Get head branch from PRs

index.js

@@ -39,9 +39,12 @@ Toolkit.run(async tools => {
     await tools.runInWorkspace('git', ['config', 'user.name', `"${process.env.GITHUB_USER || 'Automated Version Bump'}"`])
     await tools.runInWorkspace('git', ['config', 'user.email', `"${process.env.GITHUB_EMAIL || 'gh-action-bump-version@users.noreply.github.com'}"`])
 
-    const currentBranch = /refs\/[a-zA-Z]+\/(.*)/.exec(process.env.GITHUB_REF)[1]
+    let currentBranch = /refs\/[a-zA-Z]+\/(.*)/.exec(process.env.GITHUB_REF)[1]
+    if (process.env.GITHUB_HEAD_REF) {
+      console.log('Is pull request');
+      currentBranch = process.env.GITHUB_HEAD_REF;
+    }
     console.log('currentBranch:', currentBranch)
-
     // do it in the current checked out github branch (DETACHED HEAD)
     // important for further usage of the package.json version
     await tools.runInWorkspace('npm',