# Plan: Issue #125 — Rename GITEA_URL → VCS_URL

## Problem

The `GITEA_URL` environment variable (and `--gitea-url` flag) implies the binary only works with Gitea.
Now that review-bot supports both Gitea and GitHub/GHES, this name is misleading.
Renaming to `VCS_URL` makes the binary platform-agnostic in its interface.

## Constraints

- Must not break existing users who already use `GITEA_URL` — need a fallback
- The CLI flag `--gitea-url` should also be updated to `--vcs-url` for consistency
- `INTEGRATION_GITEA_URL` in integration tests is a test-only env var, not the binary's interface; but should be updated for clarity
- The action YAML uses `GITEA_URL` as an internal shell variable in bash scripts — distinct from the env var passed to the binary
- All changes must compile and pass existing tests

## Files Affected

### Binary / Go source
| File | Change |
|------|--------|
| `cmd/review-bot/main.go` | Rename `--gitea-url` → `--vcs-url`, add `VCS_URL` as primary, keep `GITEA_URL` fallback |
| `cmd/review-bot/integration_test.go` | Rename `INTEGRATION_GITEA_URL` → `INTEGRATION_VCS_URL` (test-only, no external compat concern) |
| `integration_test.go` | Same — rename `INTEGRATION_GITEA_URL` → `INTEGRATION_VCS_URL` |

### Action YAML
| File | Change |
|------|--------|
| `.gitea/actions/review/action.yml` | Rename input `gitea-url` → `vcs-url`; update env var passed to binary: `VCS_URL` instead of `GITEA_URL`; keep internal bash var as `GITEA_URL` (only used for release download, not passed to binary) |
| `.gitea/workflows/ci.yml` | Rename `GITEA_URL` env var to `VCS_URL` in Run review step |

### Documentation
| File | Change |
|------|--------|
| `README.md` | Update CLI example, env var table entry |

## Proposed Approach

### 1. Backward-compatible env var lookup in main.go

Replace:
```go
giteaURL := flag.String("gitea-url", envOrDefault("GITEA_URL", ""), "Gitea instance URL")
```

With:
```go
giteaURL := flag.String("vcs-url", envOrDefaultFallback("VCS_URL", "GITEA_URL", ""), "VCS server URL (e.g. https://gitea.example.com)")
```

Add a helper:
```go
// envOrDefaultFallback reads primary env var; if empty, falls back to deprecated env var.
func envOrDefaultFallback(primary, deprecated, defaultVal string) string {
    if v := os.Getenv(primary); v != "" {
        return v
    }
    if v := os.Getenv(deprecated); v != "" {
        slog.Warn("deprecated env var in use; rename to " + primary, "old", deprecated, "new", primary)
        return v
    }
    return defaultVal
}
```

**Note:** This must be called AFTER `setupLogger` conceptually, but the flag default is evaluated at flag registration time. Since `setupLogger` runs before `flag.Parse()`, the slog.Warn will print correctly at runtime. We use `log.Printf` as a fallback if this proves problematic.

Actually — flag defaults are evaluated at registration (line 57), before `setupLogger`. The warning won't go through slog. Two options:
- Use `log.Printf` for the deprecation warning (always visible)
- Move the fallback lookup to after `flag.Parse()`, checking if the parsed value is still empty

**Decision:** Move fallback to a post-parse check. This is cleaner:
```go
vcsURL := flag.String("vcs-url", os.Getenv("VCS_URL"), "VCS server URL")
flag.Parse()
// Backward compat: fall back to deprecated GITEA_URL
if *vcsURL == "" {
    if v := os.Getenv("GITEA_URL"); v != "" {
        slog.Warn("GITEA_URL is deprecated; use VCS_URL instead")
        *vcsURL = v
    }
}
```

This is clean, idiomatic, and the warning goes through slog correctly.

### 2. Keep `--gitea-url` as deprecated alias

Add a hidden flag for backward compat:
```go
giteaURLAlias := flag.String("gitea-url", "", "Deprecated: use --vcs-url")
```

Post-parse:
```go
if *vcsURL == "" && *giteaURLAlias != "" {
    slog.Warn("--gitea-url is deprecated; use --vcs-url instead")
    *vcsURL = *giteaURLAlias
}
```

### 3. Internal variable rename

Rename `giteaURL` local variable → `vcsURL` throughout `main.go` for consistency.

### 4. Error message update

```go
fmt.Fprintf(os.Stderr, "Required: --vcs-url, --repo, --pr, --reviewer-token, --llm-model\n")
```

### 5. Action YAML changes

In `.gitea/actions/review/action.yml`:
- Input `gitea-url` → `vcs-url` (with same description, `required: false`, `default: ''`)
- Line 172: `GITEA_URL: ${{ inputs.gitea-url || github.server_url }}` → `VCS_URL: ${{ inputs.vcs-url || github.server_url }}`
- Lines 115, 140: internal bash vars `GITEA_URL=` are used for downloading binaries — NOT passed to the review-bot binary. Leave them as internal bash vars (they're scope-local in bash). These could be renamed to `SERVER_URL` or `BASE_URL` for local clarity, but renaming them isn't strictly required.

In `.gitea/workflows/ci.yml`:
- Line 52: `GITEA_URL: ${{ github.server_url }}` → `VCS_URL: ${{ github.server_url }}`

### 6. Integration test updates

`INTEGRATION_GITEA_URL` → `INTEGRATION_VCS_URL` in both test files.

### 7. README

- CLI example: `--gitea-url` → `--vcs-url`
- Env var table: `GITEA_URL` → `VCS_URL`, add note about `GITEA_URL` fallback

## Backward Compatibility Summary

| Old | New | Fallback? |
|-----|-----|-----------|
| `GITEA_URL` env var | `VCS_URL` | ✅ with deprecation warning |
| `--gitea-url` flag | `--vcs-url` | ✅ with deprecation warning |
| `gitea-url` action input | `vcs-url` | ⚠️ No (action version bump handles this) |
| `INTEGRATION_GITEA_URL` | `INTEGRATION_VCS_URL` | N/A (test-only) |

## Error Cases

- Both `VCS_URL` and `GITEA_URL` set: `VCS_URL` wins (primary takes precedence)
- Both `--vcs-url` and `--gitea-url` provided: `--vcs-url` wins
- Neither set: existing "missing required flags" error unchanged

## Edge Cases

- `os.Getenv` returns "" for unset AND set-to-empty — consistent with existing behavior
- The `envOrDefault` helper is unchanged; we add `envOrDefaultFallback` for the one renamed var

## Testing Strategy

- Existing unit tests pass unchanged (they don't test env var parsing directly)
- Integration tests updated to use new env var name
- Manual: `GITEA_URL=https://example.com ./review-bot --repo x --pr 1 ...` should print deprecation warning and proceed
- Manual: `VCS_URL=https://example.com ./review-bot ...` should work silently

## Completion Checklist

1. `VCS_URL` is read first; `GITEA_URL` is fallback with deprecation warning
2. `--vcs-url` flag is primary; `--gitea-url` is deprecated alias with warning
3. Error message references `--vcs-url` not `--gitea-url`
4. `action.yml` passes `VCS_URL` (not `GITEA_URL`) to the binary
5. `ci.yml` passes `VCS_URL` (not `GITEA_URL`) to the binary
6. README updated in CLI example and env var table
7. Integration tests use `INTEGRATION_VCS_URL`
8. `go test ./...` passes
9. `go vet ./...` passes
10. `go build ./cmd/review-bot` succeeds

## Open Questions

- Should the CLI flag `--gitea-url` be completely hidden from `--help` or just deprecated with a note? The issue doesn't specify. Decision: keep it visible but add "(deprecated: use --vcs-url)" to the description.
- Should action.yml also add `gitea-url` as a deprecated input alias? The issue says "Update the action to pass the new env var name" — no mention of backward compat for the action input. Decision: rename only, no alias (action users pin a version anyway).
- The bash-internal `GITEA_URL` variable in action.yml scripts (used for release download, not passed to binary) — rename for clarity? Decision: yes, rename to `BASE_URL` to avoid confusion with the env var.