Re: [RFC PATCH 4/9] sequencer: update `done_nr' when skipping commands in a todo list

From: Alban Gruin <alban.gruin@gmail.com>
To: Junio C Hamano <gitster@pobox.com>
Cc: git@vger.kernel.org,
	Johannes Schindelin <Johannes.Schindelin@gmx.de>,
	Phillip Wood <phillip.wood@dunelm.org.uk>
Subject: Re: [RFC PATCH 4/9] sequencer: update `done_nr' when skipping commands in a todo list
Date: Fri, 19 Jul 2019 20:13:44 +0200	[thread overview]
Message-ID: <1732521.CJWHkCQAay@andromeda> (raw)
In-Reply-To: <xmqqo91rxgm7.fsf@gitster-ct.c.googlers.com>

Hi,

Le 18/07/2019 à 21:55, Junio C Hamano a écrit :
> Alban Gruin <alban.gruin@gmail.com> writes:
> > In a todo list, `done_nr' is the amount of commands that were executed
> > or skipped, but skip_unnecessary_picks() did not update it.
> 
> OK.  Together with 3/9 and this one, any increment of total_nr and
> done_nr in the existing code is not removed; does it mean that
> nobody actually cares what these fields contain?  IOW, there is no
> code that says "if (list->total_nr <= i) { we are done; }" etc.?
> 
> Or are these fields used later, but somehow the lack of increment in
> the places touched by 3/9 and 4/9 is compensated?
> 

`total_nr' is not used for this, because it’s not necessarily the number of 
items in the todo list.  That’s the role of `nr'.  So the comparison is more 
like "if (list->nr <= i) { we are done; }".

Same think for `done_nr'.  Each time a command is executed, git prints 
"Rebasing ($done_nr/$total_nr)".  These two variables are written to the disk, 
and might be used by a shell prompt (eg. git-prompt.sh, oh my zsh…)

And this is actually how I found this.  Originally, I wrote what became 5/9 
and 6/9, without touching to `done_nr' and `total_nr'.  All rebase tests 
(t34??*) passed, but t9903.15 ("prompt - rebase merge") failed, because the 
value was incorrect.

The reason is that, before I changed sequencer_continue() in 6/9, it called 
another function, read_populate_todo(), which would recompute `done_nr' and 
`total_nr', then write them to the disk.  With my changes, these values would 
not have been updated after adding `exec' commands or skipping picks in 
complete_action(), so the numbers written to the disk were incorrect.

tl;dr: it does not impact how the rebase works, but it might impact the 
messages printed while rebasing or shell prompts.

> > Signed-off-by: Alban Gruin <alban.gruin@gmail.com>
> > ---
> > 
> >  sequencer.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/sequencer.c b/sequencer.c
> > index e61ae75451..ec9c3d4dc5 100644
> > --- a/sequencer.c
> > +++ b/sequencer.c
> > @@ -4939,6 +4939,7 @@ static int skip_unnecessary_picks(struct repository
> > *r,> 
> >  		MOVE_ARRAY(todo_list->items, todo_list->items + i, 
todo_list->nr - i);
> >  		todo_list->nr -= i;
> >  		todo_list->current = 0;
> > 
> > +		todo_list->done_nr += i;
> > 
> >  		if (is_fixup(peek_command(todo_list, 0)))
> >  		
> >  			record_in_rewritten(base_oid, 
peek_command(todo_list, 0));