feat: add dockerfile build arguments

README.md

@@ -218,3 +218,16 @@ Example: `thetadev256/test-actions-helloworld2:main`
 Full reference to the built image with registry and tag.
 
 Example: `thetadev256/test-actions-helloworld2:main`
+
+## Dockerfile build arguments
+
+Action-Kaniko automatically sets build arguments to allow for different dockerfile actions
+depending on the OS and architecture the image is build for.
+
+The supported arguments are:
+
+- `TARGETPLATFORM` (example: linux/amd64)
+- `TARGETOS` (example: linux)
+- `TARGETARCH` (example: amd64)
+- `TARGETARCH_ALT` (alternative architecture name, x86_64 for amd64, otherwise the same as TARGETARCH)
+- `TARGETVARIANT` (third docker platform parameter like ARM version)

entrypoint.sh

@@ -96,7 +96,16 @@ if [ -n "$INPUT_PLATFORMS" ]; then
         DESTINATION="--no-push --tarPath /kaniko/build/${platformFn}.tar --destination $IMAGE"
         DIGEST="--image-name-tag-with-digest-file=/kaniko/build/${platformFn}_image-tag-digest"
 
-        runKaniko "${ARGS} --custom-platform=${platform} $DESTINATION $DIGEST"
+        targetos=$(echo "$platform" | cut -d/ -f1)
+        targetarch=$(echo "$platform" | cut -d/ -f2)
+        targetvariant=$(echo "$platform" | cut -d/ -f3)
+
+        case "$targetarch" in
+            'amd64') targetarchAlt="x86_64" ;;
+            *) targetarchAlt="$targetarch" ;;
+        esac
+
+        runKaniko "${ARGS} --custom-platform=${platform} --build-arg TARGETPLATFORM='${platform}' --build-arg TARGETOS='${targetos}' --build-arg TARGETARCH='${targetarch}' --build-arg TARGETARCH_ALT='${targetarchAlt}' --build-arg TARGETVARIANT='${targetvariant}' $DESTINATION $DIGEST"
 
         echo "✅ $platform image built: $(head -n 1 "/kaniko/build/${platformFn}_image-tag-digest")"
     done