feat(get-merge-base): add get-merge-base helper

.github/workflows/get-merge-base.yml

@@ -0,0 +1,21 @@
+name: Get Merge Base
+
+on:
+  pull_request:
+    branches: [ main ]
+    paths:
+      - 'src/helpers/get-merge-base.ts'
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - uses: ./
+        id: merge_base
+        with:
+          helper: get-merge-base
+
+      - run: echo "Merge Base is ${{ steps.merge_base.outputs.output }}"

.gitignore

@@ -11,3 +11,4 @@ Thumbs.db
 
 node_modules
 .idea
+github-helpers.iml

README.md

@@ -184,6 +184,10 @@ Additionally, the following parameters can be used for additional control over t
 -   Returns a comma-separated list of changed files for a PR
 -   Include the regular expression parameter 'pattern' to add a filter, it will return any filepath that matches.
 
+### [get-merge-base](.github/workflows/get-merge-base.yml)
+
+-   Get merge base commit SHA for a PR
+
 ### [initiate-deployment](.github/workflows/deployments.yml#L12)
 
 -   Creates a new in-progress Github "deployment" for a commit. More information on Github deployment events can be found [here](https://docs.github.com/en/rest/reference/repos#deployments)

dist/index.js

@@ -42144,6 +42144,16 @@ var map = {
 		832,
 		913
 	],
+	"./get-merge-base": [
+		6354,
+		832,
+		354
+	],
+	"./get-merge-base.ts": [
+		6354,
+		832,
+		354
+	],
 	"./initiate-deployment": [
 		420,
 		832,

src/helpers/get-merge-base.ts

@@ -0,0 +1,26 @@
+/*
+Copyright 2023 Expedia, Inc.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    https://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import * as core from '@actions/core';
+import { context } from '@actions/github';
+import { octokit } from '../octokit';
+
+export const getMergeBase = async () => {
+  try {
+    const { data: pullRequest } = await octokit.pulls.get({ pull_number: context.issue.number, ...context.repo });
+    return pullRequest.base.sha;
+  } catch (error) {
+    core.error(`Error while fetching merge base commit SHA: ${error}`);
+  }
+  return null;
+};

test/helpers/get-merge-base.test.ts

@@ -0,0 +1,46 @@
+/*
+Copyright 2023 Expedia, Inc.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+    https://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import { Mocktokit } from '../types';
+import { octokit } from '../../src/octokit';
+import { getMergeBase } from '../../src/helpers/get-merge-base';
+
+jest.mock('@actions/core');
+jest.mock('@actions/github', () => ({
+  context: { repo: { repo: 'repo', owner: 'owner' }, issue: { number: 123 } },
+  getOctokit: jest.fn(() => ({ rest: { pulls: { get: jest.fn() } } }))
+}));
+
+describe('getMergeBase', () => {
+  it('should return merge base commit SHA', async () => {
+    (octokit.pulls.get as unknown as Mocktokit).mockImplementation(async () => ({
+      data: {
+        base: {
+          sha: 'merge_base_sha'
+        }
+      }
+    }));
+
+    const result = await getMergeBase();
+
+    expect(result).toBe('merge_base_sha');
+  });
+
+  it('should handle errors', async () => {
+    (octokit.pulls.get as unknown as jest.Mock).mockRejectedValue(new Error('API error'));
+
+    const result = await getMergeBase();
+
+    expect(result).toBeNull();
+  });
+});