fix: Improve values.yaml update mechanism with sed instead of awk

Replace complex awk-based parsing with simpler sed-based approach for updating
Docker image tags in values.yaml. The previous awk logic had issues detecting
changes properly.

Changes:
- Use sed for both WordPress and Nginx tag replacements (more reliable)
- Simplify version extraction using sed and cut commands
- Fix backfile creation to avoid overwriting during edits
- Add debug output showing current and new versions
- Improve error handling in diff command (redirect stderr)

The sed approach:
1. Matches the image section (wordpress: or nginx:)
2. Performs substitution until the next top-level key
3. Directly replaces the entire tag value with quotes

This ensures:
- Correct YAML structure preservation
- Reliable change detection
- Accurate version comparison for Chart.yaml update decision

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

.gitea/workflows/image-update-and-release.yaml

@@ -159,47 +159,31 @@ jobs:
           cp values.yaml values.yaml.bak
 
           # 現在のWordPressバージョンを取得（Chart.yamlの更新判定用）
-          CURRENT_WP_VERSION=$(grep -A 3 'wordpress:' values.yaml.bak | grep 'tag:' | awk -F'"' '{print $2}')
+          CURRENT_WP_VERSION=$(grep -A 1 'wordpress:' values.yaml | grep 'tag:' | sed 's/.*tag: "\([^-]*\).*/\1/')
-          NEW_WP_VERSION="${{ steps.wordpress.outputs.version }}"
+          NEW_WP_VERSION=$(echo "${{ steps.wordpress.outputs.version }}" | cut -d'-' -f1)
+
+          # 変更前のバージョンを表示
+          CURRENT_NGINX=$(grep -A 1 'nginx:' values.yaml | grep 'tag:' | sed 's/.*tag: "\(.*\)".*/\1/')
+          echo "Current versions:"
+          echo "  WordPress: $CURRENT_WP_VERSION"
+          echo "  Nginx: $CURRENT_NGINX"
+          echo "New versions:"
+          echo "  WordPress: $NEW_WP_VERSION"
+          echo "  Nginx: ${{ steps.nginx.outputs.version }}"
 
           # WordPressのtagを更新
-          # image.wordpress.tagの行を特定して置換
+          sed -i "/^  wordpress:/,/^  [a-z]/s|tag: \"[^\"]*\"|tag: \"${{ steps.wordpress.outputs.version }}\"|" values.yaml
-          awk -v new_tag="${{ steps.wordpress.outputs.version }}" '
-          /^image:/ { in_image=1 }
-          in_image && /^  wordpress:/ { in_wordpress=1; print; next }
-          in_wordpress && /^    tag:/ {
-            print "    tag: \"" new_tag "\""
-            in_wordpress=0
-            next
-          }
-          in_wordpress && /^  [a-z]/ { in_wordpress=0 }
-          in_image && /^[a-z]/ { in_image=0 }
-          { print }
-          ' values.yaml.bak > values.yaml.tmp
-          mv values.yaml.tmp values.yaml
 
           # Nginxのtagを更新
-          cp values.yaml values.yaml.tmp
+          sed -i "/^  nginx:/,/^  [a-z]/s|tag: \"[^\"]*\"|tag: \"${{ steps.nginx.outputs.version }}\"|" values.yaml
-          awk -v new_tag="${{ steps.nginx.outputs.version }}" '
-          /^image:/ { in_image=1 }
-          in_image && /^  nginx:/ { in_nginx=1; print; next }
-          in_nginx && /^    tag:/ {
-            print "    tag: \"" new_tag "\""
-            in_nginx=0
-            next
-          }
-          in_nginx && /^  [a-z]/ { in_nginx=0 }
-          in_image && /^[a-z]/ { in_image=0 }
-          { print }
-          ' values.yaml.tmp > values.yaml
-          rm values.yaml.tmp
 
           # 変更内容を表示
+          echo ""
           echo "=== Changes in values.yaml ==="
           diff values.yaml.bak values.yaml || true
 
           # 実際に変更されたか確認
-          if diff -q values.yaml.bak values.yaml > /dev/null; then
+          if diff -q values.yaml.bak values.yaml > /dev/null 2>&1; then
             echo "INFO: No changes were made to values.yaml (versions already up to date)"
             cat values.yaml | grep -A 5 "image:"
             echo "chart_version_update_needed=false" >> $GITHUB_OUTPUT
@@ -216,8 +200,9 @@ jobs:
             fi
           fi
 
+          echo ""
           echo "=== Updated values.yaml (image section) ==="
-          grep -A 10 "^image:" values.yaml
+          grep -A 5 "^image:" values.yaml
 
       - name: Increment chart version
         if: steps.update_values.outputs.chart_version_update_needed == 'true'