Add workflow to build docker images for specific branches

.github/workflows/docker-branch.yml

@@ -0,0 +1,42 @@
+name: Docker Image for specific branch
+
+on:
+  workflow_dispatch:
+    inputs:
+      branch:
+        description: 'branch or tag to build'
+        required: true
+
+env:
+  ORG: timescaledev
+  TS_VERSION: ${{ github.event.inputs.version }}
+  PLATFORM: linux/amd64
+
+jobs:
+
+  # Build ubuntu TimescaleDB images for both TSL and OSS code.
+  timescaledb:
+
+    name: PG${{ matrix.pg }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        pg: [14]
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Set up Docker Buildx
+      id: buildx
+      uses: docker/setup-buildx-action@v1
+
+    - name: Linux available buildx platforms
+      run: echo ${{ steps.buildx.outputs.platforms }}
+
+    - name: Login to DockerHub Registry
+      run: echo ${{ secrets.DOCKERHUB_TOKEN }} | docker login -u ${{ secrets.DOCKERHUB_USER }} --password-stdin
+
+    - name: Build and push nightly Docker image for TimescaleDB
+      run: make multi ORG=$ORG PG_VER=pg${{ matrix.pg }} TS_VERSION=$TS_VERSION PLATFORM=$PLATFORM TAG="-t timescaledev/timescaledb:branch-${TS_VERSION}-pg${{ matrix.pg }}"
+