TT#17642 docker: follow policy to include NGCP repository

Change-Id: Iaa44ec28bf4a3b2d940e3f4a924ba18416140667

t/Dockerfile

@@ -5,10 +5,11 @@ FROM docker.mgm.sipwise.com/sipwise-jessie:latest
 # is updated with the current date. It will force refresh of all
 # of the base images and things like `apt-get update` won't be using
 # old cached versions when the Dockerfile is built.
-ENV REFRESHED_AT 2016-01-27
+ENV REFRESHED_AT 2017-06-30
 
-# TODO - the release-trunk-jessie is too dynamic yet, though required build deps
-RUN echo "deb https://deb.sipwise.com/autobuild/ release-trunk-jessie main" >>/etc/apt/sources.list
+# files that get-code generates
+COPY t/sources.list.d/builddeps.list /etc/apt/sources.list.d/
+COPY t/sources.list.d/preferences /etc/apt/preferences.d/
 
 RUN apt-get update
 RUN apt-get install --assume-yes \
@@ -35,13 +36,22 @@ WORKDIR /code
 ################################################################################
 # Instructions for usage
 # ----------------------
-# When you want to build the base image from scratch (jump to the next section if you don't want to build yourself!):
-# % docker build --no-cache --tag="rate-o-mat-functional-tests-jessie" .
-# % docker run --rm -i -t -v $(pwd)/../:/code:rw rate-o-mat-functional-tests-jessie:latest bash
+# When you want to build the base image from scratch
+# (jump to the next section if you don't want to build yourself!):
+#
+# you need to put the proper NGCP sources at t/sources.list.d/builddeps.list
+# for instance, trunk:
+# echo "deb https://deb.sipwise.com/autobuild/ release-trunk-jessie main" > /
+#  t/sources.list.d/builddeps.list
+#
+# NOTE: run the following command from root folder of git repository:
+# % docker build --no-cache --tag="rate-o-mat-functional-tests-jessie" -f t/Dockerfile .
+# % docker run --rm -i -t -v $(pwd):/code:rw rate-o-mat-functional-tests-jessie:latest bash
 #
 # Use the existing docker image:
 # % docker pull docker.mgm.sipwise.com/rate-o-mat-functional-tests-jessie
-# % docker run --rm -i -t -v $(pwd)/../:/code:rw docker.mgm.sipwise.com/rate-o-mat-functional-tests-jessie:latest bash
+# NOTE: run the following command from root folder of git repository:
+# % docker run --rm -i -t -v $(pwd):/code:rw docker.mgm.sipwise.com/rate-o-mat-functional-tests-jessie:latest bash
 #
 # Inside docker:
 #   cd /code && ./t/testrunner $IP_OF_NGCP_SYSTEM # IP_OF_NGCP_SYSTEM can be e.g. IP of a `vagrant up ce-trunk` system (eth1)