Add GitHub Actions workflow to build and push Docker image to GHCR

Author: TG9541

.dockerignore

@@ -0,0 +1,4 @@
+.git
+.gitignore
+README.md
+LICENSE

.github/workflows/build-push.yml

@@ -0,0 +1,55 @@
+name: Build and push Docker image
+
+on:
+  push:
+    branches: [ main, master ]
+    tags: [ 'v*' ]
+  pull_request:
+    branches: [ main, master ]
+  schedule:
+    - cron: '0 0 * * 0'  # Weekly
+
+jobs:
+  build-push:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
+      - name: Log in to GHCR
+        if: github.event_name != 'pull_request'
+        uses: docker/login-action@v2
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v4
+        with:
+          images: ghcr.io/tg9541/docker-sdcc
+          tags: |
+            type=ref,event=branch
+            type=ref,event=pr
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=semver,pattern={{major}}
+            type=sha,prefix={{branch}}-
+            type=raw,value=3.9.0,enable={{is_default_branch}}
+
+      - name: Build and push
+        uses: docker/build-push-action@v4
+        with:
+          context: .
+          push: ${{ github.event_name != 'pull_request' }}
+          tags: ghcr.io/tg9541/docker-sdcc:3.9.0
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max

README.md

@@ -7,18 +7,25 @@ This repository contains all that's needed for building and testing TG9541/STM8E
 * telnet for debugging STM8 code with uCsim
 
 The corresponding Docker Hub repository is [tg9541/docker-sdcc](https://hub.docker.com/r/tg9541/docker-sdcc/builds/).
+The GitHub Container Registry image is [ghcr.io/tg9541/docker-sdcc](https://github.com/TG9541/docker-sdcc/pkgs/container/docker-sdcc).
 
 To build it run:
 ```
 docker build -t docker-sdcc .
 ```
 
-To publish it run:
+To publish to Docker Hub:
 ```
 docker tag docker-sdcc <DockerId>/docker-sdcc
 docker push <DockerId>/docker-sdcc
 ```
 
+To publish to GitHub Container Registry:
+```
+docker tag docker-sdcc ghcr.io/tg9541/docker-sdcc:3.9.0
+docker push ghcr.io/tg9541/docker-sdcc:3.9.0
+```
+
 The following builds the W1209 binary, runs it in uCsim, compiles the code in W1209/board.fs, and dumps the Flash memory to out/W1209/W1209-forth.ihx:
 ```
 docker run -ti -v `pwd`:/home docker-sdcc /bin/sh -c "cd /home && make BOARD=W1209 forth"