infra: image: switch to using ${{ vars.REGISTRY_URL }}

Doing this so I can change this site wide in the future without anything breaking

.docker/Dockerfile

@@ -31,4 +31,6 @@ USER gentooligan
 
 WORKDIR /workspace
 
-ENTRYPOINT /bin/bash
+ENTRYPOINT ["/entrypoint.sh"]
+
+CMD ["/bin/bash"]

.docker/entrypoint.sh

@@ -0,0 +1,6 @@
+#!/usr/bin/env sh
+
+
+source /etc/profile
+source /lib/gentoo/functions.sh
+exec "$@"

.gitea/workflows/gentoo-utils.yml

@@ -1,10 +1,6 @@
 name: Gentoo Utils
 
-on:
-  push:
-    branches: [master]
-  pull_request:
-    branches: [master]
+on: [push]
 
 jobs:
   build-oci-image:
@@ -18,39 +14,60 @@ jobs:
 
       - name: Check for changes before building
         id: image-changes
+        # build image only if 1. changes are detected or 2. an image for the working branch doesnt exist
         run: |
-          echo "branch_name=${GITHUB_HEAD_REF:-${GITHUB_REF#refs/heads/}}" >> $GITEA_OUTPUT
-          if ! git diff ${{ gitea.event.before }} ${{ gitea.sha }} --no-patch --exit-code .docker; then
-            echo changes_detected=true >> $GITEA_OUTPUT
+          branch_name="${GITHUB_HEAD_REF:-${GITHUB_REF#refs/heads/}}"
+
+          if [[ "$branch_name" == "${{ gitea.event.repository.default_branch }}" ]]; then
+            image_tag=latest
           else
-            echo changes_detected=false >> $GITEA_OUTPUT
+            image_tag=$branch_name
           fi
+
+          echo "branch_name=$branch_name" >> $GITEA_OUTPUT
+          # slugify
+          image_tag="$(echo "$image_tag" | sed -E 's/[^a-zA-Z0-9]/-/g')"
+          echo "image_tag=$image_tag" >> $GITEA_OUTPUT
+
+          if ! git diff ${{ gitea.event.before }} ${{ gitea.sha }} --no-patch --exit-code .docker; then
+            build_image=true
+          else
+            if ! docker manifest inspect ${{ vars.REGISTRY_URL }}/${{ gitea.repository }}:${image_tag} >/dev/null 2>&1; then
+              build_image=true
+            else
+              build_image=false
+            fi
+          fi
+
+          echo "build_image=$build_image" >> $GITEA_OUTPUT
           cat $GITEA_OUTPUT
       - name: Set up Docker buildx
-        if: steps.image-changes.outputs.changes_detected == 'true'
+        if: steps.image-changes.outputs.build_image == 'true'
         uses: docker/setup-buildx-action@v3
 
       - name: Log in to Github Container Registry
-        if: steps.image-changes.outputs.changes_detected == 'true'
+        if: steps.image-changes.outputs.build_image == 'true'
         uses: docker/login-action@v3
         with:
-          registry: git.epenguin.net
+          registry: ${{ vars.REGISTRY_URL }}
           username: ${{ vars.CI_BOT_USERNAME }}
           password: ${{ secrets.CI_BOT_TOKEN }}
 
       - name: Build and push
-        if: steps.image-changes.outputs.changes_detected == 'true'
+        if: steps.image-changes.outputs.build_image == 'true'
         uses: docker/build-push-action@v6
         with:
           push: true
-          tags: git.epenguin.net/${{ gitea.repository }}:latest
+          tags: ${{ vars.REGISTRY_URL }}/${{ gitea.repository }}:${{ steps.image-changes.outputs.image_tag }}
           context: "{{defaultContext}}:.docker"
+    outputs:
+      image_tag: ${{ steps.image-changes.outputs.image_tag }}
 
   build:
     runs-on: brutalisk
-    container:
-      image: git.epenguin.net/gentoo-utils/gentoo-utils-gitea:latest
     needs: build-oci-image
+    container:
+      image: ${{ vars.REGISTRY_URL }}/${{ gitea.repository }}:${{ needs.build-oci-image.outputs.image_tag }}
     steps:
       - name: Checkout repo
         uses: actions/checkout@v5