feat(cirrus): add support for prBranch (#180)

Author: bjyoungblood

services/cirrus.js

@@ -22,6 +22,7 @@ module.exports = {
       branch: isPr ? env.CIRRUS_BASE_BRANCH : env.CIRRUS_BRANCH,
       pr,
       isPr,
+      prBranch: isPr ? env.CIRRUS_BRANCH : undefined,
       slug: env.CIRRUS_REPO_FULL_NAME,
       root: env.CIRRUS_WORKING_DIR,
     };

test/services/cirrus.test.js

@@ -25,6 +25,7 @@ test('Push', (t) => {
     branch: 'master',
     pr: undefined,
     isPr: false,
+    prBranch: undefined,
     slug: 'owner/repo',
     root: '/',
   });
@@ -47,6 +48,7 @@ test('PR', (t) => {
       branch: 'master',
       pr: '239',
       isPr: true,
+      prBranch: 'pr-branch',
       slug: 'owner/repo',
       root: '/',
     }