1 files changed, 24 insertions, 0 deletions
diff --git a/scripts/environment.js b/scripts/environment.js
new file mode 100755
index 0000000000..b071a484e7
--- /dev/null
+++ b/scripts/environment.js
@@ -0,0 +1,24 @@
+#!/usr/bin/env node
+
+// Output some `export` commands with a few extra environment variables. They'll be evaluated
+// into the build environment and available for use in later steps.
+
+const github = require('@octokit/rest')();
+const {execSync} = require('child_process');
+
+const pr = process.env['CIRCLE_PULL_REQUEST'];
+if (pr) {
+    const number = +pr.match(/\/(\d+)\/?$/)[1];
+    return github.pullRequests.get({
+        owner: 'mapbox',
+        repo: 'mapbox-gl-native',
+        number
+    }).then(({data}) => {
+        const base = data.base.ref;
+        const head = process.env['CIRCLE_SHA1'];
+        const mergeBase = execSync(`git merge-base origin/${base} ${head}`).toString().trim();
+
+        console.log(`export CIRCLE_TARGET_BRANCH=${base}`);
+        console.log(`export CIRCLE_MERGE_BASE=${mergeBase}`);
+    });
+}