login: drop spawn_shell CWD workaround and diagnostics

The real fix is in init (no longer leaves an initfs-scheme CWD that is
invalid in the restricted login namespace), so spawn_shell can stay
minimal again.

src/lib.rs

@@ -72,35 +72,9 @@ impl AllGroupsExt for AllGroups {
 /// spawn_shell(user).unwrap();
 /// ```
 pub fn spawn_shell<T: Default>(user: &User<T>) -> IoResult<i32> {
-    // Ensure the process has a working directory that is valid in the current
-    // (possibly restricted) login namespace before spawning the shell. After
-    // `apply_login_schemes` swaps to a namespace that only contains the schemes
-    // in DEFAULT_SCHEMES, the CWD inherited from init (e.g. `/scheme/initfs` on
-    // the live image) is no longer resolvable, and file operations that consult
-    // the CWD fd (including the child's exec) then hang. Point the CWD at the
-    // user's home (falling back to `/`), both of which live on the `file`
-    // scheme that is always present in the login namespace.
-    let chdir_ok = std::env::set_current_dir(&user.home).is_ok()
-        || std::env::set_current_dir("/").is_ok();
-    eprintln!(
-        "spawn-diag: chdir_ok={} cwd={:?}; about to spawn {:?}",
-        chdir_ok,
-        std::env::current_dir().ok(),
-        user.shell
-    );
-
     let mut command = user.shell_cmd();
 
-    let mut child = match command.spawn() {
-        Ok(c) => {
-            eprintln!("spawn-diag: command.spawn() returned Ok (child created)");
-            c
-        }
-        Err(e) => {
-            eprintln!("spawn-diag: command.spawn() FAILED: {} ({:?})", e, e.raw_os_error());
-            return Err(e);
-        }
-    };
+    let mut child = command.spawn()?;
     match child.wait()?.code() {
         Some(code) => Ok(code),
         None => Ok(1),