Merge branch 'ps/ref-transaction-hook' into jch

* ps/ref-transaction-hook:
  refs: implement reference transaction hook

Documentation/githooks.txt

@@ -404,6 +404,35 @@ Both standard output and standard error output are forwarded to
 `git send-pack` on the other end, so you can simply `echo` messages
 for the user.
 
+ref-transaction
+~~~~~~~~~~~~~~~
+
+This hook is invoked by any Git command that performs reference
+updates. It executes whenever a reference transaction is prepared,
+committed or aborted and may thus get called multiple times.
+
+The hook takes exactly one argument, which is the current state the
+given reference transaction is in:
+
+    - "prepared": All reference updates have been queued to the
+      transaction and references were locked on disk.
+
+    - "committed": The reference transaction was committed and all
+      references now have their respective new value.
+
+    - "aborted": The reference transaction was aborted, no changes
+      were performed and the locks have been released.
+
+For each reference update that was added to the transaction, the hook
+receives on standard input a line of the format:
+
+  <old-value> SP <new-value> SP <ref-name> LF
+
+The exit status of the hook is ignored for any state except for the
+"prepared" state. In the "prepared" state, a non-zero exit status will
+cause the transaction to be aborted. The hook will not be called with
+"aborted" state in that case.
+
 push-to-checkout
 ~~~~~~~~~~~~~~~~
 

refs.c

@@ -9,6 +9,7 @@
 #include "iterator.h"
 #include "refs.h"
 #include "refs/refs-internal.h"
+#include "run-command.h"
 #include "object-store.h"
 #include "object.h"
 #include "tag.h"
@@ -16,6 +17,7 @@
 #include "worktree.h"
 #include "argv-array.h"
 #include "repository.h"
+#include "sigchain.h"
 
 /*
  * List of all available backends
@@ -1986,10 +1988,65 @@ int ref_update_reject_duplicates(struct string_list *refnames,
 	return 0;
 }
 
+static const char hook_not_found;
+static const char *hook;
+
+static int run_transaction_hook(struct ref_transaction *transaction,
+				const char *state)
+{
+	struct child_process proc = CHILD_PROCESS_INIT;
+	struct strbuf buf = STRBUF_INIT;
+	int ret = 0, i;
+
+	if (hook == &hook_not_found)
+		return ret;
+	if (!hook)
+		hook = find_hook("reference-transaction");
+	if (!hook) {
+		hook = &hook_not_found;
+		return ret;
+	}
+
+	argv_array_pushl(&proc.args, hook, state, NULL);
+	proc.in = -1;
+	proc.stdout_to_stderr = 1;
+	proc.trace2_hook_name = "reference-transaction";
+
+	ret = start_command(&proc);
+	if (ret)
+		return ret;
+
+	sigchain_push(SIGPIPE, SIG_IGN);
+
+	for (i = 0; i < transaction->nr; i++) {
+		struct ref_update *update = transaction->updates[i];
+
+		strbuf_reset(&buf);
+		strbuf_addf(&buf, "%s %s %s\n",
+			    oid_to_hex(&update->old_oid),
+			    oid_to_hex(&update->new_oid),
+			    update->refname);
+
+		if (write_in_full(proc.in, buf.buf, buf.len) < 0) {
+			if (errno != EPIPE)
+				ret = -1;
+			break;
+		}
+	}
+
+	close(proc.in);
+	sigchain_pop(SIGPIPE);
+	strbuf_release(&buf);
+
+	ret |= finish_command(&proc);
+	return ret;
+}
+
 int ref_transaction_prepare(struct ref_transaction *transaction,
 			    struct strbuf *err)
 {
 	struct ref_store *refs = transaction->ref_store;
+	int ret;
 
 	switch (transaction->state) {
 	case REF_TRANSACTION_OPEN:
@@ -2012,7 +2069,17 @@ int ref_transaction_prepare(struct ref_transaction *transaction,
 		return -1;
 	}
 
-	return refs->be->transaction_prepare(refs, transaction, err);
+	ret = refs->be->transaction_prepare(refs, transaction, err);
+	if (ret)
+		return ret;
+
+	ret = run_transaction_hook(transaction, "prepared");
+	if (ret) {
+		ref_transaction_abort(transaction, err);
+		die(_("ref updates aborted by hook"));
+	}
+
+	return 0;
 }
 
 int ref_transaction_abort(struct ref_transaction *transaction,
@@ -2036,6 +2103,8 @@ int ref_transaction_abort(struct ref_transaction *transaction,
 		break;
 	}
 
+	run_transaction_hook(transaction, "aborted");
+
 	ref_transaction_free(transaction);
 	return ret;
 }
@@ -2064,7 +2133,10 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 		break;
 	}
 
-	return refs->be->transaction_finish(refs, transaction, err);
+	ret = refs->be->transaction_finish(refs, transaction, err);
+	if (!ret)
+		run_transaction_hook(transaction, "committed");
+	return ret;
 }
 
 int refs_verify_refname_available(struct ref_store *refs,

t/perf/p1400-update-ref.sh

@@ -0,0 +1,32 @@
+#!/bin/sh
+
+test_description="Tests performance of update-ref"
+
+. ./perf-lib.sh
+
+test_perf_fresh_repo
+
+test_expect_success "setup" '
+	test_commit PRE &&
+	test_commit POST &&
+	printf "create refs/heads/%d PRE\n" $(test_seq 1000) >create &&
+	printf "update refs/heads/%d POST PRE\n" $(test_seq 1000) >update &&
+	printf "delete refs/heads/%d POST\n" $(test_seq 1000) >delete
+'
+
+test_perf "update-ref" '
+	for i in $(test_seq 1000)
+	do
+		git update-ref refs/heads/branch PRE &&
+		git update-ref refs/heads/branch POST PRE &&
+		git update-ref -d refs/heads/branch
+	done
+'
+
+test_perf "update-ref --stdin" '
+	git update-ref --stdin <create &&
+	git update-ref --stdin <update &&
+	git update-ref --stdin <delete
+'
+
+test_done

t/t1416-ref-transaction-hooks.sh

@@ -0,0 +1,109 @@
+#!/bin/sh
+
+test_description='reference transaction hooks'
+
+. ./test-lib.sh
+
+test_expect_success setup '
+	mkdir -p .git/hooks &&
+	test_commit PRE &&
+	test_commit POST &&
+	POST_OID=$(git rev-parse POST)
+'
+
+test_expect_success 'hook allows updating ref if successful' '
+	test_when_finished "rm .git/hooks/reference-transaction" &&
+	git reset --hard PRE &&
+	write_script .git/hooks/reference-transaction <<-\EOF &&
+		echo "$*" >>actual
+	EOF
+	cat >expect <<-EOF &&
+		prepared
+		committed
+	EOF
+	git update-ref HEAD POST &&
+	test_cmp expect actual
+'
+
+test_expect_success 'hook aborts updating ref in prepared state' '
+	test_when_finished "rm .git/hooks/reference-transaction" &&
+	git reset --hard PRE &&
+	write_script .git/hooks/reference-transaction <<-\EOF &&
+		if test "$1" = prepared
+		then
+			exit 1
+		fi
+	EOF
+	test_must_fail git update-ref HEAD POST 2>err &&
+	test_i18ngrep "ref updates aborted by hook" err
+'
+
+test_expect_success 'hook gets all queued updates in prepared state' '
+	test_when_finished "rm .git/hooks/reference-transaction actual" &&
+	git reset --hard PRE &&
+	write_script .git/hooks/reference-transaction <<-\EOF &&
+		if test "$1" = prepared
+		then
+			while read -r line
+			do
+				printf "%s\n" "$line"
+			done >actual
+		fi
+	EOF
+	cat >expect <<-EOF &&
+		$ZERO_OID $POST_OID HEAD
+		$ZERO_OID $POST_OID refs/heads/master
+	EOF
+	git update-ref HEAD POST <<-EOF &&
+		update HEAD $ZERO_OID $POST_OID
+		update refs/heads/master $ZERO_OID $POST_OID
+	EOF
+	test_cmp expect actual
+'
+
+test_expect_success 'hook gets all queued updates in committed state' '
+	test_when_finished "rm .git/hooks/reference-transaction actual" &&
+	git reset --hard PRE &&
+	write_script .git/hooks/reference-transaction <<-\EOF &&
+		if test "$1" = committed
+		then
+			while read -r line
+			do
+				printf "%s\n" "$line"
+			done >actual
+		fi
+	EOF
+	cat >expect <<-EOF &&
+		$ZERO_OID $POST_OID HEAD
+		$ZERO_OID $POST_OID refs/heads/master
+	EOF
+	git update-ref HEAD POST &&
+	test_cmp expect actual
+'
+
+test_expect_success 'hook gets all queued updates in aborted state' '
+	test_when_finished "rm .git/hooks/reference-transaction actual" &&
+	git reset --hard PRE &&
+	write_script .git/hooks/reference-transaction <<-\EOF &&
+		if test "$1" = aborted
+		then
+			while read -r line
+			do
+				printf "%s\n" "$line"
+			done >actual
+		fi
+	EOF
+	cat >expect <<-EOF &&
+		$ZERO_OID $POST_OID HEAD
+		$ZERO_OID $POST_OID refs/heads/master
+	EOF
+	git update-ref --stdin <<-EOF &&
+		start
+		update HEAD POST $ZERO_OID
+		update refs/heads/master POST $ZERO_OID
+		abort
+	EOF
+	test_cmp expect actual
+'
+
+test_done