Add workspace when starting a pipeline or task

[siamaksade]

Given the workspace support in pipelines, currently one has to create a PipelineRun yaml in order to start a pipeline that requires a workspace. The tkn pipeline start command should be augmented to be able to map persistent volume claims to workspace when starting a pipeline.

Suggestion:

tkn pipeline start -w|--workspace my-workspace=my-workspace-pvc

The above syntax is similar to pipeline resources

[danielhelfand]

/kind feature

[chmouel]

maybe we can have a workspace backed by configmap if no pvc is specified?

[chmouel]

/cc @sbwsg

[ghost]

We also are discussing having an "auto" workspace just in case the user doesn't want / know how to provide one. This would be something the pipeline controller injects in response to some config and would work similarly to how pipeline resources have a PVC generated for them today (called the "artifacts pvc"), but would be more transparent to the user (hopefully).

tektoncd/pipeline#1986

[siamaksade]

Auto workspace is very useful. Still makes sense to allow users to override it but it would definitely simplify starting pipelines.

[vdemeester]

It could be something like:

• --workspace my-workspace=pvc/…
• --workspace my-workspace=emptyDir
• --workspace my-workspace=configmap/…

[khrm]

/assign khrm

[piyush-garg]

Closed by #826 and #854