Re: [PATCH 2/2] rebase -i: be careful to wrap up fixup/squash chains

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Junio,

On Tue, 4 Sep 2018, Junio C Hamano wrote:

> > diff --git a/sequencer.c b/sequencer.c
> > index 84bf598c3e..ac5c805c14 100644
> > --- a/sequencer.c
> > +++ b/sequencer.c
> > @@ -3578,9 +3578,20 @@ static int commit_staged_changes(struct replay_opts *opts,
> >  		 * the commit message and if there was a squash, let the user
> >  		 * edit it.
> >  		 */
> > -		if (is_clean && !oidcmp(&head, &to_amend) &&
> > -		    opts->current_fixup_count > 0 &&
> > -		    file_exists(rebase_path_stopped_sha())) {
> > +		if (!is_clean || !opts->current_fixup_count)
> > +			; /* this is not the final fixup */
> > +		else if (oidcmp(&head, &to_amend) ||
> > +			 !file_exists(rebase_path_stopped_sha())) {
> > +			/* was a final fixup or squash done manually? */
> > +			if (!is_fixup(peek_command(todo_list, 0))) {
> > +				unlink(rebase_path_fixup_msg());
> > +				unlink(rebase_path_squash_msg());
> > +				unlink(rebase_path_current_fixups());
> > +				strbuf_reset(&opts->current_fixups);
> > +				opts->current_fixup_count = 0;
> > +			}
> 
> Let me see if the code is easily grokkable by (trying to) follow
> aloud.
> 
>     We used to refrain from going into this big else clause that
>     does the fixup-squash handling when is_clean is false,
>     current-count is not yet zero, head and to-amend are different

s/not yet zero/still zero/

>     commits or stopped-sha file is missing.  The updated code still
>     refrains from going into the big else clause under exactly the
>     same condition, but it learned to clean up the state, when the
>     _next_ one is not a fix-up, i.e. when we are looking at the last
>     fixup/squash in the current chain.  And the lack of clean-up
>     would have resulted in the next step misbehaving.

s/next step/ next fixup or squash chain, if any,/

You got the gist right.

> I see a few calls to is_fixup(peek_command()) and a local boolean
> variable final_fixup used in this function.  I have to wonder if it
> makes the resulting code, especially the above part, easier to
> follow and understand, if the function peeked todo-list to check if
> we are dealing with the final fix-up in a chain very early just
> once, and used it to see "are we doing the final fixup/squash in the
> current chain?" throughout the rest of the function.
> 
> 	Side note: I actually think that the existing final_fixup
> 	boolean means something different (iow, final_fixup is not
> 	set inside the new "clean-up" code above, even though we
> 	dealt with the last one in the fix-up chain, and that is not
> 	a bug---which means that "final_fixup" does not mean "we are
> 	dealing with the last one in the fix-up chain"), which may
> 	want to be clarified a bit with in-code comment near where
> 	the variable is defined for the function to be readable.

Indeed. The `final_fixup` name tries to convey "need to finalize the final
fixup", as in: show the commit message in an editor if any squash! commits
were included, and otherwise simply clean the commit message of all those
commented-out lines.

So that's very different from "is the previously-run todo command a final
fixup in a fixup/squash chain?"

> In any case, thanks for fixing this, which seems to have appeared in
> Git 2.18.  Let's fork a topic from maint, cook it in 'next' and aim
> for eventually merging it down for both 2.19 and 2.18 tracks.

Sounds good,
Dscho

> 
> > +		} else {
> > +			/* we are in a fixup/squash chain */
> >  			const char *p = opts->current_fixups.buf;
> >  			int len = opts->current_fixups.len;
> >  
> > diff --git a/t/t3415-rebase-autosquash.sh b/t/t3415-rebase-autosquash.sh
> > index 7d5ea340b3..13f5688135 100755
> > --- a/t/t3415-rebase-autosquash.sh
> > +++ b/t/t3415-rebase-autosquash.sh
> > @@ -330,7 +330,7 @@ test_expect_success 'wrapped original subject' '
> >  	test $base = $parent
> >  '
> >  
> > -test_expect_failure 'abort last squash' '
> > +test_expect_success 'abort last squash' '
> >  	test_when_finished "test_might_fail git rebase --abort" &&
> >  	test_when_finished "git checkout master" &&
>