describe how to build the image with a Bake file

Author: 1ma

.github/workflows/build.yml

@@ -27,6 +27,10 @@ jobs:
         runner:
           - "ubuntu-24.04"
           - "ubuntu-24.04-arm"
+    env:
+      CONTEXT: ${{ matrix.knots.context }}
+      RUNNER: ${{ matrix.runner }}
+      VERSION: ${{ matrix.knots.version }}
     steps:
       - uses: actions/checkout@v5
       - uses: docker/setup-buildx-action@v3
@@ -35,17 +39,12 @@ jobs:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
-      - uses: docker/build-push-action@v6
+      - uses: docker/bake-action@v6
         with:
-          build-args: |
-            KNOTS_VERSION=${{ matrix.knots.version }}
-          cache-from: type=registry,ref=ghcr.io/bcnbitcoinonly/bitcoin:v${{ matrix.knots.version }}-${{ matrix.runner }}
-          cache-to: type=inline
-          context: ${{ matrix.knots.context }}
           provenance: false
           push: true
           sbom: false
-          tags: ghcr.io/bcnbitcoinonly/bitcoin:v${{ matrix.knots.version }}-${{ matrix.runner }}
+          targets: knots
 
   merge:
     name: Merge v${{ matrix.knots_version }}

docker-bake.hcl

@@ -0,0 +1,34 @@
+variable "CONTEXT" {
+  type = string
+  default = "cmake"
+  description = "autotools up to v28.1.knots20250305, cmake after"
+}
+
+variable "RUNNER" {
+  type = string
+  default = "ubuntu-24.04"
+  description = "Runner that built the image"
+}
+
+variable "VERSION" {
+  type = string
+  default = "29.2.knots20251110"
+  description = "Version of Knots to build"
+}
+
+group "default" {
+  targets = ["knots"]
+}
+
+target "knots" {
+  args = {
+    KNOTS_VERSION = "${VERSION}"
+  }
+  context = "${CONTEXT}"
+  cache-to = [{type = "inline"}]
+  cache-from = [{
+    type = "registry"
+    ref = "ghcr.io/bcnbitcoinonly/bitcoin:v${VERSION}-${RUNNER}"
+  }]
+  tags = ["ghcr.io/bcnbitcoinonly/bitcoin:v${VERSION}-${RUNNER}"]
+}