Re: [RFC][PATCH 2/2] worktree: stop passing NULL as primary worktree

> I've cc'd Eric for a second opinion
>
> On 13/02/2026 22:29, Junio C Hamano wrote:
> > Shreyansh Paliwal <shreyanshpaliwalcmsmn@gmail.com> writes:
> >
> >> diff --git a/path.c b/path.c
> >> index d726537622..4ac86e1e58 100644
> >> --- a/path.c
> >> +++ b/path.c
> >> @@ -408,9 +408,7 @@ static void strbuf_worktree_gitdir(struct strbuf *buf,
> >>   				   const struct repository *repo,
> >>   				   const struct worktree *wt)
> >>   {
> >> -	if (!wt)
> >> -		strbuf_addstr(buf, repo->gitdir);
> >> -	else if (!wt->id)
> >> +	if (is_main_worktree(wt))
> >>   		strbuf_addstr(buf, repo->commondir);
> >>   	else
> >>   		repo_common_path_append(repo, buf, "worktrees/%s", wt->id);
> >
> > This is curious.
> >
> > We used to treat "wt==NULL" and "wt->id==NULL" differently.  Now we
> > use repo->commondir for both.  For the primary worktree, it ought to
> > be the same as repo->gitdir, so it should not matter, but makes me
> > wonder what the reason behind this difference in the original.
> >
> > We have been assuming that wt==NULL and wt->id==NULL both meant the
> > same thing: "we are talking about the primary worktree".  But the
> > code around here before this patch seems to behave differently.  Is
> > our assumption incorrect and are we making a mistake by conflating
> > these two conditions into one?
>
> My understanding is that wt==NULL means "use the current worktree" and
> wt->id==NULL means "this is the main worktree". That would explain why
> we use repo->gitdir above when wt==NULL and repo->commondir when
> wt->id==NULL, as repo->gitdir is the gitdir of the current worktree and
> repo->commondir will be the gitdir of the main worktree. If we look at
> the code in wt-status.c that's passing a NULL worktree it wants to know
> about the status of the current worktree, not the main worktree.
>
> I think that we should add a new function
>
> struct worktree *get_current_worktree(struct repository*);
>
> to worktree.c that constructs a struct worktree using repo->gitdir etc.
> The worktree id is the last path component of repo->gitdir when the
> repo->gitdir and repo->commondir differ, otherwise it is NULL. Then we
> can use that function to get the current worktree rather than passing
> NULL when we call wt_status_check_{rebase,bisect} from
> wt_status_get_state(). We should also think about whether we should
> change wt_status_get_state() to take a "struct worktree*" rather than a
> "struct repository*" instead (I've not looked at the callers to see if
> that's sensible).
>
> With that, we can gradually clean up uses of wt==NULL in the rest of the
> codebase overtime and eventually remove support for it from worktree.c
> rather than having a big flag-day patch. I don't think we need to change
> uses of wt-id==NULL.