Feature Request: Ability to specify sketch version to install.

[nickanderson]

We should be able to specify which version of a sketch to install.

Thoughts that accompany this:
sketch pinning, separation of update vs install (relates to issue #234)

[sigurdteigen]

Additionally, I don't know how this works today. But sketch version should be specified in the config/instantiation of a sketch. This is key if we want to avoid checking sketches themselves into VCS.

[nickanderson]

You made me think it might also be desirable to be able to install multiple versions of a sketch at the same time.

Can you expand on what you mean by avoiding checking sketches into VCS?

[sigurdteigen]

We could treat the sketches themselves as 'software', and install them in a local repo outside of masterfiles, e.g. /var/cfengine/sketches. And only have sketch configs in masterfiles. Would work for at least stock sketches.

[nickanderson]

That's an interesting idea. I had only thought of them as components of policy previously.

[astraverkhau]

cf-sketch update sketch:name
cf-sketch update all

might also be useful to update sketch templates.

[tzz]

Today, the first found version of a sketch from all the search locations is installed.

The upcoming changes will let you filter sketches by version in the install and search requests.

How should updating a sketch differ from uninstalling, then installing a newer version? Remember CFEngine is a policy language and parsing with cf-promises is not sufficient, so we have to be very careful not to break the whole site policy with a backwards incompatible change.

[nickanderson]

random thought: maybe the namespace should include the major/minor version number?
Would that provide a safety net for backwards incompatible sketch updates?

[tzz]

That's the plan, and I hope it will rarely be necessary--normally you can keep using the same namespace and version.

[tzz]

With the new DC API, a specific sketch version can be specified. Also any sketch can specify the minimum version of its dependencies. See howto/dc_api.md for the details.