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

[Kazuki Yamaguchi <k@rhe.jp>]

On Thu, Apr 07, 2016 at 05:20:10PM -0400, Eric Sunshine wrote:
> On Sun, Mar 27, 2016 at 10:37 AM, Kazuki Yamaguchi <k@rhe.jp> wrote:
> > 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);
> 
> 'err' has not been populated at this point, so I suspect that this
> error message is likely to be rather uninformative.

Yes, unable_to_lock_message() is missing. Thank you for pointing it out.

> 
> > +               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;
> > +}
> > +