Substituting variables into the devfile from the CLI

[feloy]

/kind feature

Which functionality do you think we should add?

Actually, it is possible to use variable substitution on devfile, and the value of the variables comes from the devfile itself (from the .variables part).

It would be helpful to be able to pass values for variables from the CLI, without modifying the devfile.

For consistency, the same behaviour as the --env and --env-file options from docker could be used, by replacing env by var as these are not environment variables. For example:

$ odo dev --var CONTAINER_IMAGE=quay.io/myuser/myimage --var DEBUG=true --var USER
$ odo dev --var-file my-variables.var
$ cat my-variables.var
CONTAINER_IMAGE=quay.io/myuser/myimage
DEBUG=true
USER # this gets the value from the CLI current environment, if defined. If the env var is not defined, the variable is not overriden

AC:

• for both odo dev and odo deploy commands
• it should not modify devfile.yaml

Why is this needed?

It seems to be a common use case to create templates to be personalized at run time, similarly to how it is done with helm.

Initial discussion: https://kubernetes.slack.com/archives/C01D6L2NUAG/p1645604581682759

[kadel]

devfile/library#136