Re: What's cooking in git.git (Nov 2021, #07; Mon, 29)

["Aleen 徐沛文" <pwxu@coremail.cn>]

Dears Hamano,

    In my opinion, the '--empty' should act as a strategy option like the
    'X' option to 'git-rebase'. Since that the default behaviour of not passing
    the option is stopped in the middle of an am session, should the 'die' value
    dies the whole process but not the middle state? It may also make it not
    confusing.

Aleen

> On Fri, Dec 03 2021, Elijah Newren wrote:
> 
> > On Fri, Dec 3, 2021 at 10:37 AM Ævar Arnfjörð Bjarmason
> > <avarab@gmail.com> wrote:
> >>
> >> On Wed, Dec 01 2021, Elijah Newren wrote:
> >>
> >> > On Tue, Nov 30, 2021 at 5:42 PM Aleen 徐沛文 <pwxu@coremail.cn> wrote:
> >> >>
> >> >> > Please don't, at least not this version.  There have been newer
> >> >> > submissions with three commits.
> >> >> >
> >> >> > I also still find the word 'die' confusing, since to me it suggests
> >> >> > aborting the whole am operation, and the documentation does not dispel
> >> >> > that concern.  Even if you don't like 'ask' (for consistency with
> >> >> > git-rebase), I think 'stop' or 'interrupt' would be much better
> >> >> > options than 'die'.  If you really want it to be 'die', I think the
> >> >> > behavior needs to be explained in the documentation, rather than just
> >> >> > assumed that users will understand it (because I didn't understand it
> >> >> > until I read the code).
> >> >>
> >> >> Dears Newren,
> >> >>
> >> >>     I don't think 'stop' and 'interrupt' words are better to explain more than 'die'
> >> >>     because they still indicate that it will stop or interrupt the whole am session,
> >> >>     rather than stop in the middle of it.
> >> >
> >> > Since you've been through several rounds of revisions already, if this
> >> > is the only remaining issue with your series, I wouldn't try to hold
> >> > it up for this issue; I just thought it could be fixed while you were
> >> > working on the --allow-empty stuff.
> >>
> >> FWIW I think it's worth getting the UX issue right, tweaking it is
> >> relatively easy, and if we can decide on what the thing is called
> >> then...
> >
> > :-)
> >
> >> > However, while I don't think it's worth holding up your series for
> >> > just this issue, I would definitely submit a follow-up RFC patch to
> >> > fix the wording, because I do disagree with your assertion here pretty
> >> > strongly.  Let's look at the meanings of the terms:
> >> >
> >> > die: connotes something pretty final and irreversible -- people tend
> >> > not to revive after death as far as recorded history goes; most such
> >> > recorded instances tend to be causes for people to debate the
> >> > definition of 'dead'.
> >> >
> >> > stop: could be final, but is often used in a transitory setting: "stop
> >> > and go traffic", "stopped to catch my breath",  "the train will stop
> >> > at this station", "stop! I want to get out", etc.
> >> >
> >> > interrupt: seems to nearly always be used as a transitory thing
> >> >
> >> > Now, in the computer science context, all three terms come up relative
> >> > to processes.  You can interrupt a process (the kernel does all the
> >> > time), but it'll usually continue afterwards.  Or you can give it a
> >> > SIGINT (interrupt from keyboard signal), which the process can catch
> >> > and ignore.  You can stop a process (and SIGSTOP cannot be caught),
> >> > but you can also continue it later.  die essentially means the process
> >> > is going to be gone for good (at least short of some kind of black
> >> > magic like a reversible debugger such as rr).
> >> >
> >> > So, I think it's much more likely that 'die' will be misunderstood to
> >> > mean abortion of the entire am-process, than that 'stop' or
> >> > 'interrupt' would.
> >>
> >> Why are we exposing an --empty=die at all? It's what we do by default,
> >> so why have it? The user can just not provide the "--empty" option, then
> >> they'll get the current behavior of die_user_resolve(), which seems to
> >> have inpired the name for this "die" (it exits with code 128, just like
> >> die()).
> >
> > That's an interesting angle to take; I hadn't thought of that.  It's
> > worth considering.
> >
> > We do often introduce options equivalent to the default as a way to
> > either countermand an earlier option (e.g. --do-walk overrides
> > --no-walk in git log), or because we want to allow new config options
> > that change the default while allowing the user to explicitly request
> > something different (e.g. --no-renames was introduced at the same time
> > as diff.renames), or because we may want to change the default
> > behavior and want users to be able to explicitly request a certain
> > type of behavior (e.g. rename detection is the default and
> > --no-renames overrides).
> >
> > It's not clear to me whether that type of flexibility is needed or
> > whether we can just leave it unnamed.  Three points that may affect
> > that decision: (a) the default (and actually, hardcoded) behavior
> > before this series for git-am was 'drop', (b)  the default behavior
> > for git-rebase is 'drop' (though it only affects commits which become
> > empty, something we can't determine in the context of am) and (c)
> > there was one point during the series that the author asked about just
> > removing the 'die' implementation and picking a different default.
> >
> > The above three points suggest to me that there might reasonably be
> > config added to control this or that the default could change, and
> > thus that it might be useful to name the interrupt-the-operation
> > behavior so that users can explicitly request it.  But that's
> > somewhere around three levels of chained "might" conditions, so...
> > :shrug:
> >
> >> Once we get rid of "die" the rest of the UI can follow the example of
> >> the existing "git rebase" options:
> >>
> >>     --empty={drop,keep,ask}
> >>
> >> I.e. the "drop" and "keep" will be the same, no "ask" currently, but it
> >> can be implemented in the future.
> >
> > Um, there are minor contextual differences, but what rebase calls
> > "ask" (interrupt the operation and tell the users what commands they
> > can use to keep or drop the commit and then resume the operation) _is_
> > implemented by this series -- it's just being called "die" here.
> >
> > That's the kind of maddening inconsistency in Git that users complain
> > about that I really think we should avoid adding to.  If for some
> > reason 'ask' from rebase seems like a bad choice, then I think we
> > should pick a new name for this interrupt-the-operation behavior that
> > makes sense (unlike 'die') for git-am and add it to git-rebase as a
> > preferred synonym to 'ask'.
> >
> >> Maybe I'm missing something, I haven't used "am" in this way (or rebase
> >> with --empty=*), but this just seems to me to be needlessly exposing a
> >> "die" (or "stop" or whatever) because it's how we implement this.
> >>
> >> Whereas for the UX we don't need to call it anything except the absence
> >> of an --empty option, or perhaps --no-empty.
> >
> > `--no-empty` would semantically be read by users to mean get rid of
> > empty commits, which would be a synonym of 'drop'.  I think it'd be as
> > confusing as 'die' (and maybe even more so) for naming the
> > interrupt-the-operation behavior.
> 
> Ah, I didn't look into the finer details. Yes if it does maps to "ask"
> in rebase we could just use that, so would this be consistent?:
> 
>     --empty=die -> --empty=ask
>     --empty=drop -> (ditto, no change)
>     --empty=keep -> (ditto, no change)
> 
> I think "ask" is a bit of a weird term for this, but I think consistency
> trumps a while-we're-at-it fix here.
> 
> Whatever new synonym we'd come up with (if that would be justified, that
> itself would add to confusion) could be done as a follow-up and
> implemented for both "rebase" and "am".