Actions: Reusable workflows #98

Summary
This feature enables you to reuse an entire workflow as if it were an action. Instead of copying and pasting workflow definitions across repositories, you can reference an existing workflow with a single line of configuration.

This issue used to be called “Centrally Managed Workflow Templates.”

Intended Outcome
Use this feature to create a library of reusable workflows. This will DRY your workflow configuration, and make it easier for everyone on your team to get started with Actions. Also see Required Workflows to require these workflows for certain situations, such as deploying to production.

How will it work?
To reuse a workflow, ensure it listens to a new workflow_call event trigger, and then reference it with the familiar uses syntax. Optionally, use inputs and outputs to pass data between them, just like with actions.

For example:

name: Build & Release App

on:
  push:

jobs:
  build:
    uses: example-org/automation/workflows/build.yml@1

  release:
    needs: build
    uses: example-org/automation/workflows/release.yml@1
    with:
      artifact-url: jobs.build.outputs.artifact-url

Reusable workflows which are defined in internal repositories can be used by workflows in any repository within the same Enterprise.