Merge branch 'ls/config-origin'

The configuration system has been taught to phrase where it found a bad configuration variable in a better way in its error messages. "git config" learnt a new "--show-origin" option to indicate where the values come from. * ls/config-origin: config: add '--show-origin' option to print the origin of a config value config: add 'origin_type' to config_source struct rename git_config_from_buf to git_config_from_mem t: do not hide Git's exit code in tests using 'nul_to_q'