fix: support fork PR intent comments - #205
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July 27, 2026 10:02
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Pull request overview
This PR updates Mainline’s PR intent comment pipeline to safely support fork-based pull requests by shifting the GitHub Actions workflow to pull_request_target and adding an engine/CLI pathway that reads fork-published intent metadata as Git data without importing it into upstream state.
Changes:
- Added
PRCommentWithOptionsand CLI flags (--pr,--fork-url) to render fork actor-log intent metadata in PR comments without syncing/importing. - Introduced fork intent discovery + rendering (including provenance messaging) and added targeted engine/CLI tests for fork behavior.
- Migrated the
Mainline PR Intentworkflow to a singlepull_request_targetflow with concurrency cancellation and stale-head checks.
Reviewed changes
Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.
Show a summary per file
| File | Description |
|---|---|
| internal/engine/pr.go | Adds PullRequestCommentOptions + fork-aware PR comment rendering entrypoint. |
| internal/engine/pr_fork.go | Implements fork actor-log discovery/fetch and merges fork intents into PR comment view. |
| internal/engine/pr_fork_test.go | Adds regression tests ensuring fork intent preview doesn’t import/accept upstream state and filters terminal intents. |
| internal/cli/pr.go | Wires new pr-comment options (--pr, --fork-url) to the engine options struct. |
| internal/cli/root_test.go | Ensures new pr-comment flags are registered. |
| .github/workflows/mainline-pr-intent.yml | Switches to pull_request_target, adds concurrency, stale event checks, and fork-safe checkout/fetch strategy. |
Comments suppressed due to low confidence (3)
internal/engine/pr_fork.go:121
- Similarly, decoding failures for specific fork event payloads (sealed/abandoned/superseded) currently abort the entire PR comment generation. Since these payloads are also untrusted, treat decode failures as a skip for that event instead of failing the run.
case domain.EventIntentSealed:
var event domain.IntentSealedEvent
if err := json.Unmarshal(raw, &event); err != nil {
return nil, domain.NewError(
domain.ErrInvalidInput,
fmt.Sprintf("fork sealed event %s is invalid: %v", base.EventID, err),
)
}
internal/engine/pr_fork.go:133
- For fork PR previews, an invalid abandoned event payload should not fail the entire PR intent comment generation (untrusted fork input). Skip malformed abandoned events instead.
case domain.EventIntentAbandoned:
var event domain.IntentAbandonedEvent
if err := json.Unmarshal(raw, &event); err != nil {
return nil, domain.NewError(
domain.ErrInvalidInput,
fmt.Sprintf("fork abandoned event %s is invalid: %v", base.EventID, err),
)
}
internal/engine/pr_fork.go:145
- For fork PR previews, an invalid superseded event payload should not fail the entire PR intent comment generation (untrusted fork input). Skip malformed superseded events instead.
case domain.EventIntentSuperseded:
var event domain.IntentSupersededEvent
if err := json.Unmarshal(raw, &event); err != nil {
return nil, domain.NewError(
domain.ErrInvalidInput,
fmt.Sprintf("fork superseded event %s is invalid: %v", base.EventID, err),
)
}
Comment on lines
+214
to
+219
| func forkPRCommentImportRef(actorID string, prNumber int) string { | ||
| if prNumber > 0 { | ||
| return fmt.Sprintf("refs/mainline/imports/pr-comments/pr-%d/%s/log", prNumber, actorID) | ||
| } | ||
| return "refs/mainline/imports/pr-comments/manual/" + actorID + "/log" | ||
| } |
Comment on lines
+100
to
+108
| intents := make(map[string]domain.IntentView) | ||
| for index, raw := range rawEvents { | ||
| var base domain.BaseEvent | ||
| if err := json.Unmarshal(raw, &base); err != nil { | ||
| return nil, domain.NewError( | ||
| domain.ErrInvalidInput, | ||
| fmt.Sprintf("fork actor log event %d is not valid JSON: %v", index, err), | ||
| ) | ||
| } |
Comment on lines
+82
to
+86
| with: | ||
| ref: ${{ github.event.pull_request.base.sha }} | ||
| fetch-depth: 0 | ||
| persist-credentials: false | ||
|
|
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Mainline Intent
Intent:
int_807c5590Status:
proposedTitle: 为 Mainline PR Intent Action 增加 fork PR 支持
What changed
将 Mainline PR Intent workflow 迁移为单一 pull_request_target 路径：同仓 PR 继续 checkout 并执行 head 代码，fork PR 只 checkout 可信 base，并把 PR head 作为 Git 数据读取。pr-comment 新增可选的 fork URL/PR 参数，可从 fork actor refs 临时投影 contributor-published intents，复用原有 commit-range、多 intent、branch fallback、marker 和 sticky comment 行为。加入并发取消、head 新鲜度校验、live PR body 检查和临时 ref 清理，并补充 engine/CLI 回归测试。
Why
普通 pull_request 在 fork PR 上只有只读 token，无法写评论；直接移除同仓限制又会让高权限 job 执行不可信 fork 代码。新的可信 base 执行路径在不改变现有同仓评论能力的前提下安全读取 fork intent metadata，并避免在 review 阶段导入或修改 upstream Mainline 状态。
Decisions
Subsystems: .github, cli, engine, github-actions, pull-request, intent-rendering, fork-actor-log