From mboxrd@z Thu Jan  1 00:00:00 1970
From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=)
Subject: Re: Rollback problems
Date: Thu, 24 Jan 2013 12:34:25 +0100
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References: <201301232148.46744.andreas@enge.fr> <87mwvzsdzt.fsf@gnu.org>
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In-Reply-To: <201301240017.55013.andreas@enge.fr> (Andreas Enge's message of
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To: Andreas Enge <andreas@enge.fr>
Cc: bug-guix@gnu.org

Hello!

Andreas Enge <andreas@enge.fr> skribis:

> Am Mittwoch, 23. Januar 2013 schrieb Ludovic Court=C3=A8s:
>> And what if you roll back once you=E2=80=99re at the empty profile?
>
> Then nothing should happen.
>
>> It seems more intuitive for me to error out like this, because there was
>> really nothing but nothingness before =E2=80=9Chello=E2=80=9D was instal=
led.  :-)
>> WDYT?
>
> No, I disagree; when I have nothing, install hello and roll back, I shoul=
d=20
> be back to nothing. Some other opinions would be useful on this matter.

Hmm, OK.

Well, that=E2=80=99s doable, so if you or others find it less confusing this
way, it=E2=80=99s probably worth doing it.

>> This is expected (same behavior as nix-env.)  Profile generations are
>> not deleted unless you explicitly do so; this is what guarantees that
>> one can roll back anywhere they want.
>>=20
>> But I wonder if this is really worth the trouble.  In my experience, a
>> scenario like the one above rarely happens, if ever.
>
> I find the behaviour of roll back currently very confusing, and the=20
> situation looks reasonable to me:
> I install hello, it works, so I keep it.
> I install freetype, it does not work, so I drop it again.
> I install file, it does not work, so I drop it again.
> Now I expect to have only hello, but I have hello and freetype.

Right, that seems like a real-world scenario, I admit.

So I guess we can make that change.  That will mean storing the ordered
list of previous generations in each generation=E2=80=99s manifest, and then
getting the previous generation number from there.

I wonder if generations should be identified by a number at all, then.

Thoughts?

Thanks,
Ludo=E2=80=99.