--- a/Dockerfile	Tue Jul 04 00:00:58 2017 +0300
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,21 +0,0 @@
-FROM debian:stretch
-
-RUN apt-get update && apt-get install -y \
-    build-essential \
-    libc6-dev libpng-dev \
-    python python-dev python-pip virtualenv
-
-ADD . /src/pngtile
-
-WORKDIR /src/pngtile
-
-RUN make
-
-RUN virtualenv /opt/pngtile
-
-RUN make -B install PREFIX=/opt/pngtile
-RUN /opt/pngtile/bin/pip install -r requirements.txt
-RUN /opt/pngtile/bin/python setup.py build_ext -I /opt/pngtile/include -L /opt/pngtile/lib -R /opt/pngtile/lib
-RUN /opt/pngtile/bin/python setup.py install
-
-WORKDIR /opt/pngtile

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Dockerfile.common	Sat Jul 15 11:36:03 2017 +0300
@@ -0,0 +1,20 @@
+FROM debian:stretch
+
+RUN apt-get update && apt-get install -y \
+    build-essential \
+    libc6-dev libpng-dev \
+    python python-dev python-pip virtualenv
+
+RUN mkdir -p /src/pngtile && virtualenv /opt/pngtile
+ADD requirements.txt /src/pngtile
+
+WORKDIR /src/pngtile
+RUN /opt/pngtile/bin/pip install -r requirements.txt
+
+ADD . /src/pngtile
+
+RUN make -B install PREFIX=/opt/pngtile
+RUN /opt/pngtile/bin/python setup.py build_ext -I /opt/pngtile/include -L /opt/pngtile/lib -R /opt/pngtile/lib
+RUN /opt/pngtile/bin/python setup.py install
+
+WORKDIR /opt/pngtile