[ZEPPELIN-6404] Rewrite merge PR script in Python with no external dependencies

.claude/commands/merge-pr.md

@@ -0,0 +1,55 @@
+Merge a pull request using the Go CLI tool (`dev/merge-pr.go`).
+
+## Input
+
+User input: $ARGUMENTS
+
+This can be in any form — CLI flags, natural language, or a mix. Examples:
+- `5167`
+- `5167 fix-versions 0.13.0, also cherry-pick into branch-0.12`
+- `5167 --fix-versions 0.13.0 --release-branches branch-0.12`
+- `merge PR #5167 and resolve JIRA`
+
+Parse the user's intent and build the appropriate `go run dev/merge-pr.go` command.
+
+## Instructions
+
+1. Check if `go` is available by running `go version`. If not found:
+   - Detect OS and arch (`uname -s`, `uname -m`)
+   - Download Go to `.go/` directory: `curl -fsSL https://go.dev/dl/go1.23.6.<os>-<arch>.tar.gz | tar -xz -C .go --strip-components=1`
+   - Use `.go/bin/go` instead of `go` for all subsequent commands.
+   - `.go/` is already in `.gitignore`.
+2. Extract from the user input: PR number, fix-versions, release-branches, resolve-jira, and any other flags.
+3. If the PR number is missing or no arguments given, run `go run dev/merge-pr.go --help` to show available flags, then ask the user for the PR number and any options they want.
+4. Always add `--resolve-jira` unless the user explicitly says not to.
+5. Run a dry-run first:
+
+```
+go run dev/merge-pr.go --pr <number> --resolve-jira [--fix-versions <versions>] [--release-branches <branches>] --dry-run
+```
+
+6. Show the dry-run output (including the effective command) to the user and ask:
+   - Does the effective command look correct?
+   - Do you want to change fix-versions, add release-branches, or adjust anything?
+   - If the user wants changes, re-run dry-run with updated flags and ask again.
+   - If the user confirms, proceed to step 7.
+7. Run the actual merge command (without `--dry-run`), using the effective command from the dry-run output.
+8. After merge, verify the result and report back.
+
+## Flags Reference
+
+| Flag | Description |
+|------|-------------|
+| `--pr` | PR number (required) |
+| `--fix-versions` | JIRA fix version(s), comma-separated |
+| `--release-branches` | Release branch(es) to cherry-pick into, comma-separated |
+| `--resolve-jira` | Resolve associated JIRA issue(s) |
+| `--dry-run` | Show what would be done without making changes |
+| `--push-remote` | Git remote for pushing (default: apache) |
+| `--target` | Target branch (default: PR base branch) |
+
+## Notes
+
+- Always dry-run first. Never merge without user confirmation.
+- If `--fix-versions` is omitted and `--release-branches` is given, versions are auto-inferred from JIRA.
+- Tokens are read from environment: `GITHUB_OAUTH_KEY`, `JIRA_ACCESS_TOKEN`.

.gitignore

@@ -149,3 +149,6 @@ tramp
 
 # dotenv files
 .env
+
+# local Go installation
+.go/