fix: address CodeRabbit review feedback for CoW copy

- Clean up partial clone output before fallback in Darwin _fast_copy_dir
- Cache detect_os result to avoid repeated subshell calls
- Use teardown function in copy_safety tests for reliable tmpdir cleanup

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: arwtyxouymz

lib/copy.sh

@@ -79,17 +79,25 @@ merge_copy_patterns() {
 # macOS APFS: cp -cRP (clone); Linux Btrfs/XFS: cp --reflink=auto -RP
 # Callers must guard the return value with `if` or `|| true` (set -e safe).
 # Usage: _fast_copy_dir src dest
+# Cached OS value for _fast_copy_dir; set on first call.
+_fast_copy_os=""
+
 _fast_copy_dir() {
   local src="$1" dest="$2"
-  local os
-  os=$(detect_os)
+  if [ -z "$_fast_copy_os" ]; then
+    _fast_copy_os=$(detect_os)
+  fi
+  local os="$_fast_copy_os"
 
   case "$os" in
     darwin)
       # Try CoW clone first; if unsupported, fall back to regular copy
       if cp -cRP "$src" "$dest" 2>/dev/null; then
         return 0
       fi
+      # Clean up any partial clone output before fallback
+      local _clone_target="${dest%/}/$(basename "$src")"
+      [ -e "$_clone_target" ] && rm -rf "$_clone_target"
       cp -RP "$src" "$dest"
       ;;
     linux)

tests/copy_safety.bats

@@ -6,6 +6,12 @@ setup() {
   source "$PROJECT_ROOT/lib/copy.sh"
 }
 
+teardown() {
+  if [ -n "${_test_tmpdir:-}" ]; then
+    rm -rf "$_test_tmpdir"
+  fi
+}
+
 # --- _is_unsafe_path tests ---
 
 @test "absolute path is unsafe" {
@@ -87,23 +93,22 @@ setup() {
 # --- _fast_copy_dir tests ---
 
 @test "_fast_copy_dir copies directory contents" {
-  local src dst
-  src=$(mktemp -d)
-  dst=$(mktemp -d)
+  _test_tmpdir=$(mktemp -d)
+  local src="$_test_tmpdir/src" dst="$_test_tmpdir/dst"
+  mkdir -p "$src" "$dst"
   mkdir -p "$src/mydir/sub"
   echo "hello" > "$src/mydir/sub/file.txt"
 
   _fast_copy_dir "$src/mydir" "$dst/"
 
   [ -f "$dst/mydir/sub/file.txt" ]
   [ "$(cat "$dst/mydir/sub/file.txt")" = "hello" ]
-  rm -rf "$src" "$dst"
 }
 
 @test "_fast_copy_dir preserves symlinks" {
-  local src dst
-  src=$(mktemp -d)
-  dst=$(mktemp -d)
+  _test_tmpdir=$(mktemp -d)
+  local src="$_test_tmpdir/src" dst="$_test_tmpdir/dst"
+  mkdir -p "$src" "$dst"
   mkdir -p "$src/mydir"
   echo "target" > "$src/mydir/real.txt"
   ln -s real.txt "$src/mydir/link.txt"
@@ -112,12 +117,9 @@ setup() {
 
   [ -L "$dst/mydir/link.txt" ]
   [ "$(readlink "$dst/mydir/link.txt")" = "real.txt" ]
-  rm -rf "$src" "$dst"
 }
 
 @test "_fast_copy_dir fails on nonexistent source" {
-  local dst
-  dst=$(mktemp -d)
-  ! _fast_copy_dir "/nonexistent/path" "$dst/"
-  rm -rf "$dst"
+  _test_tmpdir=$(mktemp -d)
+  ! _fast_copy_dir "/nonexistent/path" "$_test_tmpdir/"
 }