cleanup: fds::open_dir - remove mode argument

[w]open_dir does not pass O_CREAT, so the mode argument to open is never used.
also, O_CREAT | O_DIRECTORY could not be used (portably) to create a directory.
(on POSIX does not specify what should happen, on Linux it is EINVAL.)

src/builtins/cd.rs

@@ -9,7 +9,6 @@
 };
 use errno::Errno;
 use libc::{fchdir, EACCES, ELOOP, ENOENT, ENOTDIR, EPERM};
-use nix::sys::stat::Mode;
 use std::{os::fd::AsRawFd, sync::Arc};
 
 // The cd builtin. Changes the current directory to the one specified or to $HOME if none is
@@ -87,7 +86,7 @@ pub fn cd(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr]) -> Optio
 
         errno::set_errno(Errno(0));
 
-        let res = wopen_dir(&norm_dir, Mode::empty()).map_err(|err| err as i32);
+        let res = wopen_dir(&norm_dir).map_err(|err| err as i32);
 
         let res = res.and_then(|fd| {
             if unsafe { fchdir(fd.as_raw_fd()) } == 0 {

src/fds.rs

@@ -261,13 +261,13 @@ pub fn open_cloexec(path: &CStr, flags: OFlag, mode: nix::sys::stat::Mode) -> ni
 
 /// Wide character version of open_dir() that also sets the close-on-exec flag (atomically when
 /// possible).
-pub fn wopen_dir(pathname: &wstr, mode: nix::sys::stat::Mode) -> nix::Result<OwnedFd> {
-    open_dir(wcs2zstring(pathname).as_c_str(), mode)
+pub fn wopen_dir(pathname: &wstr) -> nix::Result<OwnedFd> {
+    open_dir(wcs2zstring(pathname).as_c_str())
 }
 
 /// Narrow version of wopen_dir().
-pub fn open_dir(path: &CStr, mode: nix::sys::stat::Mode) -> nix::Result<OwnedFd> {
-    open_cloexec(path, OFlag::O_RDONLY | OFlag::O_DIRECTORY, mode).map(OwnedFd::from)
+pub fn open_dir(path: &CStr) -> nix::Result<OwnedFd> {
+    open_cloexec(path, OFlag::O_RDONLY | OFlag::O_DIRECTORY, nix::sys::stat::Mode::empty()).map(OwnedFd::from)
 }
 
 /// Close a file descriptor `fd`, retrying on EINTR.

src/parser.rs

@@ -352,7 +352,7 @@ pub fn new(variables: EnvStackRef, is_principal: bool) -> ParserRef {
             global_event_blocks: AtomicU64::new(0),
         });
 
-        match open_dir(CStr::from_bytes_with_nul(b".\0").unwrap(), Mode::empty()) {
+        match open_dir(CStr::from_bytes_with_nul(b".\0").unwrap()) {
             Ok(fd) => {
                 result.libdata_mut().cwd_fd = Some(Arc::new(fd));
             }