parse-options: add precision handling for OPTION_BIT

Similar to 0970569 (parse-options: introduce precision handling for
`OPTION_INTEGER`, 2025-04-17) support value variables of different sizes
for OPTION_BIT.  Do that by requiring their "precision" to be set,
casting their "value" pointer accordingly and checking whether the value
fits.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: rscharfe

builtin/write-tree.c

@@ -35,6 +35,7 @@ int cmd_write_tree(int argc,
 			.type = OPTION_BIT,
 			.long_name = "ignore-cache-tree",
 			.value = &flags,
+			.precision = sizeof(flags),
 			.help = N_("only useful for debugging"),
 			.flags = PARSE_OPT_HIDDEN | PARSE_OPT_NOARG,
 			.defval = WRITE_TREE_IGNORE_CACHE_TREE,

parse-options.c

@@ -88,6 +88,14 @@ static int do_get_int_value(const void *value, size_t precision, intmax_t *ret)
 	}
 }
 
+static intmax_t get_int_value(const struct option *opt, enum opt_parsed flags)
+{
+	intmax_t ret;
+	if (do_get_int_value(opt->value, opt->precision, &ret))
+		BUG("invalid precision for option %s", optname(opt, flags));
+	return ret;
+}
+
 static enum parse_opt_result set_int_value(const struct option *opt,
 					   enum opt_parsed flags,
 					   intmax_t value)
@@ -139,11 +147,14 @@ static enum parse_opt_result do_get_value(struct parse_opt_ctx_t *p,
 		return opt->ll_callback(p, opt, NULL, unset);
 
 	case OPTION_BIT:
+	{
+		intmax_t value = get_int_value(opt, flags);
 		if (unset)
-			*(int *)opt->value &= ~opt->defval;
+			value &= ~opt->defval;
 		else
-			*(int *)opt->value |= opt->defval;
-		return 0;
+			value |= opt->defval;
+		return set_int_value(opt, flags, value);
+	}
 
 	case OPTION_NEGBIT:
 		if (unset)
@@ -631,11 +642,11 @@ static void parse_options_check(const struct option *opts)
 			optbug(opts, "OPTION_SET_INT 0 should not be negatable");
 		switch (opts->type) {
 		case OPTION_SET_INT:
+		case OPTION_BIT:
 			if (!signed_int_fits(opts->defval, opts->precision))
 				optbug(opts, "has invalid defval");
 			/* fallthru */
 		case OPTION_COUNTUP:
-		case OPTION_BIT:
 		case OPTION_NEGBIT:
 		case OPTION_NUMBER:
 		case OPTION_BITOP:

parse-options.h

@@ -172,6 +172,7 @@ struct option {
 	.short_name = (s), \
 	.long_name = (l), \
 	.value = (v), \
+	.precision = sizeof(*v), \
 	.help = (h), \
 	.flags = PARSE_OPT_NOARG|(f), \
 	.callback = NULL, \