[gentoo-dev] System stability - update.mask

[William McArthur]

The following is some thoughts on how to provide the stability that I 
think most users really want while keeping the bleeding edge ones happy. 
This was promped by the IRC discussion I posted to the list earlier today.

The problem with a stability metric on each pacakge as described in the 
channel is it doesn't describe the stability of the interaction of the 
packages between each other. It would not have solved the libpng 
problems many users had. Becuase I'm sure libpng-1.2.* is a solid 
package and each other package that linked against libpng-1.0.* would 
have had a reasonable stability metric from it's use before 
libpng-1.2.* was released.

What I think would work well is a checkpoint system where every other 
month or so we have a package freeze for about a week or less. Then what 
I call a update.mask is generated based on the newest versions of all 
working packages out there. I originally thought of checkpoints as 
milestones like the mozilla guys use but a milestone is a goal, this is 
more like a saved state in a game.

This update.mask is a lot like the package.mask in format but instead of 
disabling packages it defines a leading edge of packages that are not 
`emerge --update world` past. Kinda like drawing a line in the sand and 
saying all packages on one side of the line are reasonably tested to 
work well together. If the user wants to he can explictly emerge a 
package that is on the other side of that line but it would require him 
to type the version he wants.

Also, I think this would obsolete the "world favorites" list that is 
maintained for a system. As I understand this feature it is to prevent 
the endless recompiling of point release of dependicies.

I envision an option added to emerge that is like the `java-config 
--list-available-vms` but it would be `emerge 
--list-available-checkpoints`. The user can then select the desired 
checkpoint with something like `emerge --set-checkpoint gentoo-YYYY-MM` 
which then updated a symlink or something to the selected update.mask 
file. Also it would be nice to have a bleeding edge update.mask that 
doens't draw any leading edge.

One thing I haven't figured out is how to deal with new packages added 
after the update.mask. The update.mask wouldn't know about the new 
package and I think updating old check points should be advoided. 
Suggestions welcome.

Feed back welcomed.

Sandy McArthur