build(vrt): sanitize branch names (uber#2948)

* build(vrt): sanitize branch names

* Update vrt/ci.js

vrt/ci.js

@@ -23,7 +23,7 @@ const {
 } = process.env;
 
 // Derive some useful constants
-const SNAPSHOT_BRANCH = `${BUILDKITE_BRANCH}--vrt`;
+const SNAPSHOT_BRANCH = `${sanitizeBranchName(BUILDKITE_BRANCH)}--vrt`;
 const [
   ORIGINAL_REPOSITORY_OWNER,
   ORIGINAL_REPOSITORY_NAME,
@@ -346,6 +346,12 @@ function getRepositoryOwnerAndNameFromURL(url) {
   return [owner, name];
 }
 
+function sanitizeBranchName(branchName) {
+  // Colons are not permitted in git branch names and for some reason
+  // Buildkite will report the branch name as "user:branch".
+  return branchName.replace(/:/g, '-');
+}
+
 function log(message) {
   console.log(`❖ VRT: ${message}`);
 }