Test symlinks to invalid and reserved Windows targets

These are effectively special cases of dangling symlinks.

They should be treated the same as ordinary dangling symlinks, but
the error kind isn't NotFound for these, so currently they are not
created. The new tests should pass once that is fixed.

See #1420.

Author: EliahKagan

gix-worktree-state/tests/fixtures/make_dangling_symlink_to_windows_invalid.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+set -eu -o pipefail
+
+git init -q
+
+# On Windows, the target is an invalid file name.
+qmarks_oid=$(echo -n "???" | git hash-object -w --stdin)
+
+git update-index --index-info <<EOF
+120000 $qmarks_oid	dangling-qmarks-symlink
+EOF
+
+git commit -m "dangling symlinks with Windows invalid target in index"

gix-worktree-state/tests/fixtures/make_dangling_symlink_to_windows_reserved.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+set -eu -o pipefail
+
+git init -q
+
+# On Windows, the target is a reserved legacy DOS device name.
+con_oid=$(echo -n "CON" | git hash-object -w --stdin)
+
+git update-index --index-info <<EOF
+120000 $con_oid	dangling-con-symlink
+EOF
+
+git commit -m "dangling symlinks with Widnows reserved target in index"

gix-worktree-state/tests/state/checkout.rs

@@ -291,6 +291,54 @@ fn dangling_symlinks_can_be_created() -> crate::Result {
     Ok(())
 }
 
+#[test]
+fn dangling_symlink_to_windows_invalid_target_can_be_created() -> crate::Result {
+    let opts = opts_from_probe();
+    if !opts.fs.symlink {
+        eprintln!("Skipping dangling symlink test on filesystem that doesn't support it");
+        return Ok(());
+    }
+
+    let (_source_tree, destination, _index, outcome) =
+        checkout_index_in_tmp_dir(opts.clone(), "make_dangling_symlink_to_windows_invalid", None)?;
+    let worktree_files = dir_structure(&destination);
+    let worktree_files_stripped = stripped_prefix(&destination, &worktree_files);
+
+    assert_eq!(worktree_files_stripped, paths(["dangling-qmarks-symlink"]));
+    let symlink_path = &worktree_files[0];
+    assert!(symlink_path
+        .symlink_metadata()
+        .expect("dangling symlink is on disk")
+        .is_symlink());
+    assert_eq!(std::fs::read_link(symlink_path)?, Path::new("???"));
+    assert!(outcome.collisions.is_empty());
+    Ok(())
+}
+
+#[test]
+fn dangling_symlink_to_windows_reserved_target_can_be_created() -> crate::Result {
+    let opts = opts_from_probe();
+    if !opts.fs.symlink {
+        eprintln!("Skipping dangling symlink test on filesystem that doesn't support it");
+        return Ok(());
+    }
+
+    let (_source_tree, destination, _index, outcome) =
+        checkout_index_in_tmp_dir(opts.clone(), "make_dangling_symlink_to_windows_reserved", None)?;
+    let worktree_files = dir_structure(&destination);
+    let worktree_files_stripped = stripped_prefix(&destination, &worktree_files);
+
+    assert_eq!(worktree_files_stripped, paths(["dangling-con-symlink"]));
+    let symlink_path = &worktree_files[0];
+    assert!(symlink_path
+        .symlink_metadata()
+        .expect("dangling symlink is on disk")
+        .is_symlink());
+    assert_eq!(std::fs::read_link(symlink_path)?, Path::new("CON"));
+    assert!(outcome.collisions.is_empty());
+    Ok(())
+}
+
 #[test]
 fn allow_or_disallow_symlinks() -> crate::Result {
     let mut opts = opts_from_probe();