Description

Worktree.Status() reports files as untracked (??) inside directories that are git worktrees (i.e., directories containing a .git file pointing to another gitdir). Real git status recognizes these .git files as worktree boundaries and does not descend into them.

Steps to reproduce

# Create a repo with a committed file
mkdir /tmp/test-repo && cd /tmp/test-repo
git init && echo "hello" > file.txt && git add . && git commit -m "init"

# Create a worktree in a subdirectory
git worktree add .worktrees/feature feature --no-track -b feature

# Real git: clean
git status --porcelain
# (no output)

# go-git: reports files inside the worktree as untracked

repo, _ := git.PlainOpen("/tmp/test-repo")
wt, _ := repo.Worktree()
st, _ := wt.Status()
fmt.Println(st.IsClean()) // false — should be true
for path, s := range st {
    fmt.Printf("%c%c %s\n", s.Staging, s.Worktree, path)
}
// Prints:
// ?? .worktrees/feature/file.txt

Expected behavior

Worktree.Status() should recognize directories containing a .git file as worktree (or submodule) boundaries and skip them during filesystem traversal, matching the behavior of git status.

Actual behavior

The filesystem walker descends into worktree directories and reports their contents as untracked files in the parent repository.

Environment

• go-git v5.16.5
• Go 1.24
• macOS / Darwin 25.2.0