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

[Phillip Wood <phillip.wood123@gmail.com>]

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.

Thanks

Phillip