Add --directory (-D) flag to ls, list the directory itself instead of its contents (#5970)

* Avoid extending the directory without globs in `nu_engine::glob_from`

* avoid joining a `*` to the directory without globs

* remove checks on directory permission and whether it is empty

The previous implemention of `nu_engine::glob_from` will extend the
given directory even if it containes no glob pattern. This commit
overcomes lack of consistency with the function `nu_glob::glob`.

* Add flag -D to ls, to list the directory itself instead of its contents

* add --directory (-d) flag to ls

* correct the difference between the given path and the cwd

* set default path to `.` instead of `./*` when --directory (-d) flag is true

* add comments

* add an example

* add tests

* fmt

crates/nu-command/src/filesystem/ls.rs

@@ -56,6 +56,11 @@ impl Command for Ls {
                 "Display the apparent directory size in place of the directory metadata size",
                 Some('d'),
             )
+            .switch(
+                "directory",
+                "List the specified directory itself instead of its contents",
+                Some('D'),
+            )
             .category(Category::FileSystem)
     }
 
@@ -71,6 +76,7 @@ impl Command for Ls {
         let short_names = call.has_flag("short-names");
         let full_paths = call.has_flag("full-paths");
         let du = call.has_flag("du");
+        let directory = call.has_flag("directory");
         let ctrl_c = engine_state.ctrlc.clone();
         let call_span = call.head;
         let cwd = current_dir(engine_state, stack)?;
@@ -83,7 +89,8 @@ impl Command for Ls {
                 let mut p = expand_to_real_path(p.item);
 
                 let expanded = nu_path::expand_path_with(&p, &cwd);
-                if expanded.is_dir() {
+                // Avoid checking and pushing "*" to the path when directory (do not show contents) flag is true
+                if !directory && expanded.is_dir() {
                     if permission_denied(&p) {
                         #[cfg(unix)]
                         let error_msg = format!(
@@ -116,7 +123,10 @@ impl Command for Ls {
                 (p, p_tag, absolute_path)
             }
             None => {
-                if is_empty_dir(current_dir(engine_state, stack)?) {
+                // Avoid pushing "*" to the default path when directory (do not show contents) flag is true
+                if directory {
+                    (PathBuf::from("."), call_span, false)
+                } else if is_empty_dir(current_dir(engine_state, stack)?) {
                     return Ok(Value::nothing(call_span).into_pipeline_data());
                 } else {
                     (PathBuf::from("./*"), call_span, false)
@@ -178,13 +188,30 @@ impl Command for Ls {
                         Some(path.to_string_lossy().to_string())
                     } else if let Some(prefix) = &prefix {
                         if let Ok(remainder) = path.strip_prefix(&prefix) {
-                            let new_prefix = if let Some(pfx) = diff_paths(&prefix, &cwd) {
-                                pfx
-                            } else {
-                                prefix.to_path_buf()
-                            };
+                            if directory {
+                                // When the path is the same as the cwd, path_diff should be "."
+                                let path_diff =
+                                    if let Some(path_diff_not_dot) = diff_paths(&path, &cwd) {
+                                        let path_diff_not_dot = path_diff_not_dot.to_string_lossy();
+                                        if path_diff_not_dot.is_empty() {
+                                            ".".to_string()
+                                        } else {
+                                            path_diff_not_dot.to_string()
+                                        }
+                                    } else {
+                                        path.to_string_lossy().to_string()
+                                    };
 
-                            Some(new_prefix.join(remainder).to_string_lossy().to_string())
+                                Some(path_diff)
+                            } else {
+                                let new_prefix = if let Some(pfx) = diff_paths(&prefix, &cwd) {
+                                    pfx
+                                } else {
+                                    prefix.to_path_buf()
+                                };
+
+                                Some(new_prefix.join(remainder).to_string_lossy().to_string())
+                            }
                         } else {
                             Some(path.to_string_lossy().to_string())
                         }
@@ -268,6 +295,12 @@ impl Command for Ls {
                 example: "ls -s ~ | where type == dir && modified < ((date now) - 7day)",
                 result: None,
             },
+            Example {
+                description: "List given paths, show directories themselves",
+                example:
+                    "['/path/to/directory' '/path/to/file'] | each { |it| ls -D $it } | flatten",
+                result: None,
+            },
         ]
     }
 }