Use builder images in dockerfiles

The final tippecanoe image doesn't need the compiler in it. By
using a builder image, we can install the compiler and build
tippecanoe, then copy the results into a smaller final image.

In Travis, run a build that stops on the builder image stage
so that make test can be run in the script stage. In normal
usage for a user that's not necessary. Update the travis image
to bionic, as trusty is now in extended maint - and the only
thing these jobs are doing is running docker.

While we're in there, update centos to centos8 and ubuntu to 20.04,
but add build args that allow overriding that if desired.

Finally, ubuntu doesn't need build-essential, which pulls in all
of the tools needed to build debian packages. Like centos it just
needs gcc, g++ and make.

.dockerignore

@@ -2,4 +2,4 @@
 .gitignore
 .git
 Dockerfile
-Dockerfile.centos7
+Dockerfile.centos

.travis.yml

@@ -6,32 +6,40 @@ sudo: false
 
 matrix:
   include:
-    # test on docker+centos7
+    # test on docker+centos
     - os: linux
       compiler: clang
       services:
        - docker
       sudo: true
-      dist: trusty
-      env: DOCKERFILE=Dockerfile.centos7
+      dist: bionic
+      env: DOCKERFILE=Dockerfile.centos
       before_install: []
+      # build the builder image separately to run the tests
       install:
+        - docker build -t tippecanoe-image-builder -f ${DOCKERFILE} . --target=builder
         - docker build -t tippecanoe-image -f ${DOCKERFILE} .
+      # run tippecanoe --help to make sure runtime libs are correct
       script:
-        - docker run -it tippecanoe-image
+        - docker run -it tippecanoe-image-builder
+        - docker run -it tippecanoe-image tippecanoe --help
     # test on docker+ubuntu
     - os: linux
       compiler: clang
       services:
        - docker
       sudo: true
-      dist: trusty
+      dist: bionic
       env: DOCKERFILE=Dockerfile
       before_install: []
+      # build the builder image separately to run the tests
       install:
+        - docker build -t tippecanoe-image-builder -f ${DOCKERFILE} . --target=builder
         - docker build -t tippecanoe-image -f ${DOCKERFILE} .
+      # run tippecanoe --help to make sure runtime libs are correct
       script:
-        - docker run -it tippecanoe-image
+        - docker run -it tippecanoe-image-builder
+        - docker run -it tippecanoe-image tippecanoe --help
     # debug+integer-santizer build
     - os: linux
       compiler: clang

Dockerfile

@@ -1,13 +1,14 @@
+# Allow setting version as an argument
+ARG UBUNTU_VERSION=20.04
+
 # Start from ubuntu
-FROM ubuntu:16.04
+FROM ubuntu:${UBUNTU_VERSION} as builder
 
 # Update repos and install dependencies
 RUN apt-get update \
-  && apt-get -y upgrade \
-  && apt-get -y install build-essential libsqlite3-dev zlib1g-dev
+  && apt-get -y install make gcc g++ libsqlite3-dev zlib1g-dev
 
-# Create a directory and copy in all files
-RUN mkdir -p /tmp/tippecanoe-src
+# Copy in all files
 WORKDIR /tmp/tippecanoe-src
 COPY . /tmp/tippecanoe-src
 
@@ -17,3 +18,15 @@ RUN make \
 
 # Run the tests
 CMD make test
+
+# Build final image
+FROM ubuntu:${UBUNTU_VERSION}
+
+# Install runtime dependencies
+RUN apt-get update \
+  && apt-get install -y libsqlite3-0 zlib1g \
+  && apt-get clean \
+  && rm -rf /var/lib/apt/lists/*
+
+# Copy built files into final image
+COPY --from=builder /usr/local/ /usr/local/

Dockerfile.centos

@@ -0,0 +1,27 @@
+ARG CENTOS_VERSION=8
+
+# Start from centos
+FROM centos:${CENTOS_VERSION} as builder
+
+# Intall dependencies
+RUN yum install -y make sqlite-devel zlib-devel gcc-c++ diffutils
+
+# Copy in all files
+WORKDIR /tmp/tippecanoe-src
+COPY . /tmp/tippecanoe-src
+
+# Build tippecanoe
+RUN make \
+  && make install
+
+# Run the tests
+CMD make test
+
+# Build final image
+FROM centos:${CENTOS_VERSION}
+
+# Install runtime dependencies
+RUN yum install -y sqlite-libs zlib
+
+# Copy built files into final image
+COPY --from=builder /usr/local/ /usr/local/

README.md

@@ -673,7 +673,7 @@ uses md2man (`gem install md2man`).
 
 Linux:
 
-    sudo apt-get install build-essential libsqlite3-dev zlib1g-dev
+    sudo apt-get install gcc g++ make libsqlite3-dev zlib1g-dev
 
 Then build: