Merge branch 'ta/config-set-1'

Use the new caching config-set API in git_config() calls.

* ta/config-set-1:
  add tests for `git_config_get_string_const()`
  add a test for semantic errors in config files
  rewrite git_config() to use the config-set API
  config: add `git_die_config()` to the config-set API
  change `git_config()` return value to void
  add line number and file name info to `config_set`
  config.c: fix accuracy of line number in errors
  config.c: mark error and warnings strings for translation

Documentation/technical/api-config.txt

@@ -155,6 +155,19 @@ 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.
 
+`git_die_config(const char *key, const char *err, ...)`::
+
+	First prints the error message specified by the caller in `err` and then
+	dies printing the line number and the file name of the highest priority
+	value for the configuration variable `key`.
+
+`void git_die_config_linenr(const char *key, const char *filename, int linenr)`::
+
+	Helper function which formats the die error message according to the
+	parameters entered. Used by `git_die_config()`. It can be used by callers
+	handling `git_config_get_value_multi()` to print the correct error message
+	for the desired value.
+
 See test-config.c for usage examples.
 
 Value Parsing Helpers