Crate git_cow 

Git worktrees cloned from a per-repository template checkout, sharing disk blocks until written. macOS clones with cp -c (clonefile), Linux with cp --reflink=always (FICLONE)

Functions

add

Create wt by cloning template, refreshed to template_start and warmed from repo first. new_branch and commitish are git worktree add’s; on error nothing is left behind

can_clone

Whether a file in src_dir clones into dst_dir: both on one volume that supports it. Probed with one small file, since filesystem names miss mount options like XFS without reflink

git

Runs git in dir and returns its trimmed stdout

warm

Refresh an existing template with the gitignored directories of src, a checkout or a worktree whose work merged