Re: [PATCH v4 1/2] worktrees: add find_shared_symref

> die_if_checked_out to use the same infrastructure as
> find_shared_symref.
>
> Soon, we will use find_shared_symref to protect notes merges in
> worktrees.
>
> Signed-off-by: David Turner <dturner@twopensource.com>
> ---
> diff --git a/branch.c b/branch.c
> index c85be07..9b5e3b3 100644
> --- a/branch.c
> +++ b/branch.c
> @@ -349,31 +350,47 @@ static void check_linked_checkout(const char *branch, const char *id)
>                 strbuf_addstr(&gitdir, get_git_common_dir());
>         skip_prefix(branch, "refs/heads/", &branch);
>         strbuf_strip_suffix(&gitdir, ".git");
> -       die(_("'%s' is already checked out at '%s'"), branch, gitdir.buf);
> +       return strbuf_detach(&gitdir, NULL);

>  done:
>         strbuf_release(&path);
>         strbuf_release(&sb);
>         strbuf_release(&gitdir);
> +
> +       return NULL;
>  }
>
> -void die_if_checked_out(const char *branch)
> +char *find_shared_symref(const char *symref, const char *target)
>  {
>         struct strbuf path = STRBUF_INIT;
>         DIR *dir;
>         struct dirent *d;
> +       char *existing;
>
> -       check_linked_checkout(branch, NULL);
> +       if ((existing = find_linked_symref(symref, target, NULL)))
> +               return existing;
>
>         strbuf_addf(&path, "%s/worktrees", get_git_common_dir());
>         dir = opendir(path.buf);
>         strbuf_release(&path);
>         if (!dir)
> -               return;
> +               return NULL;
>
>         while ((d = readdir(dir)) != NULL) {
>                 if (!strcmp(d->d_name, ".") || !strcmp(d->d_name, ".."))
>                         continue;
> -               check_linked_checkout(branch, d->d_name);
> +               if ((existing = find_linked_symref(symref, target, d->d_name)))
> +                       return existing;

>         }
>         closedir(dir);
> +
> +       return NULL;
> +}
> +
> +void die_if_checked_out(const char *branch)
> +{
> +       char *existing;
> +
> +       existing = find_shared_symref("HEAD", branch);
> +       if (existing)
> +               die(_("'%s' is already checked out at '%s'"), branch, existing);
>  }
> diff --git a/branch.h b/branch.h
> index 58aa45f..0f466c7 100644
> --- a/branch.h
> +++ b/branch.h
> @@ -59,4 +59,12 @@ extern int read_branch_desc(struct strbuf *, const char *branch_name);
>   */
>  extern void die_if_checked_out(const char *branch);
>
> +/*
> + * Check if a per-worktree symref points to a ref in the main worktree
> + * or any linked worktree, and return the path to the exising worktree
> + * if it is.  Returns NULL if there is no existing ref.  The caller is
> + * responsible for freeing the returned path.
> + */
> +extern char *find_shared_symref(const char *symref, const char *branch);