[PATCH v2 02/10] promisor-remote: pass config entry to all_fields_match() directly

[Christian Couder <christian.couder@gmail.com>]

The `in_list == 0` path of all_fields_match() looks up the remote in
`config_info` by `advertised->name` repeatedly, even though every
caller in should_accept_remote() has already performed this
lookup and holds the result in `p`.

To avoid this useless work, let's replace the `int in_list`
parameter with a `struct promisor_info *config_entry` pointer:

 - When NULL (ACCEPT_ALL mode): scan the whole `config_info` list, as
   the old `in_list == 1` path did.

 - When non-NULL: match against that single config entry directly,
   avoiding the redundant string_list_lookup() call.

This removes the hidden dependency on `advertised->name` inside
all_fields_match(), which would be wrong if in the future
auto-configured remotes are implemented, as the local config name may
differ from the server's advertised name.

While at it, let's also add a comment before all_fields_match() and
match_field_against_config() to help understand how things work and
help avoid similar issues.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
---
 promisor-remote.c | 36 ++++++++++++++++++++++++------------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/promisor-remote.c b/promisor-remote.c
index 7ce7d22f95..6c935f855a 100644
--- a/promisor-remote.c
+++ b/promisor-remote.c
@@ -575,6 +575,12 @@ enum accept_promisor {
 	ACCEPT_ALL
 };
 
+/*
+ * Check if a specific field and its advertised value match the local
+ * configuration of a given promisor remote.
+ *
+ * Returns 1 if they match, 0 otherwise.
+ */
 static int match_field_against_config(const char *field, const char *value,
 				      struct promisor_info *config_info)
 {
@@ -586,9 +592,18 @@ static int match_field_against_config(const char *field, const char *value,
 	return 0;
 }
 
+/*
+ * Check that the advertised fields match the local configuration.
+ *
+ * When 'config_entry' is NULL (ACCEPT_ALL mode), every checked field
+ * must match at least one remote in 'config_info'.
+ *
+ * When 'config_entry' points to a specific remote's config, the
+ * checked fields are compared against that single remote only.
+ */
 static int all_fields_match(struct promisor_info *advertised,
 			    struct string_list *config_info,
-			    int in_list)
+			    struct promisor_info *config_entry)
 {
 	struct string_list *fields = fields_checked();
 	struct string_list_item *item_checked;
@@ -597,7 +612,6 @@ static int all_fields_match(struct promisor_info *advertised,
 		int match = 0;
 		const char *field = item_checked->string;
 		const char *value = NULL;
-		struct string_list_item *item;
 
 		if (!strcasecmp(field, promisor_field_filter))
 			value = advertised->filter;
@@ -607,7 +621,11 @@ static int all_fields_match(struct promisor_info *advertised,
 		if (!value)
 			return 0;
 
-		if (in_list) {
+		if (config_entry) {
+			match = match_field_against_config(field, value,
+							   config_entry);
+		} else {
+			struct string_list_item *item;
 			for_each_string_list_item(item, config_info) {
 				struct promisor_info *p = item->util;
 				if (match_field_against_config(field, value, p)) {
@@ -615,12 +633,6 @@ static int all_fields_match(struct promisor_info *advertised,
 					break;
 				}
 			}
-		} else {
-			item = string_list_lookup(config_info, advertised->name);
-			if (item) {
-				struct promisor_info *p = item->util;
-				match = match_field_against_config(field, value, p);
-			}
 		}
 
 		if (!match)
@@ -640,7 +652,7 @@ static int should_accept_remote(enum accept_promisor accept,
 	const char *remote_url = advertised->url;
 
 	if (accept == ACCEPT_ALL)
-		return all_fields_match(advertised, config_info, 1);
+		return all_fields_match(advertised, config_info, NULL);
 
 	/* Get config info for that promisor remote */
 	item = string_list_lookup(config_info, remote_name);
@@ -652,7 +664,7 @@ static int should_accept_remote(enum accept_promisor accept,
 	p = item->util;
 
 	if (accept == ACCEPT_KNOWN_NAME)
-		return all_fields_match(advertised, config_info, 0);
+		return all_fields_match(advertised, config_info, p);
 
 	if (accept != ACCEPT_KNOWN_URL)
 		BUG("Unhandled 'enum accept_promisor' value '%d'", accept);
@@ -663,7 +675,7 @@ static int should_accept_remote(enum accept_promisor accept,
 	}
 
 	if (!strcmp(p->url, remote_url))
-		return all_fields_match(advertised, config_info, 0);
+		return all_fields_match(advertised, config_info, p);
 
 	warning(_("known remote named '%s' but with URL '%s' instead of '%s'"),
 		remote_name, p->url, remote_url);
-- 
2.54.0.rc0.114.g05d466edb8