Append output of custom commands as comments (e.g. Infracost)

[ZIJ]

At present, the output of custom run commands (specified in digger.yml) can only be seen in Actions logs, but is not appended to comments

Desired behavior: a config option to append output of the run command into the comment

Example: digger.yml with conftest as custom run command:

projects:
- name: prod
  dir: prod
  workflow: my_custom_workflow
workflows:
  my_custom_workflow:
    plan:
      steps:
      - init
      - plan
      - run: "conftest test ./prod.json -p ../policies"
    workflow_configuration:
      on_pull_request_pushed: [digger plan]
      on_pull_request_closed: [digger unlock]
      on_commit_to_default: [digger apply]

Proposal: post_output option, like this:

...
workflows:
  my_custom_workflow:
    plan:
      steps:
      - init
      - plan
      - run:
         command: "conftest test ./prod.json -p ../policies"
         post_output: true
...

[motatoes]

Also related to #529 , API for this should be flexible enough to allow for versality of options, I especially like the option to be inspired by github actions

[ZIJ]

Request from a different user (K):

is there a way to append Infracost output to the PR? because no one is going to look into GH Actions output

[ZIJ]

Proposed implementation:

• Digger sets DIGGER_OUTPUT env var, defaulting to $RUNNER_TEMP/digger-output.log
• User can pipe outputs of their custom commands to that file, e.g. run: infracost breakdown --path=. | tee -a $DIGGER_OUTPUT
• Upon finishing each job, Digger checks whether or not the output file contains anything
• If the output file is not empty, Digger appends its content to the end of the comment as code block labeled as "additional output"