main.c: Improve relative path detection

Otherwise, the following resources would be considered valid:

- /user/../test
- /user/./test
- /user/a/.
- /user/a/./test

main.c

@@ -395,16 +395,22 @@ static bool path_isrel(const char *const path)
 {
     if (!strcmp(path, "..")
         || !strcmp(path, ".")
-        || !strcmp(path, "./")
-        || !strcmp(path, "../")
+        || !strncmp(path, "./", strlen("./"))
+        || !strncmp(path, "../", strlen("../"))
+        || strstr(path, "/./")
         || strstr(path, "/../"))
         return true;
 
-    static const char suffix[] = "/..";
-    const size_t n = strlen(path), sn = strlen(suffix);
+    static const char *const suffixes[] = {"/.", "/.."};
 
-    if (n >= sn && !strcmp(path + n - sn, suffix))
-        return true;
+    for (size_t i = 0; i < sizeof suffixes / sizeof *suffixes; i++)
+    {
+        const char *const suffix = suffixes[i];
+        const size_t n = strlen(path), sn = strlen(suffix);
+
+        if (n >= sn && !strcmp(path + n - sn, suffix))
+            return true;
+    }
 
     return false;
 }