promisor-remote: keep advertised filter in memory

Currently, advertised filters are only kept in memory temporarily
during parsing, or persisted to disk if `promisor.storeFields`
contains 'partialCloneFilter'.

In a following commit though, we will add a `--filter=auto` option.
This option will enable the client to use the filters that the server
is suggesting for the promisor remotes the client accepts.

To use them even if `promisor.storeFields` is not configured, these
filters should be stored somewhere for the current session.

Let's add an `advertised_filter` field to `struct promisor_remote`
for that purpose.

To ensure that the filters are available in all cases,
filter_promisor_remote() captures them into a temporary list and
applies them to the `promisor_remote` structs after the potential
configuration reload.

Then the accepted remotes are marked as `accepted` in the repository
state. This ensures that subsequent calls to look up accepted remotes
(like in the filter construction below) actually find them.

In a following commit, we will add a `--filter=auto` option that will
enable a client to use the filters suggested by the server for the
promisor remotes the client accepted.

To enable the client to construct a filter spec based on these filters,
let's add a `promisor_remote_construct_filter(repo)` function.

This function:

- iterates over all accepted promisor remotes in the repository,
- collects the filters advertised for them (using `advertised_filter`
  which a previous commit added to `struct promisor_remote`), and
- generates a single filter spec for them (using the
  `list_objects_filter_combine()` function added by a previous commit).

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

promisor-remote.c

@@ -193,6 +193,7 @@ void promisor_remote_clear(struct promisor_remote_config *config)
 	while (config->promisors) {
 		struct promisor_remote *r = config->promisors;
 		free(r->partial_clone_filter);
+		free(r->advertised_filter);
 		config->promisors = config->promisors->next;
 		free(r);
 	}
@@ -837,6 +838,7 @@ static void filter_promisor_remote(struct repository *repo,
 	struct store_info *store_info = NULL;
 	struct string_list_item *item;
 	bool reload_config = false;
+	struct string_list captured_filters = STRING_LIST_INIT_DUP;
 
 	if (!repo_config_get_string_tmp(the_repository, "promisor.acceptfromserver", &accept_str)) {
 		if (!*accept_str || !strcasecmp("None", accept_str))
@@ -879,6 +881,13 @@ static void filter_promisor_remote(struct repository *repo,
 				reload_config = true;
 
 			strvec_push(accepted, advertised->name);
+
+			/* Capture advertised filters for accepted remotes */
+			if (advertised->filter) {
+				struct string_list_item *i;
+				i = string_list_append(&captured_filters, advertised->name);
+				i->util = xstrdup(advertised->filter);
+			}
 		}
 
 		promisor_info_free(advertised);
@@ -890,6 +899,25 @@ static void filter_promisor_remote(struct repository *repo,
 
 	if (reload_config)
 		repo_promisor_remote_reinit(repo);
+
+	/* Apply captured filters to the stable repo state */
+	for_each_string_list_item(item, &captured_filters) {
+		struct promisor_remote *r = repo_promisor_remote_find(repo, item->string);
+		if (r) {
+			free(r->advertised_filter);
+			r->advertised_filter = item->util;
+			item->util = NULL;
+		}
+	}
+
+	string_list_clear(&captured_filters, 1);
+
+	/* Mark the remotes as accepted in the repository state */
+	for (size_t i = 0; i < accepted->nr; i++) {
+		struct promisor_remote *r = repo_promisor_remote_find(repo, accepted->v[i]);
+		if (r)
+			r->accepted = 1;
+	}
 }
 
 char *promisor_remote_reply(const char *info)
@@ -935,3 +963,23 @@ void mark_promisor_remotes_as_accepted(struct repository *r, const char *remotes
 
 	string_list_clear(&accepted_remotes, 0);
 }
+
+char *promisor_remote_construct_filter(struct repository *repo)
+{
+	struct string_list advertised_filters = STRING_LIST_INIT_NODUP;
+	struct promisor_remote *r;
+	char *result;
+
+	promisor_remote_init(repo);
+
+	for (r = repo->promisor_remote_config->promisors; r; r = r->next) {
+		if (r->accepted && r->advertised_filter)
+			string_list_append(&advertised_filters, r->advertised_filter);
+	}
+
+	result = list_objects_filter_combine(&advertised_filters);
+
+	string_list_clear(&advertised_filters, 0);
+
+	return result;
+}

promisor-remote.h

@@ -15,6 +15,7 @@ struct object_id;
 struct promisor_remote {
 	struct promisor_remote *next;
 	char *partial_clone_filter;
+	char *advertised_filter;
 	unsigned int accepted : 1;
 	const char name[FLEX_ARRAY];
 };
@@ -67,4 +68,9 @@ void mark_promisor_remotes_as_accepted(struct repository *repo, const char *remo
  */
 int repo_has_accepted_promisor_remote(struct repository *r);
 
+/*
+ * Use the filters from the accepted remotes to create a filter.
+ */
+char *promisor_remote_construct_filter(struct repository *repo);
+
 #endif /* PROMISOR_REMOTE_H */