Feature Request: Trigger build after pull request is closed

[catto]

What happened:
Some users deploy their apps every open pull request with ~pr trigger and the apps would be named with each pull request number.
Once a pull request is merged or closed, no one takes care of temporarily deployed apps from pull request build. Then unused/abandoned apps retain on their infrastructure.

What you expected to happen:
Screwdriver triggers a build after each pull request is closed so that users can run teardown build and keep their compute cluster clean.

For example,

jobs:
    pullrequest:
        requires: ~pr
        image: node:8
        steps:
        - test: build and test
        - deploy: <deploy app using SD_PULL_REQUEST environment variable as its name>
        - check: <test against http://endpoint-pr-$SD_PULL_REQUEST.example.com>
    pr-teardown:
        # triggers after pr is closed
        requires: ~prclosed
        image: node:8
        steps:
        - teardown: <remove endpoint-pr-$SD_PULL_REQUEST.example.com app>

[jithine]

How is this different than enabling pull request chain and user adding a job to do clean up ? Even better option will to to combine this teardown step with PR build steps and make a template

[catto]

@jithin1987 Users can deploy, test, teardown in a single event using chainPR feature. But in some cases, users don't want to teardown their instance automatically after tests.

For instance, screwdriver has homepage. Each author has to get screenshot and paste it to the PR. (screwdriver-cd/homepage#41 ).

If there is PR-closed trigger, we can achieve a workflow like below:

• When new PR is open, deploy the homepage to a temporary instance without teardown job.
• The deploy job adds a comment like "changes have been deployed to http://homepage-pr-X.example.com" to the PR.
• We can check if the changes works properly on each reviewer's browsers/environment.
• The instance will be cleaned up after PR is closed.