ci: Split stable and testing builds apart (#271)

Splits stable and testing builds apart so that only the `testing` tags
are updated when the `main` branch is, and `stable` updates only once
per day.

Closes #270

.github/workflows/build-stable.yml

@@ -0,0 +1,26 @@
+name: Zeliblue Stable
+on:
+  schedule:
+    - cron:
+        "00 06 * * *" # build at 06:00 UTC every day
+        # (20 minutes after last ublue images start building)
+  pull_request:
+    branches:
+      - main
+    paths-ignore: # don't rebuild if only documentation has changed
+      - "**.md"
+  workflow_dispatch: # allow manually triggering builds
+
+jobs:
+  build_gnome:
+    name: Zeliblue GNOME
+    uses: ./.github/workflows/reusable-build.yml
+    secrets: inherit
+    with:
+      recipe: gnome/zeliblue.yml
+  build_plasma:
+    name: Zeliblue Plasma
+    uses: ./.github/workflows/reusable-build.yml
+    secrets: inherit
+    with:
+      recipe: plasma/zeliblue-kinoite.yml

.github/workflows/build-testing.yml

@@ -0,0 +1,27 @@
+name: Zeliblue Testing
+on:
+  schedule:
+    - cron:
+        "00 06 * * *" # build at 06:00 UTC every day
+        # (20 minutes after last ublue images start building)
+  push:
+    branches:
+      - main
+    paths-ignore: # don't rebuild if only documentation has changed
+      - "**.md"
+  pull_request:
+  workflow_dispatch: # allow manually triggering builds
+
+jobs:
+  build_gnome:
+    name: Zeliblue GNOME Testing
+    uses: ./.github/workflows/reusable-build.yml
+    secrets: inherit
+    with:
+      recipe: gnome/zeliblue-testing.yml
+  build_plasma:
+    name: Zeliblue COSMIC Testing
+    uses: ./.github/workflows/reusable-build.yml
+    secrets: inherit
+    with:
+      recipe: cosmic/zeliblue-cosmic.yml

.github/workflows/reusable-build.yml

@@ -0,0 +1,29 @@
+name: Reusable Build and Push
+on:
+  workflow_call:
+    inputs:
+      recipe:
+        description: "Recipes to build"
+        required: true
+        type: string
+
+jobs:
+  bluebuild:
+    name: Build Custom Image
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+      id-token: write
+    steps:
+      # the build is fully handled by the reusable github action
+      - name: Build Custom Image
+        uses: blue-build/[email protected]
+        with:
+          recipe: ${{ inputs.recipe }}
+          cosign_private_key: ${{ secrets.SIGNING_SECRET }}
+          registry_token: ${{ github.token }}
+          pr_event_number: ${{ github.event.number }}
+
+          # enabled by default, disable if your image is small and you want faster builds
+          maximize_build_space: false