devtools: add automatic source vars.env

Change-Id: Id885ef33bcd5fae35d8d2244e4c73b74c593ad66
Reviewed-on: https://go-review.googlesource.com/c/pkgsite-metrics/+/793080
Auto-Submit: Ethan Lee <ethanalee@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>

devtools/deploy.sh

diff --git a/devtools/deploy.sh b/devtools/deploy.sh
index e7b15ba..b5c4c23 100755
--- a/devtools/deploy.sh
+++ b/devtools/deploy.sh
@@ -10,6 +10,10 @@
 
 source devtools/lib.sh || { echo "Are you at repo root?"; exit 1; }
 
+if [[ -z "$GO_ECOSYSTEM_DEPLOY_GROUPS" && -f vars.env ]]; then
+  source vars.env
+fi
+
 usage() {
   die "usage: $0 [-n] (dev | prod) BIGQUERY_DATASET [TAG]"
 }
@@ -42,6 +46,9 @@
   local deploy_tag=${tag:-$commit}
 
   if which grants > /dev/null; then
+    if [[ -z "$GO_ECOSYSTEM_DEPLOY_GROUPS" ]]; then
+      die "GO_ECOSYSTEM_DEPLOY_GROUPS is not set. Did you source vars.env?"
+    fi
     local allowed=false
     while read _ _ ok _; do
       if [[ $ok = OK ]]; then