remote: add remote.*.negotiationRestrict config

In a previous change, the --negotiation-restrict command-line option of 'git
fetch' was added as a synonym of --negotiation-tip. Both of these options
restrict the set of 'haves' the client can send as part of negotiation.

This was previously not available via a configuration option. Add a new
'remote.<name>.negotiationRestrict' multi-valued config option that updates
'git fetch <name>' to use these restrictions by default.

If the user provides even one --negotiation-restrict argument, then the
config is ignored.

An empty value resets the value list to allow ignoring earlier config
values, such as those that might be set in system or global config.

Reviewed-by: Matthew John Cheetham <mjcheetham@outlook.com>
Signed-off-by: Derrick Stolee <stolee@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config/remote.adoc

@@ -107,6 +107,24 @@ priority configuration file (e.g. `.git/config` in a repository) to clear
 the values inherited from a lower priority configuration files (e.g.
 `$HOME/.gitconfig`).
 
+remote.<name>.negotiationRestrict::
+	When negotiating with this remote during `git fetch`, restrict the
+	commits advertised as "have" lines to only those reachable from refs
+	matching the given patterns.  This multi-valued config option behaves
+	like `--negotiation-restrict` on the command line.
++
+Each value is either an exact ref name (e.g. `refs/heads/release`) or a
+glob pattern (e.g. `refs/heads/release/*`).  The pattern syntax is the
+same as for `--negotiation-restrict`.
++
+These config values are used as defaults for the `--negotiation-restrict`
+command-line option.  If `--negotiation-restrict` (or its synonym
+`--negotiation-tip`) is specified on the command line, then the config
+values are not used.
++
+Blank values signal to ignore all previous values, allowing a reset of
+the list from broader config scenarios.
+
 remote.<name>.followRemoteHEAD::
 	How linkgit:git-fetch[1] should handle updates to `remotes/<name>/HEAD`
 	when fetching using the configured refspecs of a remote.

builtin/fetch.c

@@ -1601,6 +1601,19 @@ static struct transport *prepare_transport(struct remote *remote, int deepen,
 		else
 			warning(_("ignoring %s because the protocol does not support it"),
 				"--negotiation-restrict");
+	} else if (remote->negotiation_restrict.nr) {
+		struct string_list_item *item;
+		for_each_string_list_item(item, &remote->negotiation_restrict)
+			string_list_append(&negotiation_restrict, item->string);
+		if (transport->smart_options)
+			add_negotiation_restrict_tips(transport->smart_options);
+		else {
+			struct strbuf config_name = STRBUF_INIT;
+			strbuf_addf(&config_name, "remote.%s.negotiationRestrict", remote->name);
+			warning(_("ignoring %s because the protocol does not support it"),
+				config_name.buf);
+			strbuf_release(&config_name);
+		}
 	}
 	return transport;
 }
@@ -2658,10 +2671,6 @@ int cmd_fetch(int argc,
 		config.display_format = DISPLAY_FORMAT_PORCELAIN;
 	}
 
-	if (negotiate_only && !negotiation_restrict.nr)
-		die(_("%s needs one or more %s"), "--negotiate-only",
-		    "--negotiation-restrict=*");
-
 	if (deepen_relative) {
 		if (deepen_relative < 0)
 			die(_("negative depth in --deepen is not supported"));
@@ -2749,14 +2758,19 @@ int cmd_fetch(int argc,
 		if (!remote)
 			die(_("must supply remote when using --negotiate-only"));
 		gtransport = prepare_transport(remote, 1, &filter_options);
-		if (gtransport->smart_options) {
-			gtransport->smart_options->acked_commits = &acked_commits;
-		} else {
+
+		if (!gtransport->smart_options) {
 			warning(_("protocol does not support --negotiate-only, exiting"));
 			result = 1;
 			trace2_region_leave("fetch", "negotiate-only", the_repository);
 			goto cleanup;
 		}
+		if (!gtransport->smart_options->negotiation_restrict_tips)
+			die(_("%s needs one or more %s"), "--negotiate-only",
+			    "--negotiation-restrict=*");
+
+		gtransport->smart_options->acked_commits = &acked_commits;
+
 		if (server_options.nr)
 			gtransport->server_options = &server_options;
 		result = transport_fetch_refs(gtransport, NULL);

remote.c

@@ -152,6 +152,7 @@ static struct remote *make_remote(struct remote_state *remote_state,
 	refspec_init_push(&ret->push);
 	refspec_init_fetch(&ret->fetch);
 	string_list_init_dup(&ret->server_options);
+	string_list_init_dup(&ret->negotiation_restrict);
 
 	ALLOC_GROW(remote_state->remotes, remote_state->remotes_nr + 1,
 		   remote_state->remotes_alloc);
@@ -179,6 +180,7 @@ static void remote_clear(struct remote *remote)
 	FREE_AND_NULL(remote->http_proxy);
 	FREE_AND_NULL(remote->http_proxy_authmethod);
 	string_list_clear(&remote->server_options, 0);
+	string_list_clear(&remote->negotiation_restrict, 0);
 }
 
 static void add_merge(struct branch *branch, const char *name)
@@ -562,6 +564,9 @@ static int handle_config(const char *key, const char *value,
 	} else if (!strcmp(subkey, "serveroption")) {
 		return parse_transport_option(key, value,
 					      &remote->server_options);
+	} else if (!strcmp(subkey, "negotiationrestrict")) {
+		return parse_transport_option(key, value,
+					      &remote->negotiation_restrict);
 	} else if (!strcmp(subkey, "followremotehead")) {
 		const char *no_warn_branch;
 		if (!strcmp(value, "never"))

remote.h

@@ -117,6 +117,7 @@ struct remote {
 	char *http_proxy_authmethod;
 
 	struct string_list server_options;
+	struct string_list negotiation_restrict;
 
 	enum follow_remote_head_settings follow_remote_head;
 	const char *no_warn_branch;

t/t5510-fetch.sh

@@ -1485,6 +1485,32 @@ test_expect_success '--negotiation-restrict and --negotiation-tip can be mixed'
 	check_negotiation_tip
 '
 
+test_expect_success 'remote.<name>.negotiationRestrict used as default' '
+	setup_negotiation_tip server server 0 &&
+
+	# test the reset of the list on an empty value
+	git -C client config --add remote.origin.negotiationRestrict alpha_2 &&
+	git -C client config --add remote.origin.negotiationRestrict "" &&
+	git -C client config --add remote.origin.negotiationRestrict alpha_1 &&
+	git -C client config --add remote.origin.negotiationRestrict beta_1 &&
+	GIT_TRACE_PACKET="$(pwd)/trace" git -C client fetch \
+		origin alpha_s beta_s &&
+	check_negotiation_tip
+'
+
+test_expect_success 'CLI --negotiation-restrict overrides remote config' '
+	setup_negotiation_tip server server 0 &&
+	git -C client config --add remote.origin.negotiationRestrict alpha_1 &&
+	git -C client config --add remote.origin.negotiationRestrict beta_1 &&
+	ALPHA_1=$(git -C client rev-parse alpha_1) &&
+	GIT_TRACE_PACKET="$(pwd)/trace" git -C client fetch \
+		--negotiation-restrict=alpha_1 \
+		origin alpha_s beta_s &&
+	test_grep "fetch> have $ALPHA_1" trace &&
+	BETA_1=$(git -C client rev-parse beta_1) &&
+	test_grep ! "fetch> have $BETA_1" trace
+'
+
 test_expect_success SYMLINKS 'clone does not get confused by a D/F conflict' '
 	git init df-conflict &&
 	(