1 files changed, 195 insertions, 62 deletions

diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index 8266c1fccf..d2ec52bca9 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -38,9 +38,11 @@ static int receive_fsck_objects = -1;
 static int transfer_fsck_objects = -1;
 static int receive_unpack_limit = -1;
 static int transfer_unpack_limit = -1;
+static int advertise_atomic_push = 1;
 static int unpack_limit = 100;
 static int report_status;
 static int use_sideband;
+static int use_atomic;
 static int quiet;
 static int prefer_ofs_delta = 1;
 static int auto_update_server_info;
@@ -67,6 +69,7 @@ static const char *NONCE_SLOP = "SLOP";
 static const char *nonce_status;
 static long nonce_stamp_slop;
 static unsigned long nonce_stamp_slop_limit;
+static struct ref_transaction *transaction;
 
 static enum deny_action parse_deny_action(const char *var, const char *value)
 {
@@ -160,6 +163,11 @@ static int receive_pack_config(const char *var, const char *value, void *cb)
 		return 0;
 	}
 
+	if (strcmp(var, "receive.advertiseatomic") == 0) {
+		advertise_atomic_push = git_config_bool(var, value);
+		return 0;
+	}
+
 	return git_default_config(var, value, cb);
 }
 
@@ -175,6 +183,8 @@ static void show_ref(const char *path, const unsigned char *sha1)
 
 		strbuf_addstr(&cap,
 			      "report-status delete-refs side-band-64k quiet");
+		if (advertise_atomic_push)
+			strbuf_addstr(&cap, " atomic");
 		if (prefer_ofs_delta)
 			strbuf_addstr(&cap, " ofs-delta");
 		if (push_cert_nonce)
@@ -733,7 +743,25 @@ static int update_shallow_ref(struct command *cmd, struct shallow_info *si)
 	return 0;
 }
 
-static const char *update_worktree(unsigned char *sha1)
+/*
+ * NEEDSWORK: we should consolidate various implementions of "are we
+ * on an unborn branch?" test into one, and make the unified one more
+ * robust. !get_sha1() based check used here and elsewhere would not
+ * allow us to tell an unborn branch from corrupt ref, for example.
+ * For the purpose of fixing "deploy-to-update does not work when
+ * pushing into an empty repository" issue, this should suffice for
+ * now.
+ */
+static int head_has_history(void)
+{
+	unsigned char sha1[20];
+
+	return !get_sha1("HEAD", sha1);
+}
+
+static const char *push_to_deploy(unsigned char *sha1,
+				  struct argv_array *env,
+				  const char *work_tree)
 {
 	const char *update_refresh[] = {
 		"update-index", "-q", "--ignore-submodules", "--refresh", NULL
@@ -743,74 +771,95 @@ static const char *update_worktree(unsigned char *sha1)
 	};
 	const char *diff_index[] = {
 		"diff-index", "--quiet", "--cached", "--ignore-submodules",
-		"HEAD", "--", NULL
+		NULL, "--", NULL
 	};
 	const char *read_tree[] = {
 		"read-tree", "-u", "-m", NULL, NULL
 	};
-	const char *work_tree = git_work_tree_cfg ? git_work_tree_cfg : "..";
-	struct argv_array env = ARGV_ARRAY_INIT;
 	struct child_process child = CHILD_PROCESS_INIT;
 
-	if (is_bare_repository())
-		return "denyCurrentBranch = updateInstead needs a worktree";
-
-	argv_array_pushf(&env, "GIT_DIR=%s", absolute_path(get_git_dir()));
-
 	child.argv = update_refresh;
-	child.env = env.argv;
+	child.env = env->argv;
 	child.dir = work_tree;
 	child.no_stdin = 1;
 	child.stdout_to_stderr = 1;
 	child.git_cmd = 1;
-	if (run_command(&child)) {
-		argv_array_clear(&env);
+	if (run_command(&child))
 		return "Up-to-date check failed";
-	}
 
 	/* run_command() does not clean up completely; reinitialize */
 	child_process_init(&child);
 	child.argv = diff_files;
-	child.env = env.argv;
+	child.env = env->argv;
 	child.dir = work_tree;
 	child.no_stdin = 1;
 	child.stdout_to_stderr = 1;
 	child.git_cmd = 1;
-	if (run_command(&child)) {
-		argv_array_clear(&env);
+	if (run_command(&child))
 		return "Working directory has unstaged changes";
-	}
+
+	/* diff-index with either HEAD or an empty tree */
+	diff_index[4] = head_has_history() ? "HEAD" : EMPTY_TREE_SHA1_HEX;
 
 	child_process_init(&child);
 	child.argv = diff_index;
-	child.env = env.argv;
+	child.env = env->argv;
 	child.no_stdin = 1;
 	child.no_stdout = 1;
 	child.stdout_to_stderr = 0;
 	child.git_cmd = 1;
-	if (run_command(&child)) {
-		argv_array_clear(&env);
+	if (run_command(&child))
 		return "Working directory has staged changes";
-	}
 
 	read_tree[3] = sha1_to_hex(sha1);
 	child_process_init(&child);
 	child.argv = read_tree;
-	child.env = env.argv;
+	child.env = env->argv;
 	child.dir = work_tree;
 	child.no_stdin = 1;
 	child.no_stdout = 1;
 	child.stdout_to_stderr = 0;
 	child.git_cmd = 1;
-	if (run_command(&child)) {
-		argv_array_clear(&env);
+	if (run_command(&child))
 		return "Could not update working tree to new HEAD";
-	}
 
-	argv_array_clear(&env);
 	return NULL;
 }
 
+static const char *push_to_checkout_hook = "push-to-checkout";
+
+static const char *push_to_checkout(unsigned char *sha1,
+				    struct argv_array *env,
+				    const char *work_tree)
+{
+	argv_array_pushf(env, "GIT_WORK_TREE=%s", absolute_path(work_tree));
+	if (run_hook_le(env->argv, push_to_checkout_hook,
+			sha1_to_hex(sha1), NULL))
+		return "push-to-checkout hook declined";
+	else
+		return NULL;
+}
+
+static const char *update_worktree(unsigned char *sha1)
+{
+	const char *retval;
+	const char *work_tree = git_work_tree_cfg ? git_work_tree_cfg : "..";
+	struct argv_array env = ARGV_ARRAY_INIT;
+
+	if (is_bare_repository())
+		return "denyCurrentBranch = updateInstead needs a worktree";
+
+	argv_array_pushf(&env, "GIT_DIR=%s", absolute_path(get_git_dir()));
+
+	if (!find_hook(push_to_checkout_hook))
+		retval = push_to_deploy(sha1, &env, work_tree);
+	else
+		retval = push_to_checkout(sha1, &env, work_tree);
+
+	argv_array_clear(&env);
+	return retval;
+}
+
 static const char *update(struct command *cmd, struct shallow_info *si)
 {
 	const char *name = cmd->ref_name;
@@ -910,6 +959,7 @@ static const char *update(struct command *cmd, struct shallow_info *si)
 	}
 
 	if (is_null_sha1(new_sha1)) {
+		struct strbuf err = STRBUF_INIT;
 		if (!parse_object(old_sha1)) {
 			old_sha1 = NULL;
 			if (ref_exists(name)) {
@@ -919,35 +969,35 @@ static const char *update(struct command *cmd, struct shallow_info *si)
 				cmd->did_not_exist = 1;
 			}
 		}
-		if (delete_ref(namespaced_name, old_sha1, 0)) {
-			rp_error("failed to delete %s", name);
+		if (ref_transaction_delete(transaction,
+					   namespaced_name,
+					   old_sha1,
+					   0, "push", &err)) {
+			rp_error("%s", err.buf);
+			strbuf_release(&err);
 			return "failed to delete";
 		}
+		strbuf_release(&err);
 		return NULL; /* good */
 	}
 	else {
 		struct strbuf err = STRBUF_INIT;
-		struct ref_transaction *transaction;
-
 		if (shallow_update && si->shallow_ref[cmd->index] &&
 		    update_shallow_ref(cmd, si))
 			return "shallow error";
 
-		transaction = ref_transaction_begin(&err);
-		if (!transaction ||
-		    ref_transaction_update(transaction, namespaced_name,
-					   new_sha1, old_sha1, 0, 1, "push",
-					   &err) ||
-		    ref_transaction_commit(transaction, &err)) {
-			ref_transaction_free(transaction);
-
+		if (ref_transaction_update(transaction,
+					   namespaced_name,
+					   new_sha1, old_sha1,
+					   0, "push",
+					   &err)) {
 			rp_error("%s", err.buf);
 			strbuf_release(&err);
+
 			return "failed to update ref";
 		}
-
-		ref_transaction_free(transaction);
 		strbuf_release(&err);
+
 		return NULL; /* good */
 	}
 }
@@ -958,7 +1008,7 @@ static void run_update_post_hook(struct command *commands)
 	int argc;
 	const char **argv;
 	struct child_process proc = CHILD_PROCESS_INIT;
-	char *hook;
+	const char *hook;
 
 	hook = find_hook("post-update");
 	for (argc = 0, cmd = commands; cmd; cmd = cmd->next) {
@@ -1131,11 +1181,105 @@ static void reject_updates_to_hidden(struct command *commands)
 	}
 }
 
+static int should_process_cmd(struct command *cmd)
+{
+	return !cmd->error_string && !cmd->skip_update;
+}
+
+static void warn_if_skipped_connectivity_check(struct command *commands,
+					       struct shallow_info *si)
+{
+	struct command *cmd;
+	int checked_connectivity = 1;
+
+	for (cmd = commands; cmd; cmd = cmd->next) {
+		if (should_process_cmd(cmd) && si->shallow_ref[cmd->index]) {
+			error("BUG: connectivity check has not been run on ref %s",
+			      cmd->ref_name);
+			checked_connectivity = 0;
+		}
+	}
+	if (!checked_connectivity)
+		die("BUG: connectivity check skipped???");
+}
+
+static void execute_commands_non_atomic(struct command *commands,
+					struct shallow_info *si)
+{
+	struct command *cmd;
+	struct strbuf err = STRBUF_INIT;
+
+	for (cmd = commands; cmd; cmd = cmd->next) {
+		if (!should_process_cmd(cmd))
+			continue;
+
+		transaction = ref_transaction_begin(&err);
+		if (!transaction) {
+			rp_error("%s", err.buf);
+			strbuf_reset(&err);
+			cmd->error_string = "transaction failed to start";
+			continue;
+		}
+
+		cmd->error_string = update(cmd, si);
+
+		if (!cmd->error_string
+		    && ref_transaction_commit(transaction, &err)) {
+			rp_error("%s", err.buf);
+			strbuf_reset(&err);
+			cmd->error_string = "failed to update ref";
+		}
+		ref_transaction_free(transaction);
+	}
+	strbuf_release(&err);
+}
+
+static void execute_commands_atomic(struct command *commands,
+					struct shallow_info *si)
+{
+	struct command *cmd;
+	struct strbuf err = STRBUF_INIT;
+	const char *reported_error = "atomic push failure";
+
+	transaction = ref_transaction_begin(&err);
+	if (!transaction) {
+		rp_error("%s", err.buf);
+		strbuf_reset(&err);
+		reported_error = "transaction failed to start";
+		goto failure;
+	}
+
+	for (cmd = commands; cmd; cmd = cmd->next) {
+		if (!should_process_cmd(cmd))
+			continue;
+
+		cmd->error_string = update(cmd, si);
+
+		if (cmd->error_string)
+			goto failure;
+	}
+
+	if (ref_transaction_commit(transaction, &err)) {
+		rp_error("%s", err.buf);
+		reported_error = "atomic transaction failed";
+		goto failure;
+	}
+	goto cleanup;
+
+failure:
+	for (cmd = commands; cmd; cmd = cmd->next)
+		if (!cmd->error_string)
+			cmd->error_string = reported_error;
+
+cleanup:
+	ref_transaction_free(transaction);
+	strbuf_release(&err);
+}
+
 static void execute_commands(struct command *commands,
 			     const char *unpacker_error,
 			     struct shallow_info *si)
 {
-	int checked_connectivity;
 	struct command *cmd;
 	unsigned char sha1[20];
 	struct iterate_data data;
@@ -1166,27 +1310,13 @@ static void execute_commands(struct command *commands,
 	free(head_name_to_free);
 	head_name = head_name_to_free = resolve_refdup("HEAD", 0, sha1, NULL);
 
-	checked_connectivity = 1;
-	for (cmd = commands; cmd; cmd = cmd->next) {
-		if (cmd->error_string)
-			continue;
-
-		if (cmd->skip_update)
-			continue;
-
-		cmd->error_string = update(cmd, si);
-		if (shallow_update && !cmd->error_string &&
-		    si->shallow_ref[cmd->index]) {
-			error("BUG: connectivity check has not been run on ref %s",
-			      cmd->ref_name);
-			checked_connectivity = 0;
-		}
-	}
+	if (use_atomic)
+		execute_commands_atomic(commands, si);
+	else
+		execute_commands_non_atomic(commands, si);
 
-	if (shallow_update && !checked_connectivity)
-		error("BUG: run 'git fsck' for safety.\n"
-		      "If there are errors, try to remove "
-		      "the reported refs above");
+	if (shallow_update)
+		warn_if_skipped_connectivity_check(commands, si);
 }
 
 static struct command **queue_command(struct command **tail,
@@ -1268,6 +1398,9 @@ static struct command *read_head_info(struct sha1_array *shallow)
 				use_sideband = LARGE_PACKET_MAX;
 			if (parse_feature_request(feature_list, "quiet"))
 				quiet = 1;
+			if (advertise_atomic_push
+			    && parse_feature_request(feature_list, "atomic"))
+				use_atomic = 1;
 		}
 
 		if (!strcmp(line, "push-cert")) {