Subject: Re: [PATCH 2/2] revision: implement --show-linear-break for --graph

From: Junio C Hamano <[email-masked]>
Date: Sun, 17 Jan 2021 18:09:44 -0800

Junio C Hamano <[email-masked]> writes:

> In other words, revs->break_revision_mark is left NULL unless
> --show-linear-break is given.
>
>> @@ -4192,8 +4192,8 @@ const char *get_revision_mark(const struct rev_info *revs, const struct commit *
>>  		else
>>  			return ">";
>>  	} else if (revs->graph) {
>> -		if (!commit->parents)
>> -			return "#";
>> +		if (revs->break_revision_mark && !commit->parents)
>> +			return revs->break_revision_mark;
>
> And that causes this to break.  Now "--graph" alone won't show '#'
> for the root commits, despite that is what [1/2] wanted to do.
>
> Here is a fix-up, plus some minimum tests.  

Having said all that, I do not mind if the new markings were
activated only when --show-linear-break option (or a separate new
option) is given.  But if that is where we want to go, your [1/2]
that uses the new markings unconditionally is a regression.

A better organization, if we wanted to have multiple and smaller
steps than a single whole thing, would be:

 [1/2] Introduce a new "--mark-root-commits" option, or abuse the
       existing "--show-linear-break" option, and change "*<>"
       marking used for commits to "#LR" (or whatever appropriate)
       when the option is in effect.  Document the behaviour and add
       tests.

 [2/2] Introduce "--show-linear-break=<custom-value>" option.
       Document the behaviour and add tests.

If you apply [1/2] and [2/2] with the earlier fixes I sent, you'll
see many fallouts from existing tests, as the representation of the
root commit is changed unconditionally.  We view breakages of tests
as a rough estimate of how badly end-user scripts could break, and
the picture was not very pretty.  And that is why I am suggesting
the above "only do the new markings when asked, not unconditionally"
approach.

I still am skeptical that spending 3 more letters to denote roots is
worth it, though.

Thanks.