ci: publish only a latest image tag, built from main

Drops version tag builds and the main tag. Images report the short
commit SHA as their version.

.github/workflows/images.yml

@@ -7,7 +7,6 @@ name: Images
 on:
   push:
     branches: [main]
-    tags: ['v*.*.*']
   workflow_dispatch:
 
 permissions:
@@ -39,6 +38,12 @@ jobs:
         shell: bash
         run: echo "name=${GITHUB_REPOSITORY_OWNER,,}" >> "$GITHUB_OUTPUT"
 
+      # Shown in Settings, since images carry no version number
+      - name: Name the version
+        id: version
+        shell: bash
+        run: echo "sha=${GITHUB_SHA::7}" >> "$GITHUB_OUTPUT"
+
       - uses: docker/setup-buildx-action@v3
 
       - uses: docker/login-action@v3
@@ -51,11 +56,7 @@ jobs:
         uses: docker/metadata-action@v5
         with:
           images: ghcr.io/${{ steps.owner.outputs.name }}/${{ matrix.image }}
-          tags: |
-            type=semver,pattern={{version}}
-            type=semver,pattern={{major}}.{{minor}}
-            type=raw,value=latest,enable=${{ startsWith(github.ref, 'refs/tags/v') }}
-            type=ref,event=branch
+          tags: type=raw,value=latest
 
       - uses: docker/build-push-action@v6
         with:
@@ -65,5 +66,5 @@ jobs:
           labels: ${{ steps.meta.outputs.labels }}
           platforms: linux/amd64
           build-args: |
-            VERSION=${{ steps.meta.outputs.version }}
+            VERSION=${{ steps.version.outputs.sha }}
           provenance: false