Merge branch 'jc/optional-path'

"git config get --path" segfaulted on an ":(optional)path" that
does not exist, which has been corrected.

* jc/optional-path:
  config: really treat missing optional path as not configured
  config: really pretend missing :(optional) value is not there
  config: mark otherwise unused function as file-scope static

builtin/blame.c

@@ -739,7 +739,8 @@ static int git_blame_config(const char *var, const char *value,
 		ret = git_config_pathname(&str, var, value);
 		if (ret)
 			return ret;
-		string_list_insert(&ignore_revs_file_list, str);
+		if (str)
+			string_list_insert(&ignore_revs_file_list, str);
 		free(str);
 		return 0;
 	}

builtin/config.c

@@ -261,6 +261,12 @@ struct strbuf_list {
 	int alloc;
 };
 
+/*
+ * Format the configuration key-value pair (`key_`, `value_`) and
+ * append it into strbuf `buf`.  Returns a negative value on failure,
+ * 0 on success, 1 on a missing optional value (i.e., telling the
+ * caller to pretend that <key_,value_> did not exist).
+ */
 static int format_config(const struct config_display_options *opts,
 			 struct strbuf *buf, const char *key_,
 			 const char *value_, const struct key_value_info *kvi)
@@ -299,7 +305,10 @@ static int format_config(const struct config_display_options *opts,
 			char *v;
 			if (git_config_pathname(&v, key_, value_) < 0)
 				return -1;
-			strbuf_addstr(buf, v);
+			if (v)
+				strbuf_addstr(buf, v);
+			else
+				return 1; /* :(optional)no-such-file */
 			free((char *)v);
 		} else if (opts->type == TYPE_EXPIRY_DATE) {
 			timestamp_t t;
@@ -344,6 +353,7 @@ static int collect_config(const char *key_, const char *value_,
 	struct collect_config_data *data = cb;
 	struct strbuf_list *values = data->values;
 	const struct key_value_info *kvi = ctx->kvi;
+	int status;
 
 	if (!(data->get_value_flags & GET_VALUE_KEY_REGEXP) &&
 	    strcmp(key_, data->key))
@@ -361,8 +371,15 @@ static int collect_config(const char *key_, const char *value_,
 	ALLOC_GROW(values->items, values->nr + 1, values->alloc);
 	strbuf_init(&values->items[values->nr], 0);
 
-	return format_config(data->display_opts, &values->items[values->nr++],
+	status = format_config(data->display_opts, &values->items[values->nr++],
-			     key_, value_, kvi);
+			       key_, value_, kvi);
+	if (status < 0)
+		return status;
+	if (status) {
+		strbuf_release(&values->items[--values->nr]);
+		status = 0;
+	}
+	return status;
 }
 
 static int get_value(const struct config_location_options *opts,
@@ -438,15 +455,23 @@ static int get_value(const struct config_location_options *opts,
 	if (!values.nr && display_opts->default_value) {
 		struct key_value_info kvi = KVI_INIT;
 		struct strbuf *item;
+		int status;
 
 		kvi_from_param(&kvi);
 		ALLOC_GROW(values.items, values.nr + 1, values.alloc);
 		item = &values.items[values.nr++];
 		strbuf_init(item, 0);
-		if (format_config(display_opts, item, key_,
+
-				  display_opts->default_value, &kvi) < 0)
+		status = format_config(display_opts, item, key_,
+				       display_opts->default_value, &kvi);
+		if (status < 0)
 			die(_("failed to format default config value: %s"),
 			    display_opts->default_value);
+		if (status) {
+			/* default was a missing optional value */
+			values.nr--;
+			strbuf_release(item);
+		}
 	}
 
 	ret = !values.nr;
@@ -714,11 +739,13 @@ static int get_urlmatch(const struct config_location_options *opts,
 	for_each_string_list_item(item, &values) {
 		struct urlmatch_current_candidate_value *matched = item->util;
 		struct strbuf buf = STRBUF_INIT;
+		int status;
 
-		format_config(&display_opts, &buf, item->string,
+		status = format_config(&display_opts, &buf, item->string,
-			      matched->value_is_null ? NULL : matched->value.buf,
+				       matched->value_is_null ? NULL : matched->value.buf,
-			      &matched->kvi);
+				       &matched->kvi);
-		fwrite(buf.buf, 1, buf.len, stdout);
+		if (!status)
+			fwrite(buf.buf, 1, buf.len, stdout);
 		strbuf_release(&buf);
 
 		strbuf_release(&matched->value);

builtin/receive-pack.c

@@ -177,8 +177,9 @@ static int receive_pack_config(const char *var, const char *value,
 
 		if (git_config_pathname(&path, var, value))
 			return -1;
-		strbuf_addf(&fsck_msg_types, "%cskiplist=%s",
+		if (path)
-			fsck_msg_types.len ? ',' : '=', path);
+			strbuf_addf(&fsck_msg_types, "%cskiplist=%s",
+				    fsck_msg_types.len ? ',' : '=', path);
 		free(path);
 		return 0;
 	}

config.c

@@ -1291,6 +1291,7 @@ int git_config_pathname(char **dest, const char *var, const char *value)
 
 	if (is_optional && is_missing_file(path)) {
 		free(path);
+		*dest = NULL;
 		return 0;
 	}
 
@@ -1953,7 +1954,7 @@ int git_configset_get_maybe_bool(struct config_set *set, const char *key, int *d
 		return 1;
 }
 
-int git_configset_get_pathname(struct config_set *set, const char *key, char **dest)
+static int git_configset_get_pathname(struct config_set *set, const char *key, char **dest)
 {
 	const char *value;
 	if (!git_configset_get_value(set, key, &value, NULL))

config.h

@@ -564,7 +564,6 @@ int git_configset_get_ulong(struct config_set *cs, const char *key, unsigned lon
 int git_configset_get_bool(struct config_set *cs, const char *key, int *dest);
 int git_configset_get_bool_or_int(struct config_set *cs, const char *key, int *is_bool, int *dest);
 int git_configset_get_maybe_bool(struct config_set *cs, const char *key, int *dest);
-int git_configset_get_pathname(struct config_set *cs, const char *key, char **dest);
 
 /**
  * Run only the discover part of the repo_config_get_*() functions

fetch-pack.c

@@ -1865,8 +1865,9 @@ int fetch_pack_fsck_config(const char *var, const char *value,
 
 		if (git_config_pathname(&path, var, value))
 			return -1;
-		strbuf_addf(msg_types, "%cskiplist=%s",
+		if (path)
-			msg_types->len ? ',' : '=', path);
+			strbuf_addf(msg_types, "%cskiplist=%s",
+				    msg_types->len ? ',' : '=', path);
 		free(path);
 		return 0;
 	}

fsck.c

@@ -1398,14 +1398,16 @@ int git_fsck_config(const char *var, const char *value,
 
 	if (strcmp(var, "fsck.skiplist") == 0) {
 		char *path;
-		struct strbuf sb = STRBUF_INIT;
 
 		if (git_config_pathname(&path, var, value))
 			return -1;
-		strbuf_addf(&sb, "skiplist=%s", path);
+		if (path) {
-		free(path);
+			struct strbuf sb = STRBUF_INIT;
-		fsck_set_msg_types(options, sb.buf);
+			strbuf_addf(&sb, "skiplist=%s", path);
-		strbuf_release(&sb);
+			free(path);
+			fsck_set_msg_types(options, sb.buf);
+			strbuf_release(&sb);
+		}
 		return 0;
 	}
 

gpg-interface.c

@@ -794,8 +794,16 @@ static int git_gpg_config(const char *var, const char *value,
 		fmtname = "ssh";
 
 	if (fmtname) {
+		char *program;
+		int status;
+
 		fmt = get_format_by_name(fmtname);
-		return git_config_pathname((char **) &fmt->program, var, value);
+		status = git_config_pathname(&program, var, value);
+		if (status)
+			return status;
+		if (program)
+			fmt->program = program;
+		return status;
 	}
 
 	return 0;

setup.c

@@ -1248,7 +1248,7 @@ static int safe_directory_cb(const char *key, const char *value,
 	} else {
 		char *allowed = NULL;
 
-		if (!git_config_pathname(&allowed, key, value)) {
+		if (!git_config_pathname(&allowed, key, value) && allowed) {
 			char *normalized = NULL;
 
 			/*

t/meson.build

@@ -185,6 +185,7 @@ integration_tests = [
   't1308-config-set.sh',
   't1309-early-config.sh',
   't1310-config-default.sh',
+  't1311-config-optional.sh',
   't1350-config-hooks-path.sh',
   't1400-update-ref.sh',
   't1401-symbolic-ref.sh',

t/t1311-config-optional.sh

@@ -0,0 +1,38 @@
+#!/bin/sh
+#
+# Copyright (c) 2025 Google LLC
+#
+
+test_description=':(optional) paths'
+
+. ./test-lib.sh
+
+test_expect_success 'var=:(optional)path-exists' '
+	test_config a.path ":(optional)path-exists" &&
+	>path-exists &&
+	echo path-exists >expect &&
+
+	git config get --path a.path >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success 'missing optional value is ignored' '
+	test_config a.path ":(optional)no-such-path" &&
+	# Using --show-scope ensures we skip writing not only the value
+	# but also any meta-information about the ignored key.
+	test_must_fail git config get --show-scope --path a.path >actual &&
+	test_line_count = 0 actual
+'
+
+test_expect_success 'missing optional value is ignored in multi-value config' '
+	test_when_finished "git config unset --all a.path" &&
+	git config set --append a.path ":(optional)path-exists" &&
+	git config set --append a.path ":(optional)no-such-path" &&
+	>path-exists &&
+	echo path-exists >expect &&
+
+	git config --get --path a.path >actual &&
+	test_cmp expect actual
+'
+
+test_done