[PATCH v6 6/7] config: add `git_die_config()` to the config-set API

[Tanay Abhra <tanayabh@gmail.com>]

Add `git_die_config` that dies printing the line number and the file name
of the highest priority value for the configuration variable `key`.

It has usage in non-callback based config value retrieval where we can
raise an error and die if there is a semantic error.
For example,

	if (!git_config_get_value(key, &value)) {
		/* NULL values not allowed */
		if (!value)
			git_config_die(key);
		else
			/* do work */
	}

Signed-off-by: Tanay Abhra <tanayabh@gmail.com>
---
 Documentation/technical/api-config.txt |  5 +++++
 cache.h                                |  1 +
 config.c                               | 27 +++++++++++++++++++++++++--
 3 files changed, 31 insertions(+), 2 deletions(-)

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 4d3c6bd..243f618 100644
--- a/cache.h
+++ b/cache.h
@@ -1406,6 +1406,7 @@ 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 6b4dd65..15fcd91 100644
--- a/config.c
+++ b/config.c
@@ -1515,8 +1515,12 @@ 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)
@@ -1557,10 +1561,29 @@ 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 '%s' from command-line config"), key);
+	else
+		die(_("bad config variable '%s' at file line %d in %s"),
+			key,
+			kv_info->linenr,
+			kv_info->filename);
+ }
+
 /*
  * Find all the stuff for git_config_set() below.
  */
-- 
1.9.0.GIT