v2, 6 partsRewrite `git_config()` using config-set API

diff --git a/config.c b/config.c
index 0d799e0..06257d9 100644
--- a/config.c
+++ b/config.c
@@ -244,6 +244,7 @@ static int get_next_char(void)
 		cf->linenr++;
 	if (c == EOF) {
 		cf->eof = 1;
+		cf->linenr++;
 		c = '\n';
 	}
 	return c;
@@ -319,6 +320,7 @@ static int get_value(config_fn_t fn, void *data, struct strbuf *name)
 {
 	int c;
 	char *value;
+	int ret;
 
 	/* Get the full name */
 	for (;;) {
@@ -341,7 +343,15 @@ static int get_value(config_fn_t fn, void *data, struct strbuf *name)
 		if (!value)
 			return -1;
 	}
-	return fn(name->buf, value, data);
+	/*
+	 * We already consumed the \n, but we need linenr to point to
+	 * the line we just parsed during the call to fn to get
+	 * accurate line number in error messages.
+	 */
+	cf->linenr--;
+	ret = fn(name->buf, value, data);
+	cf->linenr++;
+	return ret;
 }
 
 static int get_extended_base_var(struct strbuf *name, int c)

diff --git a/config.c b/config.c
index 06257d9..110f9a5 100644
--- a/config.c
+++ b/config.c
@@ -1232,6 +1232,11 @@ int git_config_with_options(config_fn_t fn, void *data,
 	return ret;
 }
 
+struct key_value_info {
+	const char *filename;
+	int linenr;
+};
+
 int git_config(config_fn_t fn, void *data)
 {
 	return git_config_with_options(fn, data, NULL, 1);
@@ -1262,6 +1267,9 @@ static struct config_set_element *configset_find_element(struct config_set *cs,
 static int configset_add_value(struct config_set *cs, const char *key, const char *value)
 {
 	struct config_set_element *e;
+	struct string_list_item *si;
+	struct key_value_info *kv_info = xmalloc(sizeof(*kv_info));
+
 	e = configset_find_element(cs, key);
 	/*
 	 * Since the keys are being fed by git_config*() callback mechanism, they
@@ -1274,7 +1282,16 @@ static int configset_add_value(struct config_set *cs, const char *key, const cha
 		string_list_init(&e->value_list, 1);
 		hashmap_add(&cs->config_hash, e);
 	}
-	string_list_append_nodup(&e->value_list, value ? xstrdup(value) : NULL);
+	si = string_list_append_nodup(&e->value_list, value ? xstrdup(value) : NULL);
+	if (cf) {
+		kv_info->filename = strintern(cf->name);
+		kv_info->linenr = cf->linenr;
+	} else {
+		/* for values read from `git_config_from_parameters()` */
+		kv_info->filename = strintern("parameter");
+		kv_info->linenr = 0;
+	}
+	si->util = kv_info;
 
 	return 0;
 }

cache.h, config.c

diff --git a/cache.h b/cache.h
index 7292aef..11ded5a 100644
--- a/cache.h
+++ b/cache.h
@@ -8,6 +8,7 @@
 #include "gettext.h"
 #include "convert.h"
 #include "trace.h"
+#include "string-list.h"
 
 #include SHA1_HEADER
 #ifndef git_SHA_CTX
@@ -1351,9 +1352,33 @@ extern int parse_config_key(const char *var,
 			    const char **subsection, int *subsection_len,
 			    const char **key);
 
+struct config_set_element {
+	struct hashmap_entry ent;
+	char *key;
+	struct string_list value_list;
+};
+
+struct configset_list_item {
+	struct config_set_element *e;
+	int value_index;
+};
+
+/*
+ * the contents of the list are ordered according to their
+ * position in the config files and order of parsing the files.
+ * (i.e. key-value pair at the last position of .git/config will
+ * be at the last item of the list)
+ */
+
+struct configset_list {
+	struct configset_list_item *items;
+	unsigned int nr, alloc;
+};
+
 struct config_set {
 	struct hashmap config_hash;
 	int hash_initialized;
+	struct configset_list list;
 };
 
 extern void git_configset_init(struct config_set *cs);
diff --git a/config.c b/config.c
index 110f9a5..aa5c0ad 100644
--- a/config.c
+++ b/config.c
@@ -35,12 +35,6 @@ struct config_source {
 	long (*do_ftell)(struct config_source *c);
 };
 
-struct config_set_element {
-	struct hashmap_entry ent;
-	char *key;
-	struct string_list value_list;
-};
-
 static struct config_source *cf;
 
 static int zlib_compression_seen;
@@ -1237,11 +1231,44 @@ struct key_value_info {
 	int linenr;
 };
 
-int git_config(config_fn_t fn, void *data)
+static int git_config_raw(config_fn_t fn, void *data)
 {
 	return git_config_with_options(fn, data, NULL, 1);
 }
 
+static int configset_iter(struct config_set *cs, config_fn_t fn, void *data)
+{
+	int i, value_index;
+	struct string_list *values;
+	struct config_set_element *entry;
+	struct configset_list *list = &cs->list;
+	struct key_value_info *kv_info;
+
+	for (i = 0; i < list->nr; i++) {
+		entry = list->items[i].e;
+		value_index = list->items[i].value_index;
+		values = &entry->value_list;
+		if (fn(entry->key, values->items[value_index].string, data) < 0) {
+			kv_info = values->items[value_index].util;
+			if (!kv_info->linenr)
+				die("unable to parse command-line config");
+			else
+				die("bad config file line %d in %s",
+					kv_info->linenr,
+					kv_info->filename);
+		}
+	}
+	return 0;
+}
+
+static void git_config_check_init(void);
+
+int git_config(config_fn_t fn, void *data)
+{
+	git_config_check_init();
+	return configset_iter(&the_config_set, fn, data);
+}
+
 static struct config_set_element *configset_find_element(struct config_set *cs, const char *key)
 {
 	struct config_set_element k;
@@ -1268,6 +1295,7 @@ static int configset_add_value(struct config_set *cs, const char *key, const cha
 {
 	struct config_set_element *e;
 	struct string_list_item *si;
+	struct configset_list_item *l_item;
 	struct key_value_info *kv_info = xmalloc(sizeof(*kv_info));
 
 	e = configset_find_element(cs, key);
@@ -1283,6 +1311,13 @@ static int configset_add_value(struct config_set *cs, const char *key, const cha
 		hashmap_add(&cs->config_hash, e);
 	}
 	si = string_list_append_nodup(&e->value_list, value ? xstrdup(value) : NULL);
+
+	if (cs->list.nr + 1 > cs->list.alloc)
+		ALLOC_GROW(cs->list.items, cs->list.nr + 20, cs->list.alloc);
+	l_item = &cs->list.items[cs->list.nr++];
+	l_item->e = e;
+	l_item->value_index = e->value_list.nr - 1;
+
 	if (cf) {
 		kv_info->filename = strintern(cf->name);
 		kv_info->linenr = cf->linenr;
@@ -1306,6 +1341,9 @@ void git_configset_init(struct config_set *cs)
 {
 	hashmap_init(&cs->config_hash, (hashmap_cmp_fn)config_set_element_cmp, 0);
 	cs->hash_initialized = 1;
+	cs->list.nr = 0;
+	cs->list.alloc = 0;
+	cs->list.items = NULL;
 }
 
 void git_configset_clear(struct config_set *cs)
@@ -1318,10 +1356,14 @@ void git_configset_clear(struct config_set *cs)
 	hashmap_iter_init(&cs->config_hash, &iter);
 	while ((entry = hashmap_iter_next(&iter))) {
 		free(entry->key);
-		string_list_clear(&entry->value_list, 0);
+		string_list_clear(&entry->value_list, 1);
 	}
 	hashmap_free(&cs->config_hash, 1);
 	cs->hash_initialized = 0;
+	free(cs->list.items);
+	cs->list.nr = 0;
+	cs->list.alloc = 0;
+	cs->list.items = NULL;
 }
 
 static int config_set_callback(const char *key, const char *value, void *cb)
@@ -1448,7 +1490,7 @@ static void git_config_check_init(void)
 	if (the_config_set.hash_initialized)
 		return;
 	git_configset_init(&the_config_set);
-	git_config(config_set_callback, &the_config_set);
+	git_config_raw(config_set_callback, &the_config_set);
 }
 
 void git_config_clear(void)

diff --git a/t/t1308-config-set.sh b/t/t1308-config-set.sh
index 7fdf840..35c6ee2 100755
--- a/t/t1308-config-set.sh
+++ b/t/t1308-config-set.sh
@@ -197,4 +197,15 @@ test_expect_success 'proper error on error in custom config files' '
 	test_cmp expect actual
 '
 
+test_expect_success 'check line errors for malformed values' '
+	mv .git/config .git/config.old &&
+	test_when_finished "mv .git/config.old .git/config" &&
+	cat >.git/config <<-\EOF &&
+	[alias]
+		br
+	EOF
+	test_expect_code 128 git br 2>result &&
+	grep "fatal: bad config file line 2 in .git/config" result
+'
+
 test_done

Documentation/technical/api-config.txt, cache.h, config.c

diff --git a/Documentation/technical/api-config.txt b/Documentation/technical/api-config.txt
index 815c1ee..e7ec7cc 100644
--- a/Documentation/technical/api-config.txt
+++ b/Documentation/technical/api-config.txt
@@ -155,6 +155,11 @@ as well as retrieval for the queried variable, including:
 	Similar to `git_config_get_string`, but expands `~` or `~user` into
 	the user's home directory when found at the beginning of the path.
 
+`void git_die_config(const char *key)`::
+
+	Dies printing the line number and the file name of the highest
+	priority value for the configuration variable `key`.
+
 See test-config.c for usage examples.
 
 Value Parsing Helpers
diff --git a/cache.h b/cache.h
index 11ded5a..5c3dd88 100644
--- a/cache.h
+++ b/cache.h
@@ -1407,6 +1407,7 @@ extern int git_config_get_bool(const char *key, int *dest);
 extern int git_config_get_bool_or_int(const char *key, int *is_bool, int *dest);
 extern int git_config_get_maybe_bool(const char *key, int *dest);
 extern int git_config_get_pathname(const char *key, const char **dest);
+extern void git_die_config(const char *key);
 
 extern int committer_ident_sufficiently_given(void);
 extern int author_ident_sufficiently_given(void);
diff --git a/config.c b/config.c
index aa5c0ad..1e49ae7 100644
--- a/config.c
+++ b/config.c
@@ -1403,11 +1403,12 @@ const struct string_list *git_configset_get_value_multi(struct config_set *cs, c
 
 int git_configset_get_string_const(struct config_set *cs, const char *key, const char **dest)
 {
-	const char *value;
-	if (!git_configset_get_value(cs, key, &value))
-		return git_config_string(dest, key, value);
-	else
-		return 1;
+	int ret;
+	char *value;
+	ret = git_configset_get_string(cs, key, &value);
+	if (ret <= 0)
+		*dest = (const char*)value;
+	return ret;
 }
 
 int git_configset_get_string(struct config_set *cs, const char *key, char **dest)
@@ -1418,8 +1419,7 @@ int git_configset_get_string(struct config_set *cs, const char *key, char **dest
 			return config_error_nonbool(key);
 		*dest = xstrdup(value);
 		return 0;
-	}
-	else
+	} else
 		return 1;
 }
 
@@ -1514,14 +1514,22 @@ const struct string_list *git_config_get_value_multi(const char *key)
 
 int git_config_get_string_const(const char *key, const char **dest)
 {
+	int ret;
 	git_config_check_init();
-	return git_configset_get_string_const(&the_config_set, key, dest);
+	ret = git_configset_get_string_const(&the_config_set, key, dest);
+	if (ret < 0)
+		git_die_config(key);
+	return ret;
 }
 
 int git_config_get_string(const char *key, char **dest)
 {
+	int ret;
 	git_config_check_init();
-	return git_configset_get_string(&the_config_set, key, dest);
+	ret = git_configset_get_string(&the_config_set, key, dest);
+	if (ret < 0)
+		git_die_config(key);
+	return ret;
 }
 
 int git_config_get_int(const char *key, int *dest)
@@ -1556,8 +1564,24 @@ int git_config_get_maybe_bool(const char *key, int *dest)
 
 int git_config_get_pathname(const char *key, const char **dest)
 {
+	int ret;
 	git_config_check_init();
-	return git_configset_get_pathname(&the_config_set, key, dest);
+	ret = git_configset_get_pathname(&the_config_set, key, dest);
+	if (ret < 0)
+		git_die_config(key);
+	return ret;
+}
+
+void git_die_config(const char *key)
+{
+	const struct string_list *values;
+	struct key_value_info *kv_info;
+	values = git_config_get_value_multi(key);
+	kv_info = values->items[values->nr - 1].util;
+	if (!kv_info->linenr)
+		die("unable to parse command-line config");
+	else
+		die("bad config file line %d in %s",kv_info->linenr, kv_info->filename);
 }
 
 /*

t/t1308-config-set.sh, test-config.c

diff --git a/t/t1308-config-set.sh b/t/t1308-config-set.sh
index 35c6ee2..d7cdc6e 100755
--- a/t/t1308-config-set.sh
+++ b/t/t1308-config-set.sh
@@ -119,6 +119,15 @@ test_expect_success 'find integer value for a key' '
 	check_config get_int lamb.chop 65
 '
 
+test_expect_success 'find string value for a key' '
+	check_config get_string case.baz hask
+'
+
+test_expect_success 'check line error when NULL string is queried' '
+	test_expect_code 128 test-config get_string case.foo 2>result &&
+	grep "fatal: bad config file line 7 in .git/config" result
+'
+
 test_expect_success 'find integer if value is non parse-able' '
 	check_config expect_code 128 get_int lamb.head
 '
diff --git a/test-config.c b/test-config.c
index 9dd1b22..6a77552 100644
--- a/test-config.c
+++ b/test-config.c
@@ -16,6 +16,8 @@
  *
  * get_bool -> print bool value for the entered key or die
  *
+ * get_string -> print string value for the entered key or die
+ *
  * configset_get_value -> returns value with the highest priority for the entered key
  * 			from a config_set constructed from files entered as arguments.
  *
@@ -84,6 +86,14 @@ int main(int argc, char **argv)
 			printf("Value not found for \"%s\"\n", argv[2]);
 			goto exit1;
 		}
+	} else if (argc == 3 && !strcmp(argv[1], "get_string")) {
+		if (!git_config_get_string_const(argv[2], &v)) {
+			printf("%s\n", v);
+			goto exit0;
+		} else {
+			printf("Value not found for \"%s\"\n", argv[2]);
+			goto exit1;
+		}
 	} else if (!strcmp(argv[1], "configset_get_value")) {
 		for (i = 3; i < argc; i++) {
 			int err;