feat: add workflow for promoting 'latest' docker tag (#93)

- Don't automatically promote 'latest' tag

.github/workflows/latest.yaml

@@ -0,0 +1,46 @@
+name: promote-latest
+
+on:
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: "The tag to point latest to"
+        required: true
+
+permissions:
+  actions: read
+  checks: none
+  contents: write
+  deployments: none
+  issues: none
+  packages: write
+  pull-requests: none
+  repository-projects: none
+  security-events: none
+  statuses: none
+
+jobs:
+  manifest:
+    runs-on: ubuntu-22.04
+    needs: release
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+          ref: ${{ github.event.inputs.tag }}
+      - name: Docker Login
+        uses: docker/login-action@v2
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Create Manifest
+        run: |
+          docker manifest create ghcr.io/coder/envbox:latest \
+            --amend ghcr.io/coder/envbox:${{ github.event.inputs.tag }}-amd64 \
+            --amend ghcr.io/coder/envbox:${{ github.event.inputs.tag }}-arm64
+
+      - name: Push Manifest
+        run: |
+          docker manifest push ghcr.io/coder/envbox:latest

.github/workflows/release.yaml

@@ -103,14 +103,9 @@ jobs:
           docker manifest create ghcr.io/coder/envbox:${{ github.event.inputs.version }} \
             --amend ghcr.io/coder/envbox:${{ github.event.inputs.version }}-amd64 \
             --amend ghcr.io/coder/envbox:${{ github.event.inputs.version }}-arm64
-          docker manifest create ghcr.io/coder/envbox:latest \
-            --amend ghcr.io/coder/envbox:${{ github.event.inputs.version }}-amd64 \
-            --amend ghcr.io/coder/envbox:${{ github.event.inputs.version }}-arm64
-
       - name: Push Manifest
         run: |
           docker manifest push ghcr.io/coder/envbox:${{ github.event.inputs.version }}
-          docker manifest push ghcr.io/coder/envbox:latest
 
   tag:
     runs-on: ubuntu-22.04