only use include on PRs, otherwise ignore

nyc.config.js

@@ -2,20 +2,32 @@
 
 const { exec } = require('child_process');
 
-console.log('Generating coverage report for changed files...');
-const files = [];
-exec('git diff --name-only HEAD~1', (err, stdout, stderr) => {
-  if (err) {
-    console.error(err + stderr);
-    return;
-  }
-  files.push(...stdout.split('\n'));
-});
-
-module.exports = {
-  include: files,
+const opts = {
   branches: 80,
   lines: 80,
   functions: 80,
   statements: 80,
 };
+
+// Only generate coverage report for changed files in PR
+// see: https://github.com/actions/checkout/issues/438#issuecomment-1446882066
+//      https://docs.github.com/en/actions/learn-github-actions/variables#default-environment-variables
+if (process.env.GITHUB_BASE_REF !== undefined) {
+  console.log('Generating coverage report for changed files...');
+  const baseRef = process.env.GITHUB_BASE_REF;
+  const headRef = process.env.GITHUB_SHA;
+  const files = [];
+  exec(
+    `git diff --name-only origin/${baseRef}..${headRef}`,
+    (err, stdout, stderr) => {
+      if (err) {
+        console.error(err + stderr);
+        return;
+      }
+      files.push(...stdout.split('\n'));
+    },
+  );
+  opts['include'] = files;
+}
+
+module.exports = opts;