builtin/apply: make parse_whitespace_option() return -1 instead of die()ing

To libify `git apply` functionality we have to signal errors to the
caller instead of die()ing.

To do that in a compatible manner with the rest of the error handling
in builtin/apply.c, parse_whitespace_option() should return -1 instead
of calling die().

Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/apply.c

@@ -27,34 +27,34 @@ static const char * const apply_usage[] = {
 	NULL
 };
 
-static void parse_whitespace_option(struct apply_state *state, const char *option)
+static int parse_whitespace_option(struct apply_state *state, const char *option)
 {
 	if (!option) {
 		state->ws_error_action = warn_on_ws_error;
-		return;
+		return 0;
 	}
 	if (!strcmp(option, "warn")) {
 		state->ws_error_action = warn_on_ws_error;
-		return;
+		return 0;
 	}
 	if (!strcmp(option, "nowarn")) {
 		state->ws_error_action = nowarn_ws_error;
-		return;
+		return 0;
 	}
 	if (!strcmp(option, "error")) {
 		state->ws_error_action = die_on_ws_error;
-		return;
+		return 0;
 	}
 	if (!strcmp(option, "error-all")) {
 		state->ws_error_action = die_on_ws_error;
 		state->squelch_whitespace_errors = 0;
-		return;
+		return 0;
 	}
 	if (!strcmp(option, "strip") || !strcmp(option, "fix")) {
 		state->ws_error_action = correct_ws_error;
-		return;
+		return 0;
 	}
-	die(_("unrecognized whitespace option '%s'"), option);
+	return error(_("unrecognized whitespace option '%s'"), option);
 }
 
 static void parse_ignorewhitespace_option(struct apply_state *state,
@@ -4589,7 +4589,8 @@ static int option_parse_whitespace(const struct option *opt,
 {
 	struct apply_state *state = opt->value;
 	state->whitespace_option = arg;
-	parse_whitespace_option(state, arg);
+	if (parse_whitespace_option(state, arg))
+		exit(1);
 	return 0;
 }
 
@@ -4626,8 +4627,8 @@ static void init_apply_state(struct apply_state *state,
 	strbuf_init(&state->root, 0);
 
 	git_apply_config();
-	if (apply_default_whitespace)
-		parse_whitespace_option(state, apply_default_whitespace);
+	if (apply_default_whitespace && parse_whitespace_option(state, apply_default_whitespace))
+		exit(1);
 	if (apply_default_ignorewhitespace)
 		parse_ignorewhitespace_option(state, apply_default_ignorewhitespace);
 }