From a598a672484a10fd176026b488acc9dd695c844f Mon Sep 17 00:00:00 2001
From: Djun Kim <djun.m.kim@gmail.com>
Date: Thu, 3 Oct 2019 13:02:14 -0700
Subject: [PATCH] Get PR base branch from context

---
 src/main.ts | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/src/main.ts b/src/main.ts
index 1433f6b9a..2c8594047 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -14,6 +14,15 @@ async function run() {
       return;
     }
 
+    const prBase = getPrBase();
+    if (!prBase) {
+      console.log('Could not get pull request base branch from context, exiting');
+      return;
+    }
+    else {
+      core.debug(`Base branch is #${prBase}`);
+    }
+
     const client = new github.GitHub(token);
 
     core.debug(`fetching changed files for pr #${prNumber}`);
@@ -49,6 +58,15 @@ function getPrNumber(): number | undefined {
   return pullRequest.number;
 }
 
+function getPrBase(): string[] | undefined {
+  const pullRequest = github.context.payload.pull_request;
+  if (!pullRequest) {
+    return undefined;
+  }
+
+  return pullRequest.base.ref;
+}
+
 async function getChangedFiles(
   client: github.GitHub,
   prNumber: number