feat(ci): automate the creation of emacs-builder image - fix #4 (#13)

Author: mpsq

.github/workflows/build-docker-image.yml

@@ -0,0 +1,37 @@
+on:
+  schedule:
+    - cron: "30 11 * * 0"
+
+jobs:
+  image:
+    runs-on: ubuntu-20.04
+    steps:
+      - name: Checkout the repo
+        uses: actions/checkout@v2
+      - name: Import environment variables
+        shell: bash
+        run: |
+          while read line; do
+            echo "$line" >> $GITHUB_ENV
+          done < assets/variables
+      - name: Set up Docker buildx
+        id: buildx
+        uses: docker/setup-buildx-action@master
+      - name: Login to Docker Hub
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          file: ./Dockerfile
+          builder: ${{ steps.buildx.outputs.name }}
+          push: true
+          tags: mpsq/emacs-builder:latest
+          build-args: |
+            UPSTREAM_BRANCH=${{ env.UPSTREAM_BRANCH }}
+            UPSTREAM_REPO=${{ env.UPSTREAM_REPO }}
+            USR=${{ env.USR }}
+            USR_HOME=${{ env.USR_HOME }}

Dockerfile

@@ -1,16 +1,8 @@
 #
 # This Dockerfile is used to build the image "mpsq/emacs-builder".
-# Link: https://hub.docker.com/repository/docker/mpsq/emacs-builder
+# https://hub.docker.com/repository/docker/mpsq/emacs-builder
 #
-# What is the point of this?
-#   - Have an Archlinux environment
-#   - Pull and compile Emacs so it is much faster to produce subsequent binaries
-#
-# This image is obviously then used in the GitHub action to compile Emacs.
-#
-# At the moment, this image is built manually from times to times (= very
-# infrequently). In the future, I might get CI to do it, maybe on a monthly
-# basis.
+# This image is then used in GitHub actions to compile Emacs.
 #
 FROM archlinux:base-devel
 
@@ -71,6 +63,8 @@ USER $USR
 
 SHELL ["/bin/bash", "-c"]
 
+# We compile Emacs in order to cache artifacts in the image and get better
+# compilation time in subsequent builds.
 RUN \
   cp /scripts/pull.bash . && \
   cp /assets/PKGBUILD . && \