add docker build image for local dev.

Author: mjudeikis

hack/build-image-docker.sh

@@ -0,0 +1,219 @@
+#!/usr/bin/env bash
+
+# Copyright 2025 The KCP Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Build container images for KCP using Docker
+#
+# This script builds container images using Docker (with or without buildx).
+#
+# Usage examples:
+#   # Build locally with default settings (uses current git commit hash)
+#   ./hack/build-image-docker.sh
+#   
+#   # Build locally with custom repository name
+#   REPOSITORY=my-registry/kcp ./hack/build-image-docker.sh
+#   
+#   # Build locally without pushing (dry run)
+#   DRY_RUN=1 ./hack/build-image-docker.sh
+#   
+#   # Build for specific architectures only
+#   ARCHITECTURES="amd64" ./hack/build-image-docker.sh
+#
+# Environment variables:
+#   REPOSITORY - Override default repository (default: ghcr.io/kcp-dev/kcp)
+#   ARCHITECTURES - Space-separated list of architectures (default: "amd64 arm64")
+#   DRY_RUN - Set to any value to build locally without pushing
+#   KCP_GHCR_USERNAME/KCP_GHCR_PASSWORD - Registry credentials for pushing
+#
+# Build tool support:
+#   - docker + buildx: Multi-arch support with intelligent platform handling  
+#   - docker only: Single architecture fallback
+
+set -euo pipefail
+
+# make git available
+if ! [ -x "$(command -v git)" ]; then
+  echo "Installing git ..."
+  yum install -y git
+fi
+
+# Check if docker is available
+if ! [ -x "$(command -v docker)" ]; then
+  echo "Error: Docker is not available"
+  exit 1
+fi
+
+echo "Using docker for container builds"
+# Check if buildx is available for multi-arch builds
+if docker buildx version >/dev/null 2>&1; then
+  echo "Docker buildx is available for multi-arch builds"
+  DOCKER_BUILDX=true
+else
+  echo "Docker buildx not available, falling back to single-arch builds"
+  DOCKER_BUILDX=false
+fi
+
+
+if [ -z "${REPOSITORY:-}" ]; then
+  echo "Error: REPOSITORY environment variable is required"
+  exit 1
+fi
+repository=$REPOSITORY
+architectures=${ARCHITECTURES:-"amd64 arm64"}
+
+# when building locally, just tag with the current HEAD hash.
+version="$(git rev-parse --short HEAD)"
+branchName=""
+
+# deduce the tag from the Prow job metadata
+if [ -n "${PULL_BASE_REF:-}" ]; then
+  version="$(git tag --list "$PULL_BASE_REF")"
+
+  if [ -z "$version" ]; then
+    # if the base ref did not point to a tag, it's a branch name
+    version="$(git rev-parse --short "$PULL_BASE_REF")"
+    branchName="$PULL_BASE_REF"
+  else
+    # If PULL_BASE_REF is a tag, there is no branch available locally, plus
+    # there is no guarantee that vX.Y.Z is tagged _only_ in the release-X.Y
+    # branch; because of this we have to deduce the branch name from the tag
+    branchName="$(echo "$version" | sed -E 's/^v([0-9]+)\.([0-9]+)\..*/release-\1.\2/')"
+  fi
+fi
+
+# Prefix with "pr-" if not on a tag or branch
+if [ -n "${PULL_NUMBER:-}" ]; then
+  version="pr-$PULL_NUMBER-$version"
+  repository="$repository-prs"
+fi
+
+image="$repository:$version"
+echo "Building container image $image ..."
+
+# Function to build images with docker buildx
+build_with_docker_buildx() {
+  echo "Building multi-arch image $image ..."
+  
+  # Create platforms string for buildx
+  platforms=""
+  for arch in $architectures; do
+    if [ -n "$platforms" ]; then
+      platforms="$platforms,linux/$arch"
+    else
+      platforms="linux/$arch"
+    fi
+  done
+  
+  # For push builds, use multi-platform; for local builds, build per arch
+  if [ -z "${DRY_RUN:-}" ]; then
+    # Building for push - use multi-platform with --push
+    docker buildx build \
+      --file Dockerfile \
+      --tag "$image" \
+      --platform "$platforms" \
+      --build-arg "TARGETOS=linux" \
+      --push \
+      .
+  else
+    # For local/dry-run builds, build each architecture separately with --load
+    for arch in $architectures; do
+      fullTag="$image-$arch"
+      echo "Building $fullTag ..."
+      docker buildx build \
+        --file Dockerfile \
+        --tag "$fullTag" \
+        --platform "linux/$arch" \
+        --build-arg "TARGETOS=linux" \
+        --build-arg "TARGETARCH=$arch" \
+        --load \
+        .
+    done
+    # Tag the first architecture as the main image for local use
+    first_arch=$(echo $architectures | cut -d' ' -f1)
+    docker tag "$image-$first_arch" "$image"
+  fi
+}
+
+# Function to build images with regular docker (single arch only)
+build_with_docker() {
+  # Use only the first architecture for regular docker
+  arch=$(echo $architectures | cut -d' ' -f1)
+  fullTag="$image-$arch"
+  
+  echo "Building single-arch image $fullTag (docker without buildx) ..."
+  docker build \
+    --file Dockerfile \
+    --tag "$fullTag" \
+    --platform "linux/$arch" \
+    --build-arg "TARGETOS=linux" \
+    --build-arg "TARGETARCH=$arch" \
+    .
+    
+  # Tag it as the main image too
+  docker tag "$fullTag" "$image"
+}
+
+# Build images based on available docker features
+if [ "$DOCKER_BUILDX" = true ]; then
+  build_with_docker_buildx
+else
+  build_with_docker
+fi
+
+# Additionally to an image tagged with the Git tag, we also
+# release images tagged with the current branch name, which
+# is somewhere between a blanket "latest" tag and a specific
+# tag.
+if [ -n "$branchName" ] && [ -z "${PULL_NUMBER:-}" ]; then
+  branchImage="$repository:$branchName"
+
+  if [ "$DOCKER_BUILDX" = true ]; then
+    echo "Tagging multi-arch image as $branchImage ..."
+    docker tag "$image" "$branchImage"
+  else
+    echo "Tagging single-arch image as $branchImage ..."
+    docker tag "$image" "$branchImage"
+  fi
+fi
+
+# push images, except in dry runs
+if [ -z "${DRY_RUN:-}" ]; then
+  echo "Logging into GHCR ..."
+  
+  if [ "$DOCKER_BUILDX" = true ]; then
+    # buildx with --push already pushed during build
+    echo "Images already pushed during buildx build"
+  else
+    # Regular docker - need to login and push
+    if [ -n "${GHCR_USERNAME:-}" ] && [ -n "${GHCR_PASSWORD:-}" ]; then
+      echo "$GHCR_PASSWORD" | docker login ghcr.io -u "$GHCR_USERNAME" --password-stdin
+    else
+      echo "Skipping login (GHCR_USERNAME/GHCR_PASSWORD not provided)"
+    fi
+    
+    echo "Pushing images ..."
+    docker push "$image"
+
+    if [ -n "${branchImage:-}" ]; then
+      docker push "$branchImage"
+
+
+    fi
+  fi
+else
+  echo "Not pushing images because \$DRY_RUN is set."
+fi
+
+echo "Done."