fix: clarify unsupported directory option diagnostics

src/client/client_cli.c

@@ -187,7 +187,8 @@ static const OptionEntry* find_table_option(const char* arg) {
   return NULL;
 }
 
-static int apply_table_option(Config* config, const OptionEntry* entry, const char* value) {
+static int apply_table_option(Config* config, const OptionEntry* entry, const char* option_name,
+                              const char* value) {
   void* field = (char*)config + entry->offset;
   switch (entry->kind) {
   case OPT_FLAG:
@@ -208,8 +209,8 @@ static int apply_table_option(Config* config, const OptionEntry* entry, const ch
   }
   case OPT_UNSUPPORTED:
     log_message(LOG_LEVEL_ERROR,
-                "%s requires --dirs, which is not implemented; refusing to ignore option",
-                entry->name);
+                "%s: directory-only transfer is not implemented; refusing to ignore option",
+                option_name);
     return -1;
   }
   return -1;
@@ -221,14 +222,17 @@ int parse_args(Config* config, int argc, char* argv[], int* positional_args,
   for (int i = 1; i < argc; i++) {
     const OptionEntry* entry = find_table_option(argv[i]);
     if (entry) {
+      const char* option_name = argv[i];
+      const char* value = NULL;
       if (entry->kind != OPT_FLAG) {
-        if (i + 1 >= argc) {
+        if (entry->kind != OPT_UNSUPPORTED && i + 1 >= argc) {
           log_message(LOG_LEVEL_ERROR, "missing argument for %s", entry->name);
           return -1;
         }
-        if (apply_table_option(config, entry, argv[++i]) != 0)
-          return -1;
-      } else if (apply_table_option(config, entry, NULL) != 0) {
+        if (entry->kind != OPT_UNSUPPORTED)
+          value = argv[++i];
+      }
+      if (apply_table_option(config, entry, option_name, value) != 0) {
         return -1;
       }
       continue;

tests/test_client_cli.c

@@ -1,8 +1,10 @@
 #include "test_client_cli.h"
 #include "client_validation.h"
 #include "config.h"
+#include "log.h"
 #include "test_utils.h"
 #include "utils.h"
+#include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
@@ -260,7 +262,7 @@ static void test_parse_args_unknown_option() {
   config_delete(cfg);
 }
 
-/* Directory aliases require the not-yet-implemented --dirs behavior. */
+/* Directory aliases must report the unsupported directory-only behavior clearly. */
 static void test_parse_args_rejects_dirs_aliases() {
   static const char* const options[] = {"--dirs", "--old-dirs", "--old-d"};
 
@@ -269,8 +271,21 @@ static void test_parse_args_rejects_dirs_aliases() {
     char* argv[] = {"fastsync", (char*)options[i], "/src", "/dst"};
     int positional_args[2];
     int positional_count = 0;
+    FILE* log_file = tmpfile();
+    char log_buffer[256] = {0};
+
+    EXPECT_NOT_NULL(log_file);
+    log_set_file(log_file);
 
     EXPECT_EQ_INT(parse_args(cfg, 4, argv, positional_args, &positional_count), -1);
+    fflush(log_file);
+    rewind(log_file);
+    EXPECT_TRUE(fread(log_buffer, 1, sizeof(log_buffer) - 1, log_file) > 0);
+    EXPECT_TRUE(strstr(log_buffer, options[i]) != NULL);
+    EXPECT_TRUE(strstr(log_buffer, "directory-only transfer is not implemented") != NULL);
+    EXPECT_TRUE(strstr(log_buffer, "requires --dirs") == NULL);
+    log_set_file(NULL);
+    fclose(log_file);
     config_delete(cfg);
   }
 }