Revise instructions for downgrading to a previous revision

[vidrep]

​https://www.haiku-os.org/guides/daily-tasks/updating-system

The instructions to downgrade to a previous revision appear outdated - referencing old server addresses and hrev1~alpha4.

[humdinger]

If I see this right, permanent downgrading isn't possible anymore, right?

[vidrep]

Downgrading is still possible. I was able to do it using those instructions as a rough guide.

[humdinger]

So, only the repo URLs need to be changed? I was under the impression that the whole "by-hrev" thingy for the haikuports repo doesn't work any more. Can you state specifically what needs to be changed to have downgrading work again?

[humdinger]

According to Vidrep on IRC, the URL https://eu.hpkg.haiku-os.org/haiku/master/$(getarch)/r1~beta3_hrev????? works for the Haiku repo.

The HaikuPorts repo isn't "versioned" though AFAIK. Only being able to downgrade one repo but not the other may be bad in some circumstances, I imagine.

Do we need to remove the whole downgrading part from the guide?

[waddlesplash]

It won't be bad as pkgman will check dependencies correctly, so the worst that will happen is that downgrading will not be possible. So, we can leave it in.

[humdinger]

OK, I created ​PR#597.

[vidrep]

Looks like it should have been closed with this commit ​https://github.com/haiku/website/commit/352032b10cff590d523dd08022350c85a7c459ae