Use GITHUB_HEAD_REF if available

.gitignore

@@ -98,3 +98,4 @@ Thumbs.db
 __tests__/runner/*
 /lib/
 /dist/
+/.idea/

package.json

@@ -9,7 +9,7 @@
     "format": "prettier --write **/*.ts",
     "format-check": "prettier --check **/*.ts",
     "lint": "eslint src/**/*.ts",
-    "package": "ncc build",
+    "package": "NODE_OPTIONS=--openssl-legacy-provider ncc build",
     "test": "jest",
     "all": "yarn build && yarn format && yarn lint && yarn package && yarn test"
   },

src/main.ts

@@ -1,7 +1,7 @@
 import { getInput, setFailed, setOutput, info } from '@actions/core';
 import { determineVersion } from './determine-version';
 import { validateHistoryDepth, checkout, createTag, refExists } from './git';
-import { getEnv } from './utils';
+import { getEnv, getEnvOrNull } from './utils';
 
 const VERSION_PLACEHOLDER = /{VERSION}/g;
 
@@ -14,7 +14,9 @@ async function run(): Promise<void> {
   info(`Previous version: ${previousVersion}`);
   setOutput('previous-version', previousVersion);
 
-  await checkout(getEnv('GITHUB_REF'));
+  const checkoutRef = getEnvOrNull('GITHUB_HEAD_REF') || getEnv('GITHUB_REF');
+
+  await checkout(checkoutRef);
 
   let currentVersion = await determineVersion();
 

src/utils.ts

@@ -1,8 +1,16 @@
-export function getEnv(name: string): string {
+export function getEnvOrNull(name: string): string | null {
   let value = process.env[name];
   if (typeof value === 'string') {
     return value;
   }
+  return null;
+}
+
+export function getEnv(name: string): string {
+  let value = getEnvOrNull(name);
+  if (typeof value === 'string') {
+    return value;
+  }
 
   throw new Error(`Missing environment variable ${name}`);
 }