fix: use GITHUB_REF as documented on docs.github.com/actions (#158)

- https://docs.github.com/en/actions/learn-github-actions/events-that-trigger-workflows#pull_request_target
- https://docs.github.com/en/actions/learn-github-actions/events-that-trigger-workflows#pull_request

Author: KengoTODA

services/github.js

@@ -18,13 +18,20 @@ const getPrEvent = ({env}) => {
   return {pr: undefined, branch: undefined};
 };
 
+const getPrNumber = (env) => {
+  const event = env.GITHUB_EVENT_PATH ? require(env.GITHUB_EVENT_PATH) : undefined;
+  return event && event.pull_request ? event.pull_request.number : undefined;
+};
+
 module.exports = {
   detect({env}) {
     return Boolean(env.GITHUB_ACTIONS);
   },
   configuration({env, cwd}) {
     const isPr = env.GITHUB_EVENT_NAME === 'pull_request' || env.GITHUB_EVENT_NAME === 'pull_request_target';
-    const branch = parseBranch(env.GITHUB_REF);
+    const branch = parseBranch(
+      env.GITHUB_EVENT_NAME === 'pull_request_target' ? `refs/pull/${getPrNumber(env)}/merge` : env.GITHUB_REF
+    );
 
     return {
       name: 'GitHub Actions',

test/services/github.test.js

@@ -52,7 +52,7 @@ test('PR - with event.json file', (t) => {
       env: {
         ...env,
         GITHUB_EVENT_NAME: 'pull_request',
-        GITHUB_REF: 'refs/heads/pr-branch',
+        GITHUB_REF: 'refs/pull/10/merge',
         GITHUB_EVENT_PATH: eventFile,
       },
     }),
@@ -63,7 +63,7 @@ test('PR - with event.json file', (t) => {
       build: '1246789',
       branch: 'master',
       isPr: true,
-      prBranch: 'pr-branch',
+      prBranch: 'refs/pull/10/merge',
       pr: '10',
       root: '/workspace',
       slug: 'owner/repo',
@@ -81,7 +81,7 @@ test('PR - target', (t) => {
       env: {
         ...env,
         GITHUB_EVENT_NAME: 'pull_request_target',
-        GITHUB_REF: 'refs/heads/pr-branch',
+        GITHUB_REF: 'refs/heads/master',
         GITHUB_EVENT_PATH: eventFile,
       },
     }),
@@ -92,7 +92,7 @@ test('PR - target', (t) => {
       build: '1246789',
       branch: 'master',
       isPr: true,
-      prBranch: 'pr-branch',
+      prBranch: 'refs/pull/10/merge',
       pr: '10',
       root: '/workspace',
       slug: 'owner/repo',
@@ -110,7 +110,7 @@ test('PR - with event.json file and short branch name', (t) => {
       env: {
         ...env,
         GITHUB_EVENT_NAME: 'pull_request',
-        GITHUB_REF: 'refs/heads/pr-branch',
+        GITHUB_REF: 'refs/pull/10/merge',
         GITHUB_EVENT_PATH: eventFile,
       },
     }),
@@ -121,7 +121,7 @@ test('PR - with event.json file and short branch name', (t) => {
       build: '1246789',
       branch: 'master',
       isPr: true,
-      prBranch: 'pr-branch',
+      prBranch: 'refs/pull/10/merge',
       pr: '10',
       root: '/workspace',
       slug: 'owner/repo',
@@ -135,7 +135,7 @@ test('PR - with missing event.json file', (t) => {
       env: {
         ...env,
         GITHUB_EVENT_NAME: 'pull_request',
-        GITHUB_REF: 'refs/heads/pr-branch',
+        GITHUB_REF: 'refs/pull/10/merge',
         GITHUB_EVENT_PATH: '/tmp/null',
       },
     }),
@@ -146,7 +146,7 @@ test('PR - with missing event.json file', (t) => {
       build: '1246789',
       branch: undefined,
       isPr: true,
-      prBranch: 'pr-branch',
+      prBranch: 'refs/pull/10/merge',
       pr: undefined,
       root: '/workspace',
       slug: 'owner/repo',
@@ -157,7 +157,7 @@ test('PR - with missing event.json file', (t) => {
 test('PR - with missing event.json file path', (t) => {
   t.deepEqual(
     github.configuration({
-      env: {...env, GITHUB_EVENT_NAME: 'pull_request', GITHUB_REF: 'refs/heads/pr-branch'},
+      env: {...env, GITHUB_EVENT_NAME: 'pull_request', GITHUB_REF: 'refs/pull/10/merge'},
     }),
     {
       name: 'GitHub Actions',
@@ -166,7 +166,7 @@ test('PR - with missing event.json file path', (t) => {
       build: '1246789',
       branch: undefined,
       isPr: true,
-      prBranch: 'pr-branch',
+      prBranch: 'refs/pull/10/merge',
       pr: undefined,
       root: '/workspace',
       slug: 'owner/repo',
@@ -184,7 +184,7 @@ test('PR - with missing "pull_request" in event.json file', (t) => {
       env: {
         ...env,
         GITHUB_EVENT_NAME: 'pull_request',
-        GITHUB_REF: 'refs/heads/pr-branch',
+        GITHUB_REF: 'refs/pull/10/merge',
         GITHUB_EVENT_PATH: eventFile,
       },
     }),
@@ -195,7 +195,7 @@ test('PR - with missing "pull_request" in event.json file', (t) => {
       build: '1246789',
       branch: undefined,
       isPr: true,
-      prBranch: 'pr-branch',
+      prBranch: 'refs/pull/10/merge',
       pr: undefined,
       root: '/workspace',
       slug: 'owner/repo',
@@ -213,7 +213,7 @@ test('PR - with missing "pull_request.base" in event.json file', (t) => {
       env: {
         ...env,
         GITHUB_EVENT_NAME: 'pull_request',
-        GITHUB_REF: 'refs/heads/pr-branch',
+        GITHUB_REF: 'refs/pull/10/merge',
         GITHUB_EVENT_PATH: eventFile,
       },
     }),
@@ -224,7 +224,7 @@ test('PR - with missing "pull_request.base" in event.json file', (t) => {
       build: '1246789',
       branch: undefined,
       isPr: true,
-      prBranch: 'pr-branch',
+      prBranch: 'refs/pull/10/merge',
       pr: '10',
       root: '/workspace',
       slug: 'owner/repo',