basic + fundamental: Clean up includes

Split out of #37344.

src/basic/user-util.c

@@ -1,9 +1,6 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
-#include <errno.h>
 #include <fcntl.h>
-#include <stddef.h>
-#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/file.h>
@@ -22,11 +19,9 @@
 #include "format-util.h"
 #include "lock-util.h"
 #include "log.h"
-#include "macro.h"
 #include "mkdir.h"
 #include "parse-util.h"
 #include "path-util.h"
-#include "random-util.h"
 #include "string-util.h"
 #include "strv.h"
 #include "terminal-util.h"
@@ -159,6 +154,10 @@ bool is_nologin_shell(const char *shell) {
                            "/usr/bin/true");
 }
 
+bool shell_is_placeholder(const char *shell) {
+        return isempty(shell) || is_nologin_shell(shell);
+}
+
 const char* default_root_shell_at(int rfd) {
         /* We want to use the preferred shell, i.e. DEFAULT_USER_SHELL, which usually
          * will be /bin/bash. Fall back to /bin/sh if DEFAULT_USER_SHELL is not found,