Sensible defaults to avoid packaging disruptions during release windows

[kyle-blair]

During most release windows we run into the mismatching versions error when installing packages. If you create packages on one production org that are used in multiple other production orgs, it is very likely that one of those orgs (or one of their sandboxes used during development) are not on the same release.

In the past, there was no reasonable workaround. Now, it appears that adding the release: previous option to the package's definition file will allow package versions to be installed regardless of which release the target org is on.

The problem is that this option is only allowed during release windows. Outside of the release window, having it in a definition file results in an error when creating package versions. That means this workaround results in a manual step to add the option to every package at the beginning of the release window and remove it at the end of the window.

I propose changing the default for the release option to previous, instead of preview, so that no action is necessary unless you intend to use brand new features. I assume that there are more people impacted by the current behavior than there are people trying to use bleeding edge features, so this change to the default behavior would eliminate a lot of effort for the majority of users. Not to mention, if you're using new features, you obviously won't be able to install those packages on orgs that haven't been upgraded yet anyways.

An alternative workaround, that I find less ideal than the solution above, is for Salesforce to simply ignore the release option outside of release windows instead of throwing an error. We would still have to add that attribute to all of our definition files, but it would be a one-time effort since we could leave it there indefinitely.

I'm interested in everyone's thoughts on this. I'm surprised there isn't much discussion about it given how much impact I've seen from it.

related: #2923