use multi-stage build in Dockerfile (fixes FINERACT-771)

.dockerignore

@@ -17,3 +17,13 @@
 #
 build/*
 .gradle/*
+
+# Incremental "docker build" is faster if we can modify the Dockerfile
+# without "COPY ." re-transferring everything into the builder container.
+Dockerfile
+
+# https://github.com/containers/buildah/issues/1582
+.git/*
+.git/*/*
+.git/*/*/*
+.git/*/*/*/*

Dockerfile

@@ -15,12 +15,7 @@
 # specific language governing permissions and limitations
 # under the License.
 #
-
+FROM openjdk:8 AS builder
-FROM bitnami/tomcat:7.0.94 as fineract
-
-USER root
-RUN apt-get update -qq && apt-get install -y git openjdk-8-jdk wget
-ENV JAVA_HOME /usr/lib/jvm/java-8-openjdk-amd64/jre
 
 RUN mkdir fineract
 COPY . fineract
@@ -28,11 +23,18 @@ COPY . fineract
 WORKDIR fineract
 RUN sed -i 's/localhost/fineractmysql/' ./fineract-provider/src/main/resources/sql/migrations/list_db/V1__mifos-platform-shared-tenants.sql
 RUN ./gradlew clean war
-RUN mv build/libs/fineract-provider.war /opt/bitnami/tomcat/webapps
+
+
+FROM bitnami/tomcat:7.0.94 as fineract
+
+USER root
+RUN apt-get update -qq && apt-get install -y git openjdk-8-jdk wget
+ENV JAVA_HOME /usr/lib/jvm/java-8-openjdk-amd64/jre
+
+COPY --from=builder /fineract/build/libs/fineract-provider.war /opt/bitnami/tomcat/webapps
 
 RUN keytool -genkey -keyalg RSA -alias tomcat -keystore /opt/bitnami/tomcat/tomcat.keystore -keypass xyz123 -storepass xyz123 -noprompt -dname "CN=Fineract, OU=Fineract, O=Fineract, L=Unknown, ST=Unknown, C=Unknown"
 COPY ./docker/server.xml /opt/bitnami/tomcat/conf
 RUN chmod 664 /opt/bitnami/tomcat/conf/server.xml
 WORKDIR /opt/bitnami/tomcat/lib
 RUN wget http://central.maven.org/maven2/org/drizzle/jdbc/drizzle-jdbc/1.4/drizzle-jdbc-1.4.jar
-