Re: [PATCH v3 1/2] refs: add a new function set_worktree_head_symref

> Add a new function set_worktree_head_symref, to update HEAD symref for
> the specified worktree.
>
> To update HEAD of a linked working tree,
> create_symref("worktrees/$work_tree/HEAD", "refs/heads/$branch", msg)
> could be used. However when it comes to updating HEAD of the main
> working tree, it is unusable because it uses $GIT_DIR for
> worktree-specific symrefs (HEAD).
>
> The new function takes git_dir (real directory) as an argument, and
> updates HEAD of the working tree. This function will be used when
> renaming a branch.
>
> Signed-off-by: Kazuki Yamaguchi <k@rhe.jp>
> ---
> diff --git a/refs/files-backend.c b/refs/files-backend.c
> @@ -2894,6 +2894,41 @@ int create_symref(const char *refname, const char *target, const char *logmsg)
> +int set_worktree_head_symref(const char *gitdir, const char *target)
> +{
> +       static struct lock_file head_lock;
> +       struct ref_lock *lock;
> +       struct strbuf err = STRBUF_INIT;
> +       struct strbuf head_path = STRBUF_INIT;
> +       const char *head_rel;
> +       int ret;
> +
> +       strbuf_addf(&head_path, "%s/HEAD", absolute_path(gitdir));
> +       if (hold_lock_file_for_update(&head_lock, head_path.buf,
> +                                     LOCK_NO_DEREF) < 0) {
> +               error("%s", err.buf);

> +               strbuf_release(&err);
> +               strbuf_release(&head_path);
> +               return -1;
> +       }
> +
> +       /* head_rel will be "HEAD" for the main tree, "worktrees/wt/HEAD" for
> +          linked trees */
> +       head_rel = remove_leading_path(head_path.buf,
> +                                      absolute_path(get_git_common_dir()));
> +       /* to make use of create_symref_locked(), initialize ref_lock */
> +       lock = xcalloc(1, sizeof(struct ref_lock));
> +       lock->lk = &head_lock;
> +       lock->ref_name = xstrdup(head_rel);
> +       lock->orig_ref_name = xstrdup(head_rel);
> +
> +       ret = create_symref_locked(lock, head_rel, target, NULL);
> +
> +       unlock_ref(lock); /* will free lock */
> +       strbuf_release(&head_path);
> +       return ret;
> +}
> +