glib-aux/trival: add code comment to nm_ref_string_equal_str()

src/libnm-glib-aux/nm-ref-string.h

@@ -136,6 +136,9 @@ nm_ref_string_equal_str(NMRefString *rstr, const char *str)
     if (!rstr)
         return FALSE;
 
+    /* We don't use streq() here, because an NMRefString might have embedded NUL characters
+     * (as the length is tracked separately). The NUL terminated C string @str must not
+     * compare equal to such a @rstr, thus we first explicitly check strlen(). */
     return rstr->len == strlen(str) && (rstr->str == str || memcmp(rstr->str, str, rstr->len) == 0);
 }