Re: Rollback problems

[ludo@gnu.org (Ludovic Courtès)]

Hello!

Andreas Enge <andreas@enge.fr> skribis:

> Am Mittwoch, 23. Januar 2013 schrieb Ludovic Courtès:
>> And what if you roll back once you’re 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 “hello” was installed.  :-)
>> WDYT?
>
> No, I disagree; when I have nothing, install hello and roll back, I should 
> be back to nothing. Some other opinions would be useful on this matter.

Hmm, OK.

Well, that’s doable, so if you or others find it less confusing this
way, it’s 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.
>> 
>> 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 
> 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’s 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’.