Tag
I reformatted 80 Scala files in one commit and a plain git blame put 207 of 260 lines in one file on it. One .git-blame-ignore-revs file brought that down to 22, on GitHub and locally.
I gave three agents a worktree each and watched what landed on disk — the pid inside the lock file, the worktree that erased itself completely, and the shared site-packages that no amount of git isolation was ever going to protect.
Switching branches is a destructive operation on your files. git worktree removes that coupling — here is the model underneath, the plumbing that makes it cheap, and the three rules Git only mentions when you break them.