chore: ensure snapshot build only builds snapshots (#58)

Author: yoshi-automation

.kokoro/release/snapshot.sh

@@ -19,6 +19,9 @@ source $(dirname "$0")/common.sh
 MAVEN_SETTINGS_FILE=$(realpath $(dirname "$0")/../../)/settings.xml
 pushd $(dirname "$0")/../../
 
+# ensure we're trying to push a snapshot (no-result returns non-zero exit code)
+grep SNAPSHOT versions.txt
+
 setup_environment_secrets
 create_settings_xml_file "settings.xml"
 
@@ -27,4 +30,4 @@ mvn clean install deploy -B \
   -DperformRelease=true \
   -Dgpg.executable=gpg \
   -Dgpg.passphrase=${GPG_PASSPHRASE} \
-  -Dgpg.homedir=${GPG_HOMEDIR}
+  -Dgpg.homedir=${GPG_HOMEDIR}

synth.metadata

@@ -1,5 +1,5 @@
 {
-  "updateTime": "2019-10-09T08:01:46.901757Z",
+  "updateTime": "2019-10-15T08:05:27.085059Z",
   "sources": [
     {
       "template": {