Subject: [PATCH v2 2/2] parseopt: check for duplicate long names and numerical options

From: René Scharfe <[email-masked]>
Date: Sat, 28 Feb 2026 10:19:16 +0100

We already check for duplicate short names.  Check for and report
duplicate long names and numerical options as well.

Perform the slightly expensive string duplicate check only when showing
the usage to keep the cost of normal invocations low.  t0012-help.sh
covers it.

Helped-by: Jeff King <[email-masked]>
Signed-off-by: René Scharfe <[email-masked]>
---
Changes since v1:
- Removed strset_contains() call.
- Only check for duplicate long names when showing the usage.

 parse-options.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/parse-options.c b/parse-options.c
index c9cafc21b9..0214c106d4 100644
--- a/parse-options.c
+++ b/parse-options.c
@@ -5,6 +5,7 @@
 #include "gettext.h"
 #include "strbuf.h"
 #include "string-list.h"
+#include "strmap.h"
 #include "utf8.h"
 
 static int disallow_abbreviated_options;
@@ -641,6 +642,7 @@ static void check_typos(const char *arg, const struct option *options)
 static void parse_options_check(const struct option *opts)
 {
 	char short_opts[128];
+	bool saw_number_option = false;
 	void *subcommand_value = NULL;
 
 	memset(short_opts, '\0', sizeof(short_opts));
@@ -655,6 +657,11 @@ static void parse_options_check(const struct option *opts)
 			else if (short_opts[opts->short_name]++)
 				optbug(opts, "short name already used");
 		}
+		if (opts->type == OPTION_NUMBER) {
+			if (saw_number_option)
+				optbug(opts, "duplicate numerical option");
+			saw_number_option = true;
+		}
 		if (opts->flags & PARSE_OPT_NODASH &&
 		    ((opts->flags & PARSE_OPT_OPTARG) ||
 		     !(opts->flags & PARSE_OPT_NOARG) ||
@@ -714,6 +721,19 @@ static void parse_options_check(const struct option *opts)
 	BUG_if_bug("invalid 'struct option'");
 }
 
+static void parse_options_check_harder(const struct option *opts)
+{
+	struct strset long_names = STRSET_INIT;
+	for (; opts->type != OPTION_END; opts++) {
+		if (opts->long_name) {
+			if (!strset_add(&long_names, opts->long_name))
+				optbug(opts, "long name already used");
+		}
+	}
+	BUG_if_bug("invalid 'struct option'");
+	strset_clear(&long_names);
+}
+
 static int has_subcommands(const struct option *options)
 {
 	for (; options->type != OPTION_END; options++)
@@ -1339,6 +1359,8 @@ static enum parse_opt_result usage_with_options_internal(struct parse_opt_ctx_t
 	const char *prefix = usage_prefix;
 	int saw_empty_line = 0;
 
+	parse_options_check_harder(opts);
+
 	if (!usagestr)
 		return PARSE_OPT_HELP;
 
-- 
2.53.0