feat: added reflink support

ARCHITECTURE.md

@@ -309,10 +309,10 @@ pre_merge = ["pnpm test", "pnpm lint"]
 ### 配置约束与信任边界
 
 - **路径解析**：项目配置从 `git rev-parse --git-common-dir` 上溯到主 repo 根读取——worktree/子目录任意位置行为一致
-- **`copy_files` 路径沙箱**：拒绝 `/` 开头（绝对路径）和 `..` 段；不跟随符号链接
+- **`copy_files` 路径沙箱**：拒绝 `/` 开头（绝对路径）和 `..` 段；不跟随符号链接。复制优先使用写时复制（reflink/clonefile/DUPLICATE_EXTENTS），不支持时回退为普通拷贝
 - **hooks 安全**：hooks 通过 `sh -c`（Windows `cmd /C`）执行，无沙箱无超时——按"committed shell script"信任处理，禁运行不信任 repo
 - **hook CWD**：`pre_merge`/`post_merge` 一律 worktree 根；`post_create` 在新 worktree 内
-- **hook 环境变量**：所有 hook 注入 `WT_MAIN_REPO`（主仓库根）/`WT_WORKTREE`（worktree 路径）/`WT_BRANCH`（分支名）/`WT_BASE_BRANCH`（base 分支：new=创建来源，merge=合并目标）；叠加于继承环境。让 hook 可移植引用路径，如 `post_create = ['ln -s "$WT_MAIN_REPO/node_modules" node_modules']` 软链替代 `copy_files` 复制
+- **hook 环境变量**：所有 hook 注入 `WT_MAIN_REPO`（主仓库根）/`WT_WORKTREE`（worktree 路径）/`WT_BRANCH`（分支名）/`WT_BASE_BRANCH`（base 分支：new=创建来源，merge=合并目标）；叠加于继承环境。让 hook 可移植引用路径，如 `post_create = ['ln -s "$WT_MAIN_REPO/node_modules" node_modules']` 软链替代 `copy_files` 复制。`copy_files` 已在支持的文件系统上使用写时复制，故该软链技巧主要用于不支持 CoW 的文件系统
 - **trunk 检测**：`origin/HEAD` > `main` > `master` > 默认 `"main"`
 
 ---

Cargo.toml

@@ -27,6 +27,7 @@ rand = "0.10"
 ignore = "0.4"
 dirs = "6.0.0"
 ureq = "3"
+reflink-copy = "0.1"
 
 [dev-dependencies]
 tempfile = "3"

README.md

@@ -177,7 +177,9 @@ post_merge = []
 
 > **`copy_files` constraints** — patterns are gitignore-style and must stay
 > inside the repo: leading `/` (absolute paths) and `..` traversal are
-> rejected. Symlinks are not followed.
+> rejected. Symlinks are not followed. Files are copied using Reflink 
+> where the filesystem supports it (e.g., BTRFS, ZFS, XFS, APFS, ReFS, etc.),
+> falling back to a plain copy otherwise.
 >
 > **Hook trust boundary** — hooks run via `sh -c` (or `cmd /C` on Windows)
 > with no sandboxing or timeout. Treat `.agent-worktree.toml` like any
@@ -197,7 +199,11 @@ post_merge = []
 > | `WT_BASE_BRANCH` | Base branch (creation source for `new`, merge target for `merge`) |
 >
 > This makes `post_create` a cheaper alternative to `copy_files` when you only
-> want to share — not duplicate — heavy directories like dependencies:
+> want to share — not duplicate — heavy directories like dependencies.
+> `copy_files` already uses copy-on-write where the filesystem supports it
+> (btrfs/XFS reflink, APFS clonefile, ReFS block cloning), so a plain
+> `copy_files = ["node_modules"]` is near-free on those filesystems; the
+> symlink trick is mainly useful on filesystems without CoW:
 >
 > ```toml
 > [hooks]

src/cli/commands/lifecycle/new.rs

@@ -202,7 +202,7 @@ fn copy_files(from: &Path, to: &Path, config: &Config) -> Result<()> {
                 }
             }
 
-            if let Err(e) = std::fs::copy(path, &dest) {
+            if let Err(e) = copy_file_reflink(path, &dest) {
                 eprintln!("Warning: failed to copy {}: {e}", rel.display());
             }
         }
@@ -211,6 +211,16 @@ fn copy_files(from: &Path, to: &Path, config: &Config) -> Result<()> {
     Ok(())
 }
 
+/// Copy `from` to `to` using copy-on-write (reflink/clonefile/DUPLICATE_EXTENTS)
+/// where the filesystem supports it, falling back to a plain content copy
+/// otherwise.
+fn copy_file_reflink(from: &Path, to: &Path) -> std::io::Result<()> {
+    if to.exists() {
+        std::fs::remove_file(to)?;
+    }
+    reflink_copy::reflink_or_copy(from, to).map(|_| ())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

tests/cmd_new.rs

@@ -250,3 +250,54 @@ fn test_nested_snap_is_rejected() {
         "stderr should explain nested rejection: {stderr}"
     );
 }
+
+#[test]
+fn test_new_copies_files_matching_copy_files_pattern() {
+    let (dir, repo, home) = setup_worktree_test_env();
+
+    std::fs::write(repo.join(".env"), "SECRET=test\n").unwrap();
+
+    std::fs::write(
+        repo.join(".agent-worktree.toml"),
+        r#"
+[general]
+copy_files = [".env"]
+"#,
+    )
+    .unwrap();
+
+    let path_file = create_path_file(dir.path());
+    let output = Command::new(wt_binary())
+        .args([
+            "new",
+            "copy-files-test",
+            "--path-file",
+            path_file.to_str().unwrap(),
+        ])
+        .current_dir(&repo)
+        .env("HOME", &home)
+        .output()
+        .expect("wt new failed");
+
+    assert!(
+        output.status.success(),
+        "wt new failed: {}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+
+    let wt_path = read_path_file(&path_file);
+    let wt_root = std::path::Path::new(wt_path.trim());
+    let copied_env = wt_root.join(".env");
+    assert!(
+        copied_env.exists(),
+        ".env was not copied into the worktree at {}",
+        copied_env.display()
+    );
+    let contents = std::fs::read_to_string(&copied_env).unwrap();
+    assert_eq!(contents, "SECRET=test\n");
+    assert_eq!(
+        std::fs::read_to_string(repo.join(".env")).unwrap(),
+        contents,
+        "source and copy should match"
+    );
+}