parse-options: add OPT_BITOP()

This is needed for diff_opt_parse() where we do

   value = (value & ~mask) | some_more;

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

parse-options.c

@@ -109,6 +109,13 @@ static int get_value(struct parse_opt_ctx_t *p,
 			*(int *)opt->value &= ~opt->defval;
 		return 0;
 
+	case OPTION_BITOP:
+		if (unset)
+			BUG("BITOP can't have unset form");
+		*(int *)opt->value &= ~opt->extra;
+		*(int *)opt->value |= opt->defval;
+		return 0;
+
 	case OPTION_COUNTUP:
 		if (*(int *)opt->value < 0)
 			*(int *)opt->value = 0;

parse-options.h

@@ -10,6 +10,7 @@ enum parse_opt_type {
 	/* options with no arguments */
 	OPTION_BIT,
 	OPTION_NEGBIT,
+	OPTION_BITOP,
 	OPTION_COUNTUP,
 	OPTION_SET_INT,
 	OPTION_CMDMODE,
@@ -118,6 +119,7 @@ struct option {
 	int flags;
 	parse_opt_cb *callback;
 	intptr_t defval;
+	intptr_t extra;
 };
 
 #define OPT_BIT_F(s, l, v, h, b, f) { OPTION_BIT, (s), (l), (v), NULL, (h), \
@@ -133,6 +135,9 @@ struct option {
 				      (h), PARSE_OPT_NOARG}
 #define OPT_GROUP(h)                { OPTION_GROUP, 0, NULL, NULL, NULL, (h) }
 #define OPT_BIT(s, l, v, h, b)      OPT_BIT_F(s, l, v, h, b, 0)
+#define OPT_BITOP(s, l, v, h, set, clear) { OPTION_BITOP, (s), (l), (v), NULL, (h), \
+					    PARSE_OPT_NOARG|PARSE_OPT_NONEG, NULL, \
+					    (set), (clear) }
 #define OPT_NEGBIT(s, l, v, h, b)   { OPTION_NEGBIT, (s), (l), (v), NULL, \
 				      (h), PARSE_OPT_NOARG, NULL, (b) }
 #define OPT_COUNTUP(s, l, v, h)     OPT_COUNTUP_F(s, l, v, h, 0)