Don't update api-reference docs if the only changes are the timestamps

hack/gen-swagger-doc/Dockerfile

@@ -7,6 +7,9 @@ RUN wget https://services.gradle.org/distributions/gradle-2.5-bin.zip
 RUN mkdir build/
 RUN unzip gradle-2.5-bin.zip -d build/
 
+RUN mkdir gradle-cache/
+ENV GRADLE_USER_HOME=/gradle-cache
+
 COPY build.gradle build/
 COPY gen-swagger-docs.sh build/
 
@@ -17,5 +20,7 @@ RUN wget https://raw.githubusercontent.com/kubernetes/kubernetes/master/api/swag
 RUN build/gen-swagger-docs.sh v1 https://raw.githubusercontent.com/GoogleCloudPlatform/kubernetes/master/pkg/api/v1/register.go
 RUN rm /output/*
 RUN rm /swagger-source/*
+RUN chmod -R 777 build/
+RUN chmod -R 777 gradle-cache/
 
 ENTRYPOINT ["build/gen-swagger-docs.sh"]

hack/gen-swagger-doc/gen-swagger-docs.sh

@@ -20,7 +20,7 @@ set -o errexit
 set -o nounset
 set -o pipefail
 
-cd /build/
+cd /build
 
 wget "$2" -O register.go