Build Docker images and push to ghcr.io.

Also slim down the Dockerfile to only include Elvish.

.github/workflows/docker.yml

@@ -0,0 +1,32 @@
+name: docker
+
+on:
+  push:
+
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+      - name: Log in to the Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Extract metadata for Docker
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ghcr.io/${{ github.repository }}
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}

Dockerfile

@@ -1,13 +1,9 @@
-FROM golang:1.20-alpine as builder
+FROM golang:1.22-alpine3.19 as builder
 RUN apk add --no-cache --virtual build-deps make git
 # Build Elvish
 COPY . /go/src/src.elv.sh
 RUN make -C /go/src/src.elv.sh get
 
-FROM alpine:3.18
-RUN adduser -D elf
-RUN apk update && apk add tmux mandoc man-pages vim curl sqlite git
+FROM alpine:3.19
 COPY --from=builder /go/bin/elvish /bin/elvish
-USER elf
-WORKDIR /home/elf
 CMD ["/bin/elvish"]