adding merge-pr-to-branch action

.dockerignore

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+node_modules

.gitignore

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+node_modules

.prettierrc.json

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+{
+    "printWidth": 100,
+    "tabWidth": 2,
+    "useTabs": false,
+    "semi": true,
+    "singleQuote": false,
+    "trailingComma": "none",
+    "bracketSpacing": true,
+    "arrowParens": "avoid",
+    "parser": "typescript"
+  }

.vscode/settings.json

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+{
+    "[javascript]": {
+      "editor.defaultFormatter": "esbenp.prettier-vscode",
+      "editor.formatOnSave": true
+    },
+    "[javascriptreact]": {
+      "editor.defaultFormatter": "esbenp.prettier-vscode",
+      "editor.formatOnSave": true
+    },
+    "[typescript]": {
+      "editor.defaultFormatter": "esbenp.prettier-vscode",
+      "editor.formatOnSave": true
+    },
+    "[typescriptreact]": {
+      "editor.defaultFormatter": "esbenp.prettier-vscode",
+      "editor.formatOnSave": true
+    }
+}

Makefile

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+DOCKER_TAG = pr-labeled:local
+
+build:
+	docker build -t $(DOCKER_TAG) .
+
+run: build
+	docker run -t $(DOCKER_TAG)

README.md

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-# merge-pr-to-branch
+# About
+
+`merge-pr-to-branch` is a Github action that will reset the `target-branch` (defaults to `staging`) to the base branch (eg. `master`) and merge every pull request with the `deploy` label. This is triggered as defined in the Github workflow.
+
+# Getting started
+
+## Add Github Workflow
+To enable this github action, add the following workflow to your repo:
+
+`.github/workflows/merge-pr-to-branch.yml`:
+
+```yaml
+on:
+    pull_request:
+      branches:
+        - master
+      types: [labeled, unlabeled, closed, reopened]
+    push:
+      branches:
+        - master
+
+jobs:
+    build:
+      runs-on: ubuntu-latest
+      steps:
+        - uses: actions/checkout@v2
+          with:
+            ref: master
+        - uses: deliveroo/merge-pr-to-branch@v1
+```
+
+## Use the action
+
+1. To merge a pull request to the `target-branch`, add the `deploy` label. 
+2. `merge-pr-to-branch` will run and attempt to merge the pull request
+    * If successful, the `deployed` label will be added along with a comment
+    * If unsuccessful, a comment with the error will be added and the `deploy` label will be removed
+
+# Contributing
+
+Before commiting your change, ensure you build the distributed js file. Github Actions require bundled output in the repo.
+
+```
+npm run build
+```

__integrationtests__/githubHelpers.test.ts

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+import { createGithubClient, mergeDeployablePullRequests } from "../src/githubHelpers";
+
+describe("main", () => {
+  it("mergeDeployablePullRequests intergration test", async () => {
+    const client = createGithubClient();
+    await mergeDeployablePullRequests(client, "deliveroo", "dev-glue", "sandbox", "master");
+  }, 100000);
+});

__tests__/githubHelpers.test.ts

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+import * as githubHelpers from "../src/githubHelpers";
+
+describe("githubHelpers", () => {
+  it("getBranchFromRef returns last segment of ref", () => {
+    expect(githubHelpers.getBranchFromRef("foo/bar")).toBe("bar");
+  });
+  it("getBranchFromRef returns ref when no separators", () => {
+    expect(githubHelpers.getBranchFromRef("foo")).toBe("foo");
+  });
+  it("hasLabel returns true when exists in array of strings", () => {
+    expect(githubHelpers.hasLabel(["bar"], "bar")).toBeTruthy();
+  });
+  it("hasLabel returns true when exists in array of objects", () => {
+    expect(githubHelpers.hasLabel([{ name: "a" }], "a")).toBeTruthy();
+  });
+  it("hasLabel returns false when not exists in array of strings", () => {
+    expect(githubHelpers.hasLabel(["bar"], "foo")).toBeFalsy();
+  });
+  it("hasLabel returns false when not exists in array of objects", () => {
+    expect(githubHelpers.hasLabel([{ name: "foo" }], "a")).toBeFalsy();
+  });
+  it("getBranchRef calls getRef as expected", async () => {
+    const expectedResult = {};
+    const githubClient = {
+      git: {
+        getRef: jest.fn().mockResolvedValue(expectedResult)
+      }
+    };
+    const owner = "owner";
+    const repo = "repo";
+    const branch = "branch";
+    const result = await githubHelpers.getBranchRef(githubClient as any, owner, repo, branch);
+    expect(githubClient.git.getRef).toBeCalledTimes(1);
+    expect(githubClient.git.getRef).lastCalledWith({
+      owner,
+      repo,
+      ref: `heads/${branch}`
+    });
+    expect(result).toBe(expectedResult);
+  });
+  it("getBranchRef does not throw 404s", async () => {
+    const expectedResult = { status: 404 };
+    const githubClient = {
+      git: {
+        getRef: jest.fn().mockRejectedValue(expectedResult)
+      }
+    };
+    const owner = "owner";
+    const repo = "repo";
+    const branch = "branch";
+    const result = await githubHelpers.getBranchRef(githubClient as any, owner, repo, branch);
+    expect(githubClient.git.getRef).toBeCalledTimes(1);
+    expect(githubClient.git.getRef).lastCalledWith({
+      owner,
+      repo,
+      ref: `heads/${branch}`
+    });
+    expect(result).toEqual(expectedResult);
+  });
+});

action.yml

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+name: 'Merge PR to Branch'
+description: "Handles merging PRs with 'deploy' label to a target branch."
+author: 'Deliveroo'
+inputs:
+  target-branch:
+    description: 'The target branch to merge PRs to'
+    default: staging
+  repo-token:
+    description: 'The access token used to access github api'
+    default: ${{ github.token }}      
+runs:
+  using: 'node12'
+  main: 'dist/index.js'

jest.config.js

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+module.exports = {
+  clearMocks: true,
+  moduleFileExtensions: ['js', 'ts'],
+  testEnvironment: 'node',
+  testMatch: ['**/*.test.ts'],
+  testRunner: 'jest-circus/runner',
+  transform: {
+    '^.+\\.ts$': 'ts-jest'
+  },
+  verbose: true
+}