builtin/apply: make parse_ignorewhitespace_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_ignorewhitespace_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

@@ -57,20 +57,20 @@ static int parse_whitespace_option(struct apply_state *state, const char *option
 	return error(_("unrecognized whitespace option '%s'"), option);
 }
 
-static void parse_ignorewhitespace_option(struct apply_state *state,
-					  const char *option)
+static int parse_ignorewhitespace_option(struct apply_state *state,
+					 const char *option)
 {
 	if (!option || !strcmp(option, "no") ||
 	    !strcmp(option, "false") || !strcmp(option, "never") ||
 	    !strcmp(option, "none")) {
 		state->ws_ignore_action = ignore_ws_none;
-		return;
+		return 0;
 	}
 	if (!strcmp(option, "change")) {
 		state->ws_ignore_action = ignore_ws_change;
-		return;
+		return 0;
 	}
-	die(_("unrecognized whitespace ignore option '%s'"), option);
+	return error(_("unrecognized whitespace ignore option '%s'"), option);
 }
 
 static void set_default_whitespace_mode(struct apply_state *state)
@@ -4629,8 +4629,8 @@ static void init_apply_state(struct apply_state *state,
 	git_apply_config();
 	if (apply_default_whitespace && parse_whitespace_option(state, apply_default_whitespace))
 		exit(1);
-	if (apply_default_ignorewhitespace)
-		parse_ignorewhitespace_option(state, apply_default_ignorewhitespace);
+	if (apply_default_ignorewhitespace && parse_ignorewhitespace_option(state, apply_default_ignorewhitespace))
+		exit(1);
 }
 
 static void clear_apply_state(struct apply_state *state)