[PATCH v2 1/3] promisor-remote: refactor to get rid of 'struct strvec'

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

In a following commit, we will use the new 'promisor-remote' protocol
capability introduced by d460267613 (Add 'promisor-remote' capability
to protocol v2, 2025-02-18) to pass and process more information
about promisor remotes than just their name and url.

For that purpose, we will need to store information about other
fields, especially information that might or might not be available
for different promisor remotes. Unfortunately using 'struct strvec',
as we currently do, to store information about the promisor remotes
with one 'struct strvec' for each field like "name" or "url" does not
scale easily in that case.

Let's refactor this and introduce a new 'struct promisor_info' linked
list that contains a 'struct string_list fields'. This string_list
stores the field names, like "name" and "url", in the 'string' member
of its items, and the field values in the 'util' member of its items.

Except for "name", each "<field_name>/<field_value>" pair should
correspond to a "remote.<name>.<field_name>" config variable set to
<field_value> where "<name>" is a promisor remote name.

Previously in Git, the part after the last dot in a configuration
variable key, for example "c" for "a.b.c", was called the "variable
name part" of a configuration key. It would be very confusing to use
"variable name part" or some similar terms in the context of the
'promisor-remote' protocol though, so let's forget about it, and just
use "field", "field name" and "field value" instead.

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
---
 promisor-remote.c | 142 ++++++++++++++++++++++++++++++++++------------
 1 file changed, 105 insertions(+), 37 deletions(-)

diff --git a/promisor-remote.c b/promisor-remote.c
index 5801ebfd9b..24d0e70132 100644
--- a/promisor-remote.c
+++ b/promisor-remote.c
@@ -314,10 +314,51 @@ static int allow_unsanitized(char ch)
 	return ch > 32 && ch < 127;
 }
 
-static void promisor_info_vecs(struct repository *repo,
-			       struct strvec *names,
-			       struct strvec *urls)
+/*
+ * Linked list for promisor remotes involved in the "promisor-remote"
+ * protocol capability.
+ *
+ * 'fields' contains a defined set of field name/value pairs for
+ * each promisor remote. Field names are stored in the 'string'
+ * member, and values in the 'util' member.
+ *
+ * Currently supported field names:
+ * - "name": The name of the promisor remote.
+ * - "url": The URL of the promisor remote.
+ *
+ * Except for "name", each "<field_name>/<field_value>" pair should
+ * correspond to a "remote.<name>.<field_name>" config variable set to
+ * <field_value> where "<name>" is a promisor remote name.
+ *
+ * 'fields' should not be sorted, as we will rely on the order we put
+ * things into it. So, for example, 'string_list_append()' should be
+ * used instead of 'string_list_insert()'.
+ */
+struct promisor_info {
+	struct promisor_info *next;
+	struct string_list fields;
+};
+
+static void promisor_info_list_free(struct promisor_info *p)
+{
+	struct promisor_info *next;
+
+	for (; p; p = next) {
+		next = p->next;
+		string_list_clear(&p->fields, 0);
+		free(p);
+	}
+}
+
+/*
+ * Prepare a 'struct promisor_info' linked list of promisor
+ * remotes. For each promisor remote, some of its fields, starting
+ * with "name" and "url", are put in the 'fields' string_list.
+ */
+static struct promisor_info *promisor_info_list(struct repository *repo)
 {
+	struct promisor_info *infos = NULL;
+	struct promisor_info **last_info = &infos;
 	struct promisor_remote *r;
 
 	promisor_remote_init(repo);
@@ -328,57 +369,78 @@ static void promisor_info_vecs(struct repository *repo,
 
 		/* Only add remotes with a non empty URL */
 		if (!git_config_get_string_tmp(url_key, &url) && *url) {
-			strvec_push(names, r->name);
-			strvec_push(urls, url);
+			struct promisor_info *new_info = xcalloc(1, sizeof(*new_info));
+
+			string_list_init_dup(&new_info->fields);
+			new_info->fields.cmp = strcasecmp;
+
+			string_list_append(&new_info->fields, "name")->util = (char *)r->name;
+			string_list_append(&new_info->fields, "url")->util = (char *)url;
+
+			*last_info = new_info;
+			last_info = &new_info->next;
 		}
 
 		free(url_key);
 	}
+
+	return infos;
 }
 
 char *promisor_remote_info(struct repository *repo)
 {
 	struct strbuf sb = STRBUF_INIT;
 	int advertise_promisors = 0;
-	struct strvec names = STRVEC_INIT;
-	struct strvec urls = STRVEC_INIT;
+	struct promisor_info *info_list;
+	struct promisor_info *r;
 
 	git_config_get_bool("promisor.advertise", &advertise_promisors);
 
 	if (!advertise_promisors)
 		return NULL;
 
-	promisor_info_vecs(repo, &names, &urls);
+	info_list = promisor_info_list(repo);
 
-	if (!names.nr)
+	if (!info_list)
 		return NULL;
 
-	for (size_t i = 0; i < names.nr; i++) {
-		if (i)
+	for (r = info_list; r; r = r->next) {
+		struct string_list_item *item;
+		int first = 1;
+
+		if (r != info_list)
 			strbuf_addch(&sb, ';');
-		strbuf_addstr(&sb, "name=");
-		strbuf_addstr_urlencode(&sb, names.v[i], allow_unsanitized);
-		strbuf_addstr(&sb, ",url=");
-		strbuf_addstr_urlencode(&sb, urls.v[i], allow_unsanitized);
+
+		for_each_string_list_item(item, &r->fields) {
+			if (first)
+				first = 0;
+			else
+				strbuf_addch(&sb, ',');
+			strbuf_addf(&sb, "%s=", item->string);
+			strbuf_addstr_urlencode(&sb, (char *)item->util, allow_unsanitized);
+		}
 	}
 
-	strvec_clear(&names);
-	strvec_clear(&urls);
+	promisor_info_list_free(info_list);
 
 	return strbuf_detach(&sb, NULL);
 }
 
 /*
- * Find first index of 'nicks' where there is 'nick'. 'nick' is
- * compared case sensitively to the strings in 'nicks'. If not found
- * 'nicks->nr' is returned.
+ * Find first element of 'p' where the 'name' field is 'nick'. 'nick'
+ * is compared case sensitively to the strings in 'p'. If not found
+ * NULL is returned.
  */
-static size_t remote_nick_find(struct strvec *nicks, const char *nick)
+static struct promisor_info *remote_nick_find(struct promisor_info *p, const char *nick)
 {
-	for (size_t i = 0; i < nicks->nr; i++)
-		if (!strcmp(nicks->v[i], nick))
-			return i;
-	return nicks->nr;
+	for (; p; p = p->next) {
+		if (strcmp(p->fields.items[0].string, "name"))
+			BUG("First field of promisor info should be 'name', but was '%s'.",
+			    p->fields.items[0].string);
+		if (!strcmp(p->fields.items[0].util, nick))
+			return p;
+	}
+	return NULL;
 }
 
 enum accept_promisor {
@@ -390,16 +452,17 @@ enum accept_promisor {
 
 static int should_accept_remote(enum accept_promisor accept,
 				const char *remote_name, const char *remote_url,
-				struct strvec *names, struct strvec *urls)
+				struct promisor_info *info_list)
 {
-	size_t i;
+	struct promisor_info *p;
+	const char *local_url;
 
 	if (accept == ACCEPT_ALL)
 		return 1;
 
-	i = remote_nick_find(names, remote_name);
+	p = remote_nick_find(info_list, remote_name);
 
-	if (i >= names->nr)
+	if (!p)
 		/* We don't know about that remote */
 		return 0;
 
@@ -414,11 +477,18 @@ static int should_accept_remote(enum accept_promisor accept,
 		return 0;
 	}
 
-	if (!strcmp(urls->v[i], remote_url))
+	if (strcmp(p->fields.items[1].string, "url"))
+		BUG("Bad info_list for remote '%s'.\n"
+		    "Second field of promisor info should be 'url', but was '%s'.",
+		    remote_name, p->fields.items[1].string);
+
+	local_url = p->fields.items[1].util;
+
+	if (!strcmp(local_url, remote_url))
 		return 1;
 
 	warning(_("known remote named '%s' but with URL '%s' instead of '%s'"),
-		remote_name, urls->v[i], remote_url);
+		remote_name, local_url, remote_url);
 
 	return 0;
 }
@@ -430,8 +500,7 @@ static void filter_promisor_remote(struct repository *repo,
 	struct strbuf **remotes;
 	const char *accept_str;
 	enum accept_promisor accept = ACCEPT_NONE;
-	struct strvec names = STRVEC_INIT;
-	struct strvec urls = STRVEC_INIT;
+	struct promisor_info *info_list = NULL;
 
 	if (!git_config_get_string_tmp("promisor.acceptfromserver", &accept_str)) {
 		if (!*accept_str || !strcasecmp("None", accept_str))
@@ -451,7 +520,7 @@ static void filter_promisor_remote(struct repository *repo,
 		return;
 
 	if (accept != ACCEPT_ALL)
-		promisor_info_vecs(repo, &names, &urls);
+		info_list = promisor_info_list(repo);
 
 	/* Parse remote info received */
 
@@ -482,7 +551,7 @@ static void filter_promisor_remote(struct repository *repo,
 		if (remote_url)
 			decoded_url = url_percent_decode(remote_url);
 
-		if (decoded_name && should_accept_remote(accept, decoded_name, decoded_url, &names, &urls))
+		if (decoded_name && should_accept_remote(accept, decoded_name, decoded_url, info_list))
 			strvec_push(accepted, decoded_name);
 
 		strbuf_list_free(elems);
@@ -490,8 +559,7 @@ static void filter_promisor_remote(struct repository *repo,
 		free(decoded_url);
 	}
 
-	strvec_clear(&names);
-	strvec_clear(&urls);
+	promisor_info_list_free(info_list);
 	strbuf_list_free(remotes);
 }
 
-- 
2.49.0.157.g09af0369a6