cosmos testnet dockerfile

Dockerfile

# vi: set ft=dockerfile :
# example usage
# docker build -t cosmos .
# docker run -d -v cosmos-data:/opt/cosmos --rm -ti --name cosmos-1 cosmos
# docker exec -it cosmos-1 sh
# /go/bin/basecli --home $BASECOIN_HOME keys add default
# /go/bin/gaiad --home $GAIAD_HOME show_validator
FROM golang:1-alpine

RUN apk add --no-cache git make

RUN mkdir -p /go/src/github.com/cosmos/
WORKDIR /go/src/github.com/cosmos/
RUN git clone https://github.com/cosmos/cosmos-sdk

WORKDIR /go/src/github.com/cosmos/cosmos-sdk

RUN git fetch --all
RUN git checkout develop
RUN make get_tools
RUN make get_vendor_deps
RUN make install
RUN make install_examples

ENV GAIAD_HOME=/opt/cosmos/gaiad
ENV BASECOIN_HOME=/opt/cosmos/basecoin
RUN mkdir -p $GAIAD_HOME

RUN /go/bin/gaiad --home $GAIAD_HOME init

RUN rm $GAIAD_HOME/config/genesis.json $GAIAD_HOME/config/config.toml
RUN wget -q -O $GAIAD_HOME/config/genesis.json https://raw.githubusercontent.com/tendermint/testnets/master/gaia-3006/gaia/genesis.json
RUN wget -q -O $GAIAD_HOME/config/config.toml https://raw.githubusercontent.com/tendermint/testnets/master/gaia-3006/gaia/config.toml

CMD /go/bin/gaiad --home $GAIAD_HOME start
EXPOSE 46656

Hi,
I have customised cosmos-sdk but when i am running make install through docker file its not pointing to my customised sdk and returning error as undefined . So , what to do so that make install download from my customised cosmos-sdk