fixed docker build for Activiti/Activiti#1790

Dockerfile

@@ -3,6 +3,7 @@ FROM maven:3.5-jdk-8 as BUILDREG
 
 COPY src /usr/src/myapp/src
 COPY pom.xml /usr/src/myapp
+COPY .git .git
 RUN mvn -f /usr/src/myapp/pom.xml clean package -DskipTests
 
 FROM openjdk:alpine
@@ -14,4 +15,6 @@ ENV debug=false
 # set REMOTE_DEBUG=true to enable connections to remote debug port
 ENV REMOTE_DEBUG=false
 
+EXPOSE 8761
+
 CMD if [ "x$REMOTE_DEBUG" = "xfalse" ] ; then java $JAVA_OPTS -jar maven/*.jar ; else java $JAVA_OPTS -agentlib:jdwp=transport=dt_socket,address=8000,server=y,suspend=n -jar maven/*.jar ; fi