ci: move dev-container to only as-needed

.devcontainer/BUILD.bazel

@@ -6,5 +6,5 @@ container_push(
     image = "@dev-container//image:dockerfile_image.tar",
     registry = "docker.pkg.github.com",
     repository = "roleypoly/roleypoly/dev-container",
-    tag = "{STABLE_GIT_BRANCH}" if "{STABLE_GIT_BRANCH}" != "main" else "latest",
+    tag = "{STABLE_GIT_BRANCH}",
 )

.github/workflows/build.yml

@@ -57,11 +57,3 @@ jobs:
         with:
           name: manifest.json
           path: manifest.json
-
-      - name: Publish Dev Container Image
-        if: github.ref == 'refs/heads/main'
-        run: |
-          "${GITHUB_WORKSPACE}/bin/bazel" run \
-            --stamp \
-            --workspace_status_command hack/workspace_status.sh\
-              //.devcontainer:publish-dev-container

.github/workflows/dev-container.yml

@@ -0,0 +1,34 @@
+name: Build Dev Container
+
+on:
+  push:
+    paths:
+      - .devcontainer/Dockerfile
+  schedule:
+    - cron: "0 12 * * 2" # 12 noon every tuesday
+
+jobs:
+  dev_container_build:
+    name: Bazel Build (Dev Container)
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@master
+      - name: Mount bazel cache
+        uses: actions/cache@v1
+        with:
+          path: "/home/runner/.cache/bazel"
+          key: bazel
+
+      - name: Install bazelisk
+        run: |
+          curl -LO "https://github.com/bazelbuild/bazelisk/releases/download/v1.1.0/bazelisk-linux-amd64"
+          mkdir -p "${GITHUB_WORKSPACE}/bin/"
+          mv bazelisk-linux-amd64 "${GITHUB_WORKSPACE}/bin/bazel"
+          chmod +x "${GITHUB_WORKSPACE}/bin/bazel"
+      
+      - name: Build & Publish Dev Container
+        run: |
+        "${GITHUB_WORKSPACE}/bin/bazel" run \
+          --stamp \
+          --workspace_status_command hack/workspace_status.sh\
+            //.devcontainer:publish-dev-container