git-worktrees

Git worktrees

1. Reach for a worktree only when the current checkout must stay put. The user is mid-edit, the tree is dirty, or a long build is running and the task needs a different branch. A clean idle tree does not need one: git stash or a plain git checkout is simpler.
2. List before creating. git worktree list first; pick a path and branch that are not already taken.
3. Create with an explicit branch. New branch: git worktree add <path> -b <branch>. Existing branch: git worktree add <path> <branch>. A branch checked out in one worktree cannot be checked out in another: fatal: '<branch>' is already used by worktree at '<path>'. Pick a new branch name instead of forcing it.
4. Put the worktree where the sandbox can write and git will not sweep it. Inside the repo under a gitignored path (<repo>/target/wt/<name>) or in /tmp. A sibling directory outside the repo fails the filesystem write policy, and an untracked directory inside the repo pollutes git status and git add sweeps. Verify the path is actually ignored with git check-ignore -q <path>; if it is not, add it to .git/info/exclude rather than editing the user's .gitignore.
5. Know what is shared. Commits and branches are shared through the one object store: a commit made in the worktree is immediately visible from the main checkout. HEAD, the index, and untracked files are per-worktree. Build artifacts (target/, node_modules/) are not shared either: the first build in a fresh worktree is a full cold build. Budget for it and say so if it will be slow.
6. Run checks inside the worktree. cd <path> first, then the project's own verbs (make test, cargo test -p <crate>). Running them from the main repo tests the wrong tree.
7. Remove with git, not with rm. git worktree remove <path> when the work is done. It refuses a dirty tree: contains modified or untracked files, use --force to delete it. Reset or clean the tree first, or use --force only when losing the changes is the agreed outcome. rm -rf by hand leaves a prunable entry; repair with git worktree prune -v.
8. The branch outlives the worktree. Removing the worktree keeps its branch. Delete it too when the work was abandoned (git branch -D counts as destructive: say what is being deleted and why).
9. Never mv a worktree directory. It breaks the gitdir link. Use git worktree move <path> <new-path>.
10. Leave no worktrees behind. A worktree created for one task is removed in the same session once its check ran, unless the user asked to keep it. git worktree list at the end of the task proves the cleanup.