C workbench remote remove origin" && + + git init --bare upstream && + git -C workbench remote add origin ../upstream && + git -C workbench push origin $A:refs/heads/main && + + test_hook -C upstream --setup receive-report <<-\EOF && + test-tool pkt-line unpack | + sed "s/^ok /ng /" | + test-tool pkt-line pack + EOF + + test_must_fail git -C workbench push origin $B:refs/heads/main >out 2>&1 && + make_user_friendly_and_stable_output actual && + cat >expect <<-\EOF && + To ../upstream + ! [remote rejected] -> main (failed) + EOF + test_cmp expect actual +' + +test_expect_success "hook can report a custom failure message" ' + test_when_finished "rm -rf upstream" && + test_when_finished "git -C workbench remote remove origin" && + + git init --bare upstream && + git -C workbench remote add origin ../upstream && + git -C workbench push origin $A:refs/heads/main && + + test_hook -C upstream --setup receive-report <<-\EOF && + echo "push rejected: service X is down" >&2 + test-tool pkt-line unpack | + sed "s/^ok \(.*\)/ng \1 service-x-is-down/" | + test-tool pkt-line pack | + tee raw + EOF + + test_must_fail git -C workbench push origin $B:refs/heads/main >out 2>&1 && + test_grep "push rejected: service X is down" out && + + test-tool pkt-line unpack actual-report && + cat >expect-report <<-\EOF && + unpack ok + ng refs/heads/main service-x-is-down + 0000 + EOF + test_cmp expect-report actual-report +' + +test_expect_success "hook stderr with zero exit status code" ' + test_when_finished "rm -rf upstream" && + test_when_finished "git -C workbench remote remove origin" && + + git init --bare upstream && + git -C workbench remote add origin ../upstream && + git -C workbench push origin $A:refs/heads/main && + + test_hook -C upstream --setup receive-report <<-\EOF && + echo "push rejected: service X is down" >&2 + tee raw + EOF + + git -C workbench push origin $B:refs/heads/main >out 2>&1 && + test_grep "push rejected: service X is down" out && + + test-tool pkt-line unpack actual-report && + cat >expect-report <<-\EOF && + unpack ok + ok refs/heads/main + 0000 + EOF + test_cmp expect-report actual-report +' + +test_expect_success "hook stderr is relayed to client via sideband" ' + test_when_finished "rm -rf upstream" && + test_when_finished "git -C workbench remote remove origin" && + + git init --bare upstream && + git -C workbench remote add origin ../upstream && + git -C workbench push origin $A:refs/heads/main && + + test_hook -C upstream --setup receive-report <<-\EOF && + echo "hook-stderr-message" >&2 + exit 1 + EOF + + test_must_fail git -C workbench push origin $B:refs/heads/main >out 2>&1 && + test_grep "remote: hook-stderr-message" out +' + +test_done