Merge branch 'jk/do-not-printf-NULL' into maint

"git config" had a codepath that tried to pass a NULL to
printf("%s"), which nobody seems to have noticed.

* jk/do-not-printf-NULL:
git_config_set_multivar_in_file: handle "unset" errors
git_config_set_multivar_in_file: all non-zero returns are errors
config: lower-case first word of error strings

diff --combined config.c
index 7ddb28754cc6592fa349b2bfa3816085c9644261,68a2f939efc8f312bf089485d0443fafe1af937c..47b2ce1d5a753f11bb1876e709e6a7324aa47e54
--- 1/config.c
--- 2/config.c
+++ b/config.c
@@@ -108,7 -108,7 +108,7 @@@ static int handle_path_include(const ch
  
        expanded = expand_user_path(path);
        if (!expanded)
-               return error("Could not expand include path '%s'", path);
+               return error("could not expand include path '%s'", path);
        path = expanded;
  
        /*
@@@ -950,7 -950,7 +950,7 @@@ static int git_default_branch_config(co
                else if (!strcmp(value, "always"))
                        autorebase = AUTOREBASE_ALWAYS;
                else
-                       return error("Malformed value for %s", var);
+                       return error("malformed value for %s", var);
                return 0;
        }
  
@@@ -976,7 -976,7 +976,7 @@@ static int git_default_push_config(cons
                else if (!strcmp(value, "current"))
                        push_default = PUSH_DEFAULT_CURRENT;
                else {
-                       error("Malformed value for %s: %s", var, value);
+                       error("malformed value for %s: %s", var, value);
                        return error("Must be one of nothing, matching, simple, "
                                     "upstream or current.");
                }
@@@ -1188,12 -1188,11 +1188,12 @@@ int git_config_system(void
        return !git_env_bool("GIT_CONFIG_NOSYSTEM", 0);
  }
  
 -int git_config_early(config_fn_t fn, void *data, const char *repo_config)
 +static int do_git_config_sequence(config_fn_t fn, void *data)
  {
        int ret = 0, found = 0;
        char *xdg_config = xdg_config_home("config");
        char *user_config = expand_user_path("~/.gitconfig");
 +      char *repo_config = git_pathdup("config");
  
        if (git_config_system() && !access_or_die(git_etc_gitconfig(), R_OK, 0)) {
                ret += git_config_from_file(fn, git_etc_gitconfig(),
@@@ -1229,7 -1228,6 +1229,7 @@@
  
        free(xdg_config);
        free(user_config);
 +      free(repo_config);
        return ret == 0 ? found : ret;
  }
  
@@@ -1237,6 -1235,8 +1237,6 @@@ int git_config_with_options(config_fn_
                            struct git_config_source *config_source,
                            int respect_includes)
  {
 -      char *repo_config = NULL;
 -      int ret;
        struct config_include_data inc = CONFIG_INCLUDE_INIT;
  
        if (respect_includes) {
@@@ -1257,7 -1257,11 +1257,7 @@@
        else if (config_source && config_source->blob)
                return git_config_from_blob_ref(fn, config_source->blob, data);
  
 -      repo_config = git_pathdup("config");
 -      ret = git_config_early(fn, data, repo_config);
 -      if (repo_config)
 -              free(repo_config);
 -      return ret;
 +      return do_git_config_sequence(fn, data);
  }
  
  static void git_config_raw(config_fn_t fn, void *data)
@@@ -2217,9 -2221,13 +2217,13 @@@ void git_config_set_multivar_in_file(co
                                     const char *key, const char *value,
                                     const char *value_regex, int multi_replace)
  {
-       if (git_config_set_multivar_in_file_gently(config_filename, key, value,
-                                                  value_regex, multi_replace) < 0)
-               die(_("Could not set '%s' to '%s'"), key, value);
+       if (!git_config_set_multivar_in_file_gently(config_filename, key, value,
+                                                   value_regex, multi_replace))
+               return;
+       if (value)
+               die(_("could not set '%s' to '%s'"), key, value);
+       else
+               die(_("could not unset '%s'"), key);
  }
  
  int git_config_set_multivar_gently(const char *key, const char *value,
@@@ -2400,7 -2408,7 +2404,7 @@@ int git_config_rename_section(const cha
  #undef config_error_nonbool
  int config_error_nonbool(const char *var)
  {
-       return error("Missing value for '%s'", var);
+       return error("missing value for '%s'", var);
  }
  
  int parse_config_key(const char *var,