[development] Incremental upgrades

[Gabor Hojtsy]

Earnie Boyd wrote:
>> What is the purpose of this? (Not recommending to go straight to 5.1
>> when it was released, but recommending it now that 5.2 has been
>> released.) Is it a safety valve in case something upgrade-related has
>> been overlooked in the new release?
>>
>> Or does it mean that one has to follow the chain and trace back all
>> the minor releases one by one?
> 
> Good questions, I would also like to ask why upgrade.php should not 
> handle a straight 4.x to 5.2?  Isn't it designed to prevent the need to 
> do incremental upgrades so that all of the needed upgrades are self 
> contained?

Well, update.php does not include older updates, so if one has an older 
4.x site (let's say 4.5 or 4.4), he cannot upgrade directly, but first 
go to an intermediate version. I have not looked into it, but update.php 
might have problems, or would not inform the user, if he has such an old 
system that has no updates in the actual update.php/update.inc/*.install 
files code.

Previously the numbers were linear, so if you had a system updated to 
version 12, and you could only run updates from 17 through 32, then the 
missing 13-16 updates would result in a corrupted system. Now the 
numbers are not linear, there are version jumps, so telling if you miss 
updates is harder. Who knows if there were 600x updates after the 6008 
update you have done last on your site or not?

That said, it would be great to test and document from what version can 
people upgrade to a particular Drupal version, and and document that 
instead of suggesting intermediary updates for all cases.

Gabor