Parent Devfiles and workingDir vs clonePath issue

[kadel]

Currently clonePath defaults to the project name. This means that by default source code is cloned into /project/<project-name>. This is problematic for Stacks (Parent Devfiles) as they can't know where the project source code will be.

Example:

How should I set workingDir in my example devfile.yaml so It is generic enough that it can be used without everyone overriding workingDir for all commands?

# parent.yaml
schemaVersion: 2.0.0
metadata:
  name: java
components:
  - container:
      name: tools
      image: quay.io/eclipse/che-java11-maven:nightly
      mountSources: true
commands:
  - exec:
      id: mvn-package
      component: tools
      commandLine: "mvn package"
      # workingDir: ?????
      group:
        kind: build
        isDefault: true
  - exec:
      id: run
      component: tools
      commandLine: "java -jar target/*.jar"
      # workingDir: ?????
      group:
        kind: run
        isDefault: true

Now I want to use this in my local devfile.yaml

# devfile.yaml
schemaVersion: 2.0.0
metadata:
  name: myproject
projects:
  - name: myproject
      git:
        location: https://github.com/example/example
parent:
  uri: https://registry.example.com/java/parent.yaml

This won't work because commands in parent devfile don't specify workingDir so it will default to container working directory (in this case /project). But I can't set working dir in parent devfile, because I can't know what will be the project name.

[johnmcollier]

A similar issue to this is when the user brings their own project, rather than using one of the ones defined in the devfile.

If the commands in a devfile assume the working directory is $PROJECTS_ROOT/clonePath, that'll cause issues for cases like in odo, where users can use their own project/code with the devfile (and so there isn't a clear value for clonePath)

[kadel]

After a lengthy discussion, we agreed to introduce a new variable $PROJECT_SOURCE that will be expanded to a directory with project source for single project Devfiles.

In other words:
$PROJECT_SOURCE = $PROJECT_ROOT/<project_name>

TODO @kadel: add more details and update documentation