We're about to add a new argument to git-rev-list(1) that allows it to
add all references that are visible when taking `transfer.hideRefs` et
al into account. This will require us to potentially parse multiple sets
of hidden refs, which is not easily possible right now as there is only
a single, global instance of the list of parsed hidden refs.

Refactor `parse_hide_refs_config()` and `ref_is_hidden()` so that both
take the list of hidden references as input and adjust callers to keep a
local list, instead. This allows us to easily use multiple hidden-ref
lists. Furthermore, it allows us to properly free this list before we
exit.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 builtin/receive-pack.c |  8 +++++---
 ls-refs.c              | 13 +++++++++----
 refs.c                 | 14 ++++----------
 refs.h                 |  5 +++--
 upload-pack.c          | 30 ++++++++++++++++++------------
 5 files changed, 39 insertions(+), 31 deletions(-)

diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index 44bcea3a5b..1e24b31a0a 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -80,6 +80,7 @@ static struct object_id push_cert_oid;
 static struct signature_check sigcheck;
 static const char *push_cert_nonce;
 static const char *cert_nonce_seed;
+static struct string_list hidden_refs = STRING_LIST_INIT_DUP;
 
 static const char *NONCE_UNSOLICITED = "UNSOLICITED";
 static const char *NONCE_BAD = "BAD";
@@ -130,7 +131,7 @@ static enum deny_action parse_deny_action(const char *var, const char *value)
 
 static int receive_pack_config(const char *var, const char *value, void *cb)
 {
-	int status = parse_hide_refs_config(var, value, "receive");
+	int status = parse_hide_refs_config(var, value, "receive", &hidden_refs);
 
 	if (status)
 		return status;
@@ -296,7 +297,7 @@ static int show_ref_cb(const char *path_full, const struct object_id *oid,
 	struct oidset *seen = data;
 	const char *path = strip_namespace(path_full);
 
-	if (ref_is_hidden(path, path_full))
+	if (ref_is_hidden(path, path_full, &hidden_refs))
 		return 0;
 
 	/*
@@ -1794,7 +1795,7 @@ static void reject_updates_to_hidden(struct command *commands)
 		strbuf_setlen(&refname_full, prefix_len);
 		strbuf_addstr(&refname_full, cmd->ref_name);
 
-		if (!ref_is_hidden(cmd->ref_name, refname_full.buf))
+		if (!ref_is_hidden(cmd->ref_name, refname_full.buf, &hidden_refs))
 			continue;
 		if (is_null_oid(&cmd->new_oid))
 			cmd->error_string = "deny deleting a hidden ref";
@@ -2591,6 +2592,7 @@ int cmd_receive_pack(int argc, const char **argv, const char *prefix)
 		packet_flush(1);
 	oid_array_clear(&shallow);
 	oid_array_clear(&ref);
+	string_list_clear(&hidden_refs, 0);
 	free((void *)push_cert_nonce);
 	return 0;
 }
diff --git a/ls-refs.c b/ls-refs.c
index fa0d01b47c..fb6769742c 100644
--- a/ls-refs.c
+++ b/ls-refs.c
@@ -6,6 +6,7 @@
 #include "ls-refs.h"
 #include "pkt-line.h"
 #include "config.h"
+#include "string-list.h"
 
 static int config_read;
 static int advertise_unborn;
@@ -73,6 +74,7 @@ struct ls_refs_data {
 	unsigned symrefs;
 	struct strvec prefixes;
 	struct strbuf buf;
+	struct string_list hidden_refs;
 	unsigned unborn : 1;
 };
 
@@ -84,7 +86,7 @@ static int send_ref(const char *refname, const struct object_id *oid,
 
 	strbuf_reset(&data->buf);
 
-	if (ref_is_hidden(refname_nons, refname))
+	if (ref_is_hidden(refname_nons, refname, &data->hidden_refs))
 		return 0;
 
 	if (!ref_match(&data->prefixes, refname_nons))
@@ -137,14 +139,15 @@ static void send_possibly_unborn_head(struct ls_refs_data *data)
 }
 
 static int ls_refs_config(const char *var, const char *value,
-			  void *data UNUSED)
+			  void *cb_data)
 {
+	struct ls_refs_data *data = cb_data;
 	/*
 	 * We only serve fetches over v2 for now, so respect only "uploadpack"
 	 * config. This may need to eventually be expanded to "receive", but we
 	 * don't yet know how that information will be passed to ls-refs.
 	 */
-	return parse_hide_refs_config(var, value, "uploadpack");
+	return parse_hide_refs_config(var, value, "uploadpack", &data->hidden_refs);
 }
 
 int ls_refs(struct repository *r, struct packet_reader *request)
@@ -154,9 +157,10 @@ int ls_refs(struct repository *r, struct packet_reader *request)
 	memset(&data, 0, sizeof(data));
 	strvec_init(&data.prefixes);
 	strbuf_init(&data.buf, 0);
+	string_list_init_dup(&data.hidden_refs);
 
 	ensure_config_read();
-	git_config(ls_refs_config, NULL);
+	git_config(ls_refs_config, &data);
 
 	while (packet_reader_read(request) == PACKET_READ_NORMAL) {
 		const char *arg = request->line;
@@ -195,6 +199,7 @@ int ls_refs(struct repository *r, struct packet_reader *request)
 	packet_fflush(stdout);
 	strvec_clear(&data.prefixes);
 	strbuf_release(&data.buf);
+	string_list_clear(&data.hidden_refs, 0);
 	return 0;
 }
 
diff --git a/refs.c b/refs.c
index a4ab264d74..2c7e88b190 100644
--- a/refs.c
+++ b/refs.c
@@ -1414,9 +1414,8 @@ char *shorten_unambiguous_ref(const char *refname, int strict)
 					    refname, strict);
 }
 
-static struct string_list *hide_refs;
-
-int parse_hide_refs_config(const char *var, const char *value, const char *section)
+int parse_hide_refs_config(const char *var, const char *value, const char *section,
+			   struct string_list *hide_refs)
 {
 	const char *key;
 	if (!strcmp("transfer.hiderefs", var) ||
@@ -1431,21 +1430,16 @@ int parse_hide_refs_config(const char *var, const char *value, const char *secti
 		len = strlen(ref);
 		while (len && ref[len - 1] == '/')
 			ref[--len] = '\0';
-		if (!hide_refs) {
-			CALLOC_ARRAY(hide_refs, 1);
-			hide_refs->strdup_strings = 1;
-		}
 		string_list_append_nodup(hide_refs, ref);
 	}
 	return 0;
 }
 
-int ref_is_hidden(const char *refname, const char *refname_full)
+int ref_is_hidden(const char *refname, const char *refname_full,
+		  const struct string_list *hide_refs)
 {
 	int i;
 
-	if (!hide_refs)
-		return 0;
 	for (i = hide_refs->nr - 1; i >= 0; i--) {
 		const char *match = hide_refs->items[i].string;
 		const char *subject;
diff --git a/refs.h b/refs.h
index 8958717a17..3266fd8f57 100644
--- a/refs.h
+++ b/refs.h
@@ -808,7 +808,8 @@ int update_ref(const char *msg, const char *refname,
 	       const struct object_id *new_oid, const struct object_id *old_oid,
 	       unsigned int flags, enum action_on_err onerr);
 
-int parse_hide_refs_config(const char *var, const char *value, const char *);
+int parse_hide_refs_config(const char *var, const char *value, const char *,
+			   struct string_list *);
 
 /*
  * Check whether a ref is hidden. If no namespace is set, both the first and
@@ -818,7 +819,7 @@ int parse_hide_refs_config(const char *var, const char *value, const char *);
  * the ref is outside that namespace, the first parameter is NULL. The second
  * parameter always points to the full ref name.
  */
-int ref_is_hidden(const char *, const char *);
+int ref_is_hidden(const char *, const char *, const struct string_list *);
 
 /* Is this a per-worktree ref living in the refs/ namespace? */
 int is_per_worktree_ref(const char *refname);
diff --git a/upload-pack.c b/upload-pack.c
index 0b8311bd68..551f22ffa5 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -62,6 +62,7 @@ struct upload_pack_data {
 	struct object_array have_obj;
 	struct oid_array haves;					/* v2 only */
 	struct string_list wanted_refs;				/* v2 only */
+	struct string_list hidden_refs;
 
 	struct object_array shallows;
 	struct string_list deepen_not;
@@ -118,6 +119,7 @@ static void upload_pack_data_init(struct upload_pack_data *data)
 {
 	struct string_list symref = STRING_LIST_INIT_DUP;
 	struct string_list wanted_refs = STRING_LIST_INIT_DUP;
+	struct string_list hidden_refs = STRING_LIST_INIT_DUP;
 	struct object_array want_obj = OBJECT_ARRAY_INIT;
 	struct object_array have_obj = OBJECT_ARRAY_INIT;
 	struct oid_array haves = OID_ARRAY_INIT;
@@ -130,6 +132,7 @@ static void upload_pack_data_init(struct upload_pack_data *data)
 	memset(data, 0, sizeof(*data));
 	data->symref = symref;
 	data->wanted_refs = wanted_refs;
+	data->hidden_refs = hidden_refs;
 	data->want_obj = want_obj;
 	data->have_obj = have_obj;
 	data->haves = haves;
@@ -151,6 +154,7 @@ static void upload_pack_data_clear(struct upload_pack_data *data)
 {
 	string_list_clear(&data->symref, 1);
 	string_list_clear(&data->wanted_refs, 1);
+	string_list_clear(&data->hidden_refs, 0);
 	object_array_clear(&data->want_obj);
 	object_array_clear(&data->have_obj);
 	oid_array_clear(&data->haves);
@@ -842,8 +846,8 @@ static void deepen(struct upload_pack_data *data, int depth)
 		 * Checking for reachable shallows requires that our refs be
 		 * marked with OUR_REF.
 		 */
-		head_ref_namespaced(check_ref, NULL);
-		for_each_namespaced_ref(check_ref, NULL);
+		head_ref_namespaced(check_ref, data);
+		for_each_namespaced_ref(check_ref, data);
 
 		get_reachable_list(data, &reachable_shallows);
 		result = get_shallow_commits(&reachable_shallows,
@@ -1158,11 +1162,11 @@ static void receive_needs(struct upload_pack_data *data,
 
 /* return non-zero if the ref is hidden, otherwise 0 */
 static int mark_our_ref(const char *refname, const char *refname_full,
-			const struct object_id *oid)
+			const struct object_id *oid, const struct string_list *hidden_refs)
 {
 	struct object *o = lookup_unknown_object(the_repository, oid);
 
-	if (ref_is_hidden(refname, refname_full)) {
+	if (ref_is_hidden(refname, refname_full, hidden_refs)) {
 		o->flags |= HIDDEN_REF;
 		return 1;
 	}
@@ -1171,11 +1175,12 @@ static int mark_our_ref(const char *refname, const char *refname_full,
 }
 
 static int check_ref(const char *refname_full, const struct object_id *oid,
-		     int flag UNUSED, void *cb_data UNUSED)
+		     int flag UNUSED, void *cb_data)
 {
 	const char *refname = strip_namespace(refname_full);
+	struct upload_pack_data *data = cb_data;
 
-	mark_our_ref(refname, refname_full, oid);
+	mark_our_ref(refname, refname_full, oid, &data->hidden_refs);
 	return 0;
 }
 
@@ -1204,7 +1209,7 @@ static int send_ref(const char *refname, const struct object_id *oid,
 	struct object_id peeled;
 	struct upload_pack_data *data = cb_data;
 
-	if (mark_our_ref(refname_nons, refname, oid))
+	if (mark_our_ref(refname_nons, refname, oid, &data->hidden_refs))
 		return 0;
 
 	if (capabilities) {
@@ -1327,7 +1332,7 @@ static int upload_pack_config(const char *var, const char *value, void *cb_data)
 	if (parse_object_filter_config(var, value, data) < 0)
 		return -1;
 
-	return parse_hide_refs_config(var, value, "uploadpack");
+	return parse_hide_refs_config(var, value, "uploadpack", &data->hidden_refs);
 }
 
 static int upload_pack_protected_config(const char *var, const char *value, void *cb_data)
@@ -1375,8 +1380,8 @@ void upload_pack(const int advertise_refs, const int stateless_rpc,
 		advertise_shallow_grafts(1);
 		packet_flush(1);
 	} else {
-		head_ref_namespaced(check_ref, NULL);
-		for_each_namespaced_ref(check_ref, NULL);
+		head_ref_namespaced(check_ref, &data);
+		for_each_namespaced_ref(check_ref, &data);
 	}
 
 	if (!advertise_refs) {
@@ -1441,6 +1446,7 @@ static int parse_want(struct packet_writer *writer, const char *line,
 
 static int parse_want_ref(struct packet_writer *writer, const char *line,
 			  struct string_list *wanted_refs,
+			  struct string_list *hidden_refs,
 			  struct object_array *want_obj)
 {
 	const char *refname_nons;
@@ -1451,7 +1457,7 @@ static int parse_want_ref(struct packet_writer *writer, const char *line,
 		struct strbuf refname = STRBUF_INIT;
 
 		strbuf_addf(&refname, "%s%s", get_git_namespace(), refname_nons);
-		if (ref_is_hidden(refname_nons, refname.buf) ||
+		if (ref_is_hidden(refname_nons, refname.buf, hidden_refs) ||
 		    read_ref(refname.buf, &oid)) {
 			packet_writer_error(writer, "unknown ref %s", refname_nons);
 			die("unknown ref %s", refname_nons);
@@ -1508,7 +1514,7 @@ static void process_args(struct packet_reader *request,
 			continue;
 		if (data->allow_ref_in_want &&
 		    parse_want_ref(&data->writer, arg, &data->wanted_refs,
-				   &data->want_obj))
+				   &data->hidden_refs, &data->want_obj))
 			continue;
 		/* process have line */
 		if (parse_have(arg, &data->haves))
-- 
2.38.1