config: fix typo in variable name

In git config use of the end_null variable to determine if we should be
null terminating our output.  While it is correct to say a string is
"null terminated" the character is actually the "nul" character, so this
malapropism is being fixed.

Signed-off-by: Matthew Rogers <mattr94@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/config.c

@@ -29,7 +29,7 @@ static int use_worktree_config;
 static struct git_config_source given_config_source;
 static int actions, type;
 static char *default_value;
-static int end_null;
+static int end_nul;
 static int respect_includes_opt = -1;
 static struct config_options config_options;
 static int show_origin;
@@ -151,7 +151,7 @@ static struct option builtin_config_options[] = {
 	OPT_CALLBACK_VALUE(0, "path", &type, N_("value is a path (file or directory name)"), TYPE_PATH),
 	OPT_CALLBACK_VALUE(0, "expiry-date", &type, N_("value is an expiry date"), TYPE_EXPIRY_DATE),
 	OPT_GROUP(N_("Other")),
-	OPT_BOOL('z', "null", &end_null, N_("terminate values with NUL byte")),
+	OPT_BOOL('z', "null", &end_nul, N_("terminate values with NUL byte")),
 	OPT_BOOL(0, "name-only", &omit_values, N_("show variable names only")),
 	OPT_BOOL(0, "includes", &respect_includes_opt, N_("respect include directives on lookup")),
 	OPT_BOOL(0, "show-origin", &show_origin, N_("show origin of config (file, standard input, blob, command line)")),
@@ -178,11 +178,11 @@ static void check_argc(int argc, int min, int max)
 
 static void show_config_origin(struct strbuf *buf)
 {
-	const char term = end_null ? '\0' : '\t';
+	const char term = end_nul ? '\0' : '\t';
 
 	strbuf_addstr(buf, current_config_origin_type());
 	strbuf_addch(buf, ':');
-	if (end_null)
+	if (end_nul)
 		strbuf_addstr(buf, current_config_name());
 	else
 		quote_c_style(current_config_name(), buf, NULL, 0);
@@ -678,7 +678,7 @@ int cmd_config(int argc, const char **argv, const char *prefix)
 		config_options.git_dir = get_git_dir();
 	}
 
-	if (end_null) {
+	if (end_nul) {
 		term = '\0';
 		delim = '\n';
 		key_delim = '\n';