fetch: rework negotiation tip options

Documentation/config/remote.adoc

@@ -107,6 +107,46 @@ 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` and `git push`,
+	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.
+
+remote.<name>.negotiationRequire::
+	When negotiating with this remote during `git fetch` and `git push`,
+	the client advertises a list of commits that exist locally.  In
+	repos with many references, this list of "haves" can be truncated.
+	Depending on data shape, dropping certain references may be
+	expensive.  This multi-valued config option specifies ref patterns
+	whose tips should always be sent as "have" commits during fetch
+	negotiation with this remote.
++
+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-require`
+command-line option.  If `--negotiation-require` is specified on the
+command line, then the config values are not used.
++
+This option is additive with the normal negotiation process: the
+negotiation algorithm still runs and advertises its own selected commits,
+but the refs matching `remote.<name>.negotiationRequire` are sent
+unconditionally on top of those heuristically selected commits.  This
+option is also used during push negotiation when `push.negotiate` is
+enabled.
+
 remote.<name>.followRemoteHEAD::
 	How linkgit:git-fetch[1] should handle updates to `remotes/<name>/HEAD`
 	when fetching using the configured refspecs of a remote.

Documentation/fetch-options.adoc

@@ -49,6 +49,7 @@ the current repository has the same history as the source repository.
 	`.git/shallow`. This option updates `.git/shallow` and accepts such
 	refs.
 
+`--negotiation-restrict=(<commit>|<glob>)`::
 `--negotiation-tip=(<commit>|<glob>)`::
 	By default, Git will report, to the server, commits reachable
 	from all local refs to find common commits in an attempt to
@@ -58,6 +59,9 @@ the current repository has the same history as the source repository.
 	local ref is likely to have commits in common with the
 	upstream ref being fetched.
 +
+`--negotiation-restrict` is the preferred name for this option;
+`--negotiation-tip` is accepted as a synonym.
++
 This option may be specified more than once; if so, Git will report
 commits reachable from any of the given commits.
 +
@@ -69,6 +73,29 @@ See also the `fetch.negotiationAlgorithm` and `push.negotiate`
 configuration variables documented in linkgit:git-config[1], and the
 `--negotiate-only` option below.
 
+`--negotiation-require=<revision>`::
+	Ensure that the given ref tip is always sent as a "have" line
+	during fetch negotiation, regardless of what the negotiation
+	algorithm selects.  This is useful to guarantee that common
+	history reachable from specific refs is always considered, even
+	when `--negotiation-restrict` restricts the set of tips or when
+	the negotiation algorithm would otherwise skip them.
++
+This option may be specified more than once; if so, each ref is sent
+unconditionally.
++
+The argument may be an exact ref name (e.g. `refs/heads/release`) or a
+glob pattern (e.g. `refs/heads/release/{asterisk}`).  The pattern syntax
+is the same as for `--negotiation-restrict`.
++
+If `--negotiation-restrict` is used, the have set is first restricted by
+that option and then increased to include the tips specified by
+`--negotiation-require`.
++
+If this option is not specified on the command line, then any
+`remote.<name>.negotiationRequire` config values for the current remote
+are used instead.
+
 `--negotiate-only`::
 	Do not fetch anything from the server, and instead print the
 	ancestors of the provided `--negotiation-tip=` arguments,

builtin/fetch.c

@@ -99,6 +99,7 @@ static struct transport *gsecondary;
 static struct refspec refmap = REFSPEC_INIT_FETCH;
 static struct string_list server_options = STRING_LIST_INIT_DUP;
 static struct string_list negotiation_tip = STRING_LIST_INIT_NODUP;
+static struct string_list negotiation_require = STRING_LIST_INIT_NODUP;
 
 struct fetch_config {
 	enum display_format display_format;
@@ -1534,7 +1535,7 @@ static int add_oid(const struct reference *ref, void *cb_data)
 	return 0;
 }
 
-static void add_negotiation_tips(struct git_transport_options *smart_options)
+static void add_negotiation_restrict_tips(struct git_transport_options *smart_options)
 {
 	struct oid_array *oids = xcalloc(1, sizeof(*oids));
 	int i;
@@ -1558,10 +1559,10 @@ static void add_negotiation_tips(struct git_transport_options *smart_options)
 		refs_for_each_ref_ext(get_main_ref_store(the_repository),
 				      add_oid, oids, &opts);
 		if (old_nr == oids->nr)
-			warning("ignoring --negotiation-tip=%s because it does not match any refs",
-				s);
+			warning(_("ignoring %s=%s because it does not match any refs"),
+				"--negotiation-restrict", s);
 	}
-	smart_options->negotiation_tips = oids;
+	smart_options->negotiation_restrict_tips = oids;
 }
 
 static struct transport *prepare_transport(struct remote *remote, int deepen,
@@ -1597,9 +1598,40 @@ static struct transport *prepare_transport(struct remote *remote, int deepen,
 	}
 	if (negotiation_tip.nr) {
 		if (transport->smart_options)
-			add_negotiation_tips(transport->smart_options);
+			add_negotiation_restrict_tips(transport->smart_options);
 		else
-			warning("ignoring --negotiation-tip because the protocol does not support it");
+			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_tip, 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);
+		}
+	}
+	if (negotiation_require.nr) {
+		if (transport->smart_options)
+			transport->smart_options->negotiation_require = &negotiation_require;
+		else
+			warning(_("ignoring %s because the protocol does not support it"),
+				"--negotiation-require");
+	} else if (remote->negotiation_require.nr) {
+		if (transport->smart_options) {
+			transport->smart_options->negotiation_require = &remote->negotiation_require;
+		} else {
+			struct strbuf config_name = STRBUF_INIT;
+			strbuf_addf(&config_name, "remote.%s.negotiationRequire", remote->name);
+			warning(_("ignoring %s because the protocol does not support it"),
+				config_name.buf);
+			strbuf_release(&config_name);
+		}
 	}
 	return transport;
 }
@@ -2567,6 +2599,10 @@ int cmd_fetch(int argc,
 		OPT_IPVERSION(&family),
 		OPT_STRING_LIST(0, "negotiation-tip", &negotiation_tip, N_("revision"),
 				N_("report that we have only objects reachable from this object")),
+		OPT_STRING_LIST(0, "negotiation-restrict", &negotiation_tip, N_("revision"),
+				N_("report that we have only objects reachable from this object")),
+		OPT_STRING_LIST(0, "negotiation-require", &negotiation_require, N_("revision"),
+				N_("ensure this ref is always sent as a negotiation have")),
 		OPT_BOOL(0, "negotiate-only", &negotiate_only,
 			 N_("do not fetch a packfile; instead, print ancestors of negotiation tips")),
 		OPT_PARSE_LIST_OBJECTS_FILTER(&filter_options),
@@ -2656,8 +2692,12 @@ int cmd_fetch(int argc,
 		config.display_format = DISPLAY_FORMAT_PORCELAIN;
 	}
 
-	if (negotiate_only && !negotiation_tip.nr)
-		die(_("--negotiate-only needs one or more --negotiation-tip=*"));
+	if (negotiate_only && !negotiation_tip.nr) {
+		/*
+		 * Defer this check: remote.<name>.negotiationRestrict may
+		 * provide defaults in prepare_transport().
+		 */
+	}
 
 	if (deepen_relative) {
 		if (deepen_relative < 0)
@@ -2746,6 +2786,9 @@ 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->negotiation_restrict_tips)
+			die(_("--negotiate-only needs one or more --negotiation-restrict=*"));
 		if (gtransport->smart_options) {
 			gtransport->smart_options->acked_commits = &acked_commits;
 		} else {

builtin/pull.c

@@ -999,6 +999,12 @@ int cmd_pull(int argc,
 		OPT_PASSTHRU_ARGV(0, "negotiation-tip", &opt_fetch, N_("revision"),
 			N_("report that we have only objects reachable from this object"),
 			0),
+		OPT_PASSTHRU_ARGV(0, "negotiation-restrict", &opt_fetch, N_("revision"),
+			N_("report that we have only objects reachable from this object"),
+			0),
+		OPT_PASSTHRU_ARGV(0, "negotiation-require", &opt_fetch, N_("revision"),
+			N_("ensure this ref is always sent as a negotiation have"),
+			0),
 		OPT_BOOL(0, "show-forced-updates", &opt_show_forced_updates,
 			 N_("check for forced-updates on all updated branches")),
 		OPT_PASSTHRU(0, "set-upstream", &set_upstream, NULL,