Re: [PATCH v2 3/3] worktree prune: improve prune logic when worktree is moved

> Automatic detection of worktree relocation by a user (via 'mv', for
> instance) was removed by 618244e160 (worktree: stop supporting moving
> worktrees manually - 2016-01-22). Prior to that,
> .git/worktrees/<tag>/gitdir was updated whenever the worktree was
> accessed in order to let the pruning logic know that the worktree was
> "active" even if it disappeared for a while (due to being located on
> removable media, for instance).

> "git worktree move" has come so we don't really need this, but since
> it's easy to do, perhaps we could keep supporting manual worktree move
> a bit longer. Notice that when a worktree is active, the "index" file
> should be updated pretty often in common case. The logic is updated to
> check for index mtime to see if the worktree is alive.
>
> The old logic of checking gitdir's mtime is dropped because nobody
> updates it anyway. The new corner case is, if the index file does not
> exist, we immediately remove the stale worktree. But if the "index"
> file does not exist, you may have a bigger problem.