Publish Docker images through CI

Rebuild the images on push to the respective branch.

.github/workflows/docker.yml

@@ -0,0 +1,74 @@
+name: Publish Docker images
+on:
+  push:
+    branches:
+      - dev
+      - beta
+      - stable
+  workflow_dispatch:
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Docker meta
+        id: meta
+        uses: docker/metadata-action@v4
+        with:
+          images: |
+            pwntools/pwntools
+          tags: |
+            type=ref,event=branch
+
+      # Required for subdirectories in Git context
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
+      - name: Login to Docker Hub
+        uses: docker/login-action@v2
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_PASSWORD }}
+
+      - name: Build and push base image
+        uses: docker/build-push-action@v4
+        if: github.event_name == 'workflow_dispatch'
+        with:
+          context: "{{defaultContext}}:extra/docker/base"
+          push: true
+          tags: pwntools/pwntools:base
+
+      - name: Build and push stable image
+        uses: docker/build-push-action@v4
+        if: github.event_name == 'workflow_dispatch' || (github.event_name == 'push' && github.ref == 'refs/heads/stable')
+        with:
+          context: "{{defaultContext}}:extra/docker/stable"
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+
+      - name: Build and push beta image
+        uses: docker/build-push-action@v4
+        if: github.event_name == 'workflow_dispatch' || (github.event_name == 'push' && github.ref == 'refs/heads/beta')
+        with:
+          context: "{{defaultContext}}:extra/docker/beta"
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+
+      - name: Build and push dev image
+        uses: docker/build-push-action@v4
+        if: github.event_name == 'workflow_dispatch' || (github.event_name == 'push' && github.ref == 'refs/heads/dev')
+        with:
+          context: "{{defaultContext}}:extra/docker/dev"
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+
+      - name: Build and push ci image
+        uses: docker/build-push-action@v4
+        if: github.event_name == 'workflow_dispatch' || (github.event_name == 'push' && github.ref == 'refs/heads/dev')
+        with:
+          context: "{{defaultContext}}:travis/docker"
+          push: true
+          tags: pwntools/pwntools:ci
+          labels: ${{ steps.meta.outputs.labels }}