GitLab Ensure a Branch Exists

arazzo: 1.0.1
info:
  title: GitLab Ensure a Branch Exists
  summary: Check whether a branch exists and create it from a ref only when missing.
  description: >-
    An idempotent branch provisioning flow. The workflow probes the project for
    a named branch and branches on the result: when the branch already exists it
    returns the existing branch details, and when it is missing it creates the
    branch from the supplied ref. Every step spells out its request inline so the
    flow can be read and executed without opening the underlying OpenAPI
    description.
  version: 1.0.0
sourceDescriptions:
- name: gitlabProjectsApi
  url: ../openapi/gitlab-api-v4-projects-openapi-original.yml
  type: openapi
workflows:
- workflowId: ensure-branch-exists
  summary: Create a branch only when it does not already exist.
  description: >-
    Reads a single branch by name; when it is found the flow ends with the
    existing branch, and when it is not found the flow creates the branch from
    the supplied ref.
  inputs:
    type: object
    required:
    - privateToken
    - projectId
    - branch
    - ref
    properties:
      privateToken:
        type: string
        description: GitLab Private-Token used to authenticate the API calls.
      projectId:
        type: string
        description: The ID or URL-encoded path of the project.
      branch:
        type: string
        description: The branch name to ensure exists.
      ref:
        type: string
        description: The ref (branch name or commit sha) to create the branch from.
  steps:
  - stepId: getBranch
    description: >-
      Look up the branch by name. A 200 means it already exists; a 404 means it
      must be created.
    operationId: getApiV4ProjectsIdRepositoryBranchesBranch
    parameters:
    - name: Private-Token
      in: header
      value: $inputs.privateToken
    - name: id
      in: path
      value: $inputs.projectId
    - name: branch
      in: path
      value: $inputs.branch
    successCriteria:
    - condition: $statusCode == 200 || $statusCode == 404
    outputs:
      existingBranchName: $response.body#/name
    onSuccess:
    - name: alreadyExists
      type: end
      criteria:
      - condition: $statusCode == 200
    - name: needsCreate
      type: goto
      stepId: createBranch
      criteria:
      - condition: $statusCode == 404
  - stepId: createBranch
    description: Create the missing branch from the supplied ref.
    operationId: postApiV4ProjectsIdRepositoryBranches
    parameters:
    - name: Private-Token
      in: header
      value: $inputs.privateToken
    - name: id
      in: path
      value: $inputs.projectId
    - name: branch
      in: query
      value: $inputs.branch
    - name: ref
      in: query
      value: $inputs.ref
    successCriteria:
    - condition: $statusCode == 201
    outputs:
      createdBranchName: $response.body#/name
      createdBranchUrl: $response.body#/web_url
  outputs:
    branchName: $steps.createBranch.outputs.createdBranchName