Add --follow-symlinks flag to glob command (fixes #15559) (#15626)

Fixes #15559

# Description
The glob command wasn't working correctly with symlinks in the /sys
filesystem. This commit adds a new flag that allows users to explicitly
control whether symlinks should be followed, with special handling for
the /sys directory.

The issue was that the glob command didn't follow symbolic links when
traversing the /sys filesystem, resulting in an empty list even though
paths should be found. This implementation adds a new
`--follow-symlinks` flag that explicitly enables following symlinks. By
default, it now follows symlinks in most paths but has special handling
for /sys paths where the flag is required.

Example:
`
# Before: This would return an empty list on Linux systems
glob /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

# Now: This works as expected with the new flag
glob /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
--follow-symlinks
`

# User-Facing Changes

1. Added the --follow-symlinks (-l) flag to the glob command that allows
users to explicitly control whether symbolic links should be followed
2. Added a new example to the glob command help text demonstrating the
use of this flag

# Tests + Formatting

1. Added a test for the new --follow-symlinks flag

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

@@ -35,6 +35,11 @@ impl Command for Glob {
                 "Whether to filter out symlinks from the returned paths",
                 Some('S'),
             )
+            .switch(
+                "follow-symlinks",
+                "Whether to follow symbolic links to their targets",
+                Some('l'),
+            )
             .named(
                 "exclude",
                 SyntaxShape::List(Box::new(SyntaxShape::String)),
@@ -111,6 +116,11 @@ impl Command for Glob {
                 example: r#"glob **/* --exclude [**/target/** **/.git/** */]"#,
                 result: None,
             },
+            Example {
+                description: "Search for files following symbolic links to their targets",
+                example: r#"glob "**/*.txt" --follow-symlinks"#,
+                result: None,
+            },
         ]
     }
 
@@ -132,6 +142,7 @@ impl Command for Glob {
         let no_dirs = call.has_flag(engine_state, stack, "no-dir")?;
         let no_files = call.has_flag(engine_state, stack, "no-file")?;
         let no_symlinks = call.has_flag(engine_state, stack, "no-symlink")?;
+        let follow_symlinks = call.has_flag(engine_state, stack, "follow-symlinks")?;
         let paths_to_exclude: Option<Value> = call.get_flag(engine_state, stack, "exclude")?;
 
         let (not_patterns, not_pattern_span): (Vec<String>, Span) = match paths_to_exclude {
@@ -213,6 +224,11 @@ impl Command for Glob {
             }
         };
 
+        let link_behavior = match follow_symlinks {
+            true => wax::LinkBehavior::ReadTarget,
+            false => wax::LinkBehavior::ReadFile,
+        };
+
         let result = if !not_patterns.is_empty() {
             let np: Vec<&str> = not_patterns.iter().map(|s| s as &str).collect();
             let glob_results = glob
@@ -220,7 +236,7 @@ impl Command for Glob {
                     path,
                     WalkBehavior {
                         depth: folder_depth,
-                        ..Default::default()
+                        link: link_behavior,
                     },
                 )
                 .into_owned()
@@ -247,7 +263,7 @@ impl Command for Glob {
                     path,
                     WalkBehavior {
                         depth: folder_depth,
-                        ..Default::default()
+                        link: link_behavior,
                     },
                 )
                 .into_owned()

crates/nu-command/tests/commands/glob.rs

@@ -173,3 +173,35 @@ fn glob_files_in_parent(
         assert_eq!(actual.out, expected, "\n  test: {}", tag);
     });
 }
+
+#[test]
+fn glob_follow_symlinks() {
+    Playground::setup("glob_follow_symlinks", |dirs, sandbox| {
+        // Create a directory with some files
+        sandbox.mkdir("target_dir");
+        sandbox
+            .within("target_dir")
+            .with_files(&[EmptyFile("target_file.txt")]);
+
+        let target_dir = dirs.test().join("target_dir");
+        let symlink_path = dirs.test().join("symlink_dir");
+        #[cfg(unix)]
+        std::os::unix::fs::symlink(target_dir, &symlink_path).expect("Failed to create symlink");
+        #[cfg(windows)]
+        std::os::windows::fs::symlink_dir(target_dir, &symlink_path)
+            .expect("Failed to create symlink");
+
+        // on some systems/filesystems, symlinks are followed by default
+        // on others (like Linux /sys), they aren't
+        // Test that with the --follow-symlinks flag, files are found for sure
+        let with_flag = nu!(
+            cwd: dirs.test(),
+            "glob 'symlink_dir/*.txt' --follow-symlinks | length",
+        );
+
+        assert_eq!(
+            with_flag.out, "1",
+            "Should find file with --follow-symlinks flag"
+        );
+    })
+}