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