Add a dockerfile, end-to-end sanity test

Could potentially form the basis of (or simplify) more testing involving
environment variables and filesystem setup too.

Closes tfutils#241

.github/workflows/test.yml

@@ -30,6 +30,23 @@ jobs:
         run: './test/run.sh'
         shell: 'bash'
 
+      - uses: 'docker/setup-buildx-action@v2'
+        if: contains(matrix.os, 'ubuntu')
+        with:
+          install: true
+      - uses: 'docker/build-push-action@v3'
+        if: contains(matrix.os, 'ubuntu')
+        with:
+          context: .
+          load: true
+          tags: "tfenv-terraform:${GITHUB_SHA}"
+      - name: 'Check Dockerfile'
+        if: contains(matrix.os, 'ubuntu')
+        run: |
+          expect=1.2.3;
+          got="$(docker run -e "TFENV_TERRAFORM_VERSION=${expect}" "tfenv-terraform:${GITHUB_SHA}" version)";
+          echo "${got}" | tee /dev/stderr | grep -e 'Terraform v1.2.3'
+
   # When we push to master, test everything in order to guarantee releases
   test-master-pushes:
     if: github.event_name == 'push' && github.ref == 'refs/heads/master'
@@ -51,3 +68,20 @@ jobs:
       - name: 'Run all tests'
         run: './test/run.sh'
         shell: 'bash'
+
+      - uses: 'docker/setup-buildx-action@v2'
+        if: contains(matrix.os, 'ubuntu')
+        with:
+          install: true
+      - uses: 'docker/build-push-action@v3'
+        if: contains(matrix.os, 'ubuntu')
+        with:
+          context: .
+          load: true
+          tags: 'tfenv-terraform:latest'
+      - name: 'Check Dockerfile'
+        if: contains(matrix.os, 'ubuntu')
+        run: |
+          expect=1.2.3;
+          got="$(docker run -e "TFENV_TERRAFORM_VERSION=${expect}" tfenv-terraform:latest version)";
+          echo "${got}" | tee /dev/stderr | grep -e 'Terraform v1.2.3'

Dockerfile

@@ -0,0 +1,27 @@
+ARG BASH_VERSION=5
+FROM "docker.io/bash:${BASH_VERSION}"
+
+# Runtime dependencies
+RUN apk add --no-cache --purge \
+    curl \
+    ;
+
+ARG TFENV_VERSION=3.0.0
+RUN wget -O /tmp/tfenv.tar.gz "https://github.com/tfutils/tfenv/archive/refs/tags/v${TFENV_VERSION}.tar.gz" \
+    && tar -C /tmp -xf /tmp/tfenv.tar.gz \
+    && mv "/tmp/tfenv-${TFENV_VERSION}/bin"/* /usr/local/bin/ \
+    && mkdir -p /usr/local/lib/tfenv \
+    && mv "/tmp/tfenv-${TFENV_VERSION}/lib" /usr/local/lib/tfenv/ \
+    && mv "/tmp/tfenv-${TFENV_VERSION}/libexec" /usr/local/lib/tfenv/ \
+    && mkdir -p /usr/local/share/licenses \
+    && mv "/tmp/tfenv-${TFENV_VERSION}/LICENSE" /usr/local/share/licenses/tfenv \
+    && rm -rf /tmp/tfenv* \
+    ;
+ENV TFENV_ROOT /usr/local/lib/tfenv
+
+ENV TFENV_CONFIG_DIR /var/tfenv
+VOLUME /var/tfenv
+
+# Default to latest; user-specifiable
+ENV TFENV_TERRAFORM_VERSION latest
+ENTRYPOINT ["/usr/local/bin/terraform"]