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

[Eric Sunshine <sunshine@sunshineco.com>]

On Fri, Mar 2, 2018 at 10:39 PM, Nguyễn Thái Ngọc Duy <pclouds@gmail.com> wrote:
> Worktree manual move support is actually gone in 618244e160 (worktree:
> stop supporting moving worktrees manually - 2016-01-22). Before that,
> this gitdir could be updated often when the worktree is accessed. That
> keeps the worktree from being pruned by this logic.

I had a bit of trouble digesting this paragraph. Possible rewrite:

    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" is coming 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.

Seems like a reasonable approximation of the pre-618244e160 way things worked.

> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
> ---
> diff --git a/builtin/worktree.c b/builtin/worktree.c
> @@ -101,6 +101,9 @@ static int prune_worktree(const char *id, struct strbuf *reason)
>         if (!file_exists(path)) {
>                 free(path);
>                 if (st.st_mtime <= expire) {

This st.st_mtime is that of 'gitdir'...

> +                       if (!stat(git_path("worktrees/%s/index", id), &st) &&
> +                           st.st_mtime > expire)

...and this st.st_mtime is of 'index'.

I wonder if it the 'gitdir' mtime check is really that useful anymore
considering that 'index' mtime will almost certainly be more recent.

> +                               return 0;
>                         strbuf_addf(reason, _("Removing worktrees/%s: gitdir file points to non-existent location"), id);
>                         return 1;