Adding a first claude slash command for syncing downstream with upstream

Signed-off-by: Matthias Wessendorf <[email protected]>

Author: matzew

.claude/commands/sync-downstream.md

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+---
+description: Sync downstream repo with upstream main, preserving downstream-specific files
+---
+
+Sync downstream repository with upstream changes while preserving downstream-specific files.
+
+# Important Instructions
+
+- **ALWAYS** start from a detached HEAD: `git checkout --detach`
+- **DO NOT** use TodoWrite tool
+- **DO NOT** ask for confirmations - just execute
+- **BE CONCISE** - minimal output, only show final summary
+
+# Execution Steps
+
+Execute these commands in sequence:
+
+```bash
+# 1. Start from detached HEAD (REQUIRED)
+git checkout --detach
+
+# 2. Delete old sync branch if it exists
+git branch -D sync-downstream 2>/dev/null || true
+
+# 3. Fetch and create sync branch
+git fetch downstream
+git fetch upstream
+git checkout -b sync-downstream upstream/main
+git merge -s ours --no-commit downstream/main
+
+# 4. Restore downstream files (read from .downstream-preserve or use defaults)
+git checkout downstream/main -- .ci-operator.yaml .snyk .tekton/ Dockerfile.ci Dockerfile.ocp Makefile-ocp.mk OWNERS mcp_config.toml renovate.json
+
+# 5. Update dependencies
+go mod tidy
+go mod vendor
+git add vendor/
+
+# 6. Commit everything in ONE commit
+git commit -am "sync: merge upstream main with downstream config"
+```
+
+# Output
+
+After completion, show ONLY:
+- Commit hash
+- File change summary: `git diff --stat downstream/main..HEAD | tail -1`
+- Next steps:
+  ```
+  git push origin sync-downstream
+  gh pr create --base downstream/main
+  ```
+
+# Error Handling
+
+If any command fails, stop immediately and show the error. No rollback needed - user can investigate.

.downstream-preserve

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+# Downstream files/folders to preserve during upstream sync
+# One entry per line, supports directories with trailing /
+.ci-operator.yaml
+.snyk
+.tekton/
+Dockerfile.ci
+Dockerfile.ocp
+Makefile-ocp.mk
+OWNERS
+mcp_config.toml
+renovate.json