add docker build action

.github/workflows/docker.yml

@@ -0,0 +1,73 @@
+name: Netdisco Docker Images
+on:
+  workflow_dispatch:
+    inputs:
+      debug_enabled:
+        description: 'Run debugging enabled (https://github.com/marketplace/actions/debugging-with-tmate)'     
+        required: false
+        default:  false
+#      success_irc_squawk:
+#        description: 'Squawk to IRC on success'     
+#        required: false
+#        default:  false
+  push:
+    tags:
+      - '2.[0-9][0-9][0-9][0-9][0-9][0-9]'
+jobs:
+  build_docker_images:
+    name: Build Docker Images
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: /github/workspace/netdisco-docker/netdisco-docker
+    steps:
+    - name: Get the Tag
+      id: get_refs
+      run: |
+        echo "TAG=${GITHUB_REF#refs/tags/}" >> $GITHUB_ENV
+        echo "IMAGE_ROOT=netdisco:${GITHUB_REF#refs/tags/}" >> $GITHUB_ENV
+    - name: Check out latest code
+      uses: actions/checkout@v1
+      with:
+        repo: 'netdisco/netdisco-docker'
+
+    - name: Build netdisco-postgresql
+      id: build_netdisco_postgresql
+      run: |
+        cd netdisco-postgresql
+        docker build -t ${IMAGE_ROOT}-postgresql \
+              --build-arg BUILD_DATE=`date -u +"%Y-%m-%dT%H:%M:%SZ"` \
+              --build-arg TAG=${TAG} \
+              --build-arg COMMITTISH=${TAG} .
+
+    - name: Retag all images
+      run: |
+        for image in postgresql; do
+          docker tag ${IMAGE_ROOT}-$image netdisco/${IMAGE_ROOT}-$image
+          docker tag ${IMAGE_ROOT}-$image netdisco/netdisco:latest-$image
+        done
+
+#    - name: IRC upload failure notification
+#      uses: Gottox/irc-message-action@v2
+#      if: (! github.event.inputs.debug_enabled) && startsWith(github.ref, 'refs/tags/')
+#      with:
+#        channel: '#netdisco'
+#        nickname: github-actions
+#        message: |-
+#          🤖 Failed to upload Netdisco release ${{ steps.get_refs.outputs.RELEASE_TAG }} to CPAN! 😭
+#          👀 https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}
+#    - name: IRC upload success notification
+#      uses: Gottox/irc-message-action@v2
+#      if: (! github.event.inputs.debug_enabled) && startsWith(github.ref, 'refs/tags/')
+#      with:
+#        channel: '#netdisco'
+#        nickname: github-actions
+#        message: |-
+#          🤖 Uploaded Netdisco release ${{ steps.get_refs.outputs.RELEASE_TAG }} to CPAN 🎉
+
+    - name: Setup tmate session
+      uses: mxschmitt/action-tmate@v3
+      if: always() && github.event.inputs.debug_enabled && (github.event_name == 'workflow_dispatch')
+      with:
+        sudo: true
+