Add github actions workflow

.github/workflows/build.yaml

@@ -0,0 +1,94 @@
+name: build
+
+on: [push]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        version:
+          - '0.17'
+          - '0.17/alpine'
+          - '0.15'
+          - '0.15/alpine'
+      fail-fast: false
+    steps:
+      - name: Set up Docker Buildx
+        uses: crazy-max/ghaction-docker-buildx@v1
+
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Prepare Docker build
+        id: prepare
+        run: |
+          function version { echo "$@" | awk -F. '{ printf("%d%03d%03d%03d\n", $1,$2,$3,$4); }'; }
+          BITCOIN_GOLD_VERSION=${{matrix.version}}
+          LATEST_BITCOIN_GOLD_MAJOR_VERSION=$(ls  | grep 0 | sort -n | tail -n 1)
+          PUSH=false
+          REPO=uphold/bitcoin-gold
+          TAGS=()
+          if [[ $GITHUB_REF == refs/tags/* ]]; then
+            TAG=${GITHUB_REF#refs/tags/}
+            PUSH=true
+            if [[ ${BITCOIN_GOLD_VERSION} == *"alpine"* ]]; then
+              TAGS+=("$REPO:$TAG-alpine")
+            else
+              TAGS+=("$REPO:$TAG")
+            fi
+            TAG_MAJOR_MINOR=$(echo $TAG | cut -c -4)
+            if [ $(version ${TAG_MAJOR_MINOR}) -ne $(version ${BITCOIN_GOLD_VERSION}) ]; then
+              echo "Skipping build of base image $BITCOIN_GOLD_VERSION/ as ${TAG} is targeted at ${TAG_MAJOR_MINOR}/"
+              exit 0
+            fi
+          else
+            TAGS=("$REPO:${BITCOIN_GOLD_VERSION/\//-}")
+            if [ $(version ${BITCOIN_GOLD_VERSION}) -ge $(version ${LATEST_BITCOIN_GOLD_MAJOR_VERSION}) ]; then
+              echo "Version $(version ${BITCOIN_GOLD_VERSION}) is greater than or equal to $(version ${LATEST_BITCOIN_GOLD_MAJOR_VERSION}), tagging as latest"
+              if [[ ${BITCOIN_GOLD_VERSION} != *"alpine"* ]]; then
+                TAGS+=("$REPO:latest")
+              else
+                TAGS+=("$REPO:alpine")
+              fi
+            fi
+            if [ $GITHUB_REF == "refs/heads/master" ]; then
+              PUSH=true
+            fi
+          fi
+          echo ::set-output name=build_date::$(date -u +'%Y-%m-%dT%H:%M:%SZ')
+          echo ::set-output name=push::${PUSH}
+          echo ::set-output name=tags::${TAGS[@]}
+          echo ::set-env name=build::true
+      - if: env.build == 'true'
+        name: Login into Docker Hub
+        env:
+          DOCKER_HUB_PASSWORD: ${{ secrets.DOCKER_HUB_PASSWORD }}
+          DOCKER_HUB_USERNAME: ${{ secrets.DOCKER_HUB_USERNAME }}
+        run: |
+          docker login --username ${DOCKER_HUB_USERNAME} --password ${DOCKER_HUB_PASSWORD}
+      - if: env.build == 'true'
+        name: Build Docker image
+        run: |
+          TAGS=(${{ steps.prepare.outputs.tags }})
+          echo "Build date: ${{ steps.prepare.outputs.build_date }}"
+          echo "Push: ${{ steps.prepare.outputs.push }}"
+          echo "Tags: ${{ steps.prepare.outputs.tags }}"
+          echo docker buildx build \
+            --output "type=image,push=${{steps.prepare.outputs.push}}" \
+            --progress=plain \
+            --build-arg "BUILD_DATE=${{ steps.prepare.outputs.build_date }}" \
+            --build-arg "VCS_REF=${GITHUB_SHA::8}" \
+            $(printf "%s" "${TAGS[@]/#/ --tag }" ) \
+            ${{ matrix.version }}/
+          docker buildx build \
+            --output "type=image,push=${{steps.prepare.outputs.push}}" \
+            --progress=plain \
+            --build-arg "BUILD_DATE=${{ steps.prepare.outputs.build_date }}" \
+            --build-arg "VCS_REF=${GITHUB_SHA::8}" \
+            $(printf "%s" "${TAGS[@]/#/ --tag }" ) \
+            ${{ matrix.version }}/
+      - if: env.build == 'true'
+        name: Clear Docker credentials
+        run: |
+          rm -f ${HOME}/.docker/config.json