Create a README.md

Author: rujche

README.md

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+# App Modernization Skills
+
+This repo is the **single source of truth** for Java app modernization skill files. Changes here are automatically synced to downstream repos via GitHub Actions.
+
+## Downstream Repos
+
+| Repo | Description |
+|------|-------------|
+| [Extension repo](https://github.com/devdiv-azure-service-dmitryr/azure-java-migration-copilot-vscode-extension) | VS Code extension for Java migration |
+| [CLI repo](https://github.com/devdiv-azure-service-dmitryr/modernize-cli) | Modernize CLI tool |
+
+## Repo Structure
+
+```
+skills/                  # Skill files (source of truth)
+skill-mapping.csv        # Maps skill files to downstream repo paths
+scripts/sync-skills.sh   # Sync script used by GitHub Actions
+.github/workflows/       # GitHub Actions workflow
+```
+
+## How It Works
+
+1. Edit skill files under `skills/`.
+2. On push to `main`, the GitHub Actions workflow reads `skill-mapping.csv` row by row and syncs each skill file to the downstream repos.
+3. The workflow creates a PR in each downstream repo with the updated content.
+
+Key behaviors:
+- **Front matter is preserved** — each downstream repo keeps its own front matter; only the body content is replaced.
+- **Skill comments are stripped** — blocks wrapped in `/~~ ... ~/` are not synced to downstream repos. Use these for internal notes.
+
+## Skill File Format
+
+Each skill file lives in `skills/` with its own front matter:
+
+```md
+---
+name: Migrate Oracle to PostgreSQL
+description: Migrate Oracle Database to PostgreSQL database in a Java project
+---
+
+Skill content here...
+```
+
+### Skill Comments
+
+Use the `/~~ ... ~/` block to add comments that will **not** be synced downstream:
+
+```md
+/~~
+~ This comment will not appear in downstream repos.
+~/
+```
+
+## Skill Mapping
+
+The `skill-mapping.csv` file maps each skill to its path in the downstream repos:
+
+```csv
+skill file path,extension repo kb file path,CLI repo skill file path
+oracle-to-postgresql.md,kb/database-tasks/oracle-to-postgresql.md,src/.../SKILL.md
+```
+
+When adding a new skill, add a row to this CSV with the corresponding downstream paths.
+
+## GitHub Actions
+
+The sync workflow can be triggered:
+
+- **Automatically** — on any push to `main` that modifies `skills/**` or `skill-mapping.csv`.
+- **Manually** — via workflow dispatch with the following parameters:
+  - **skill_branch** — Skill repo branch to sync from (default: `main`).
+  - **extension_repo_branch** — Extension repo branch to sync into (default: `main`). Set to empty string to skip.
+  - **cli_repo_branch** — CLI repo branch to sync into (default: `main`). Set to empty string to skip.
+
+### Prerequisites
+
+A repository secret `DOWNSTREAM_REPO_PAT` must be configured with a GitHub Personal Access Token that has write access to both downstream repos.