ci: add label-based trigger for release PR gates workflow with draft protection (#1887)

This change adds the ability to easily queue the release version of PR
gates using GitHub labels, while preserving the original draft PR
protection behavior.

## Problem

The OpenVMM repository has a release version of PR gates
(`openvmm-pr-release.yaml`) that runs the same checks as regular PR
gates but compiled in release mode. This workflow was only triggerable
manually via `workflow_dispatch`, making it cumbersome for maintainers
to queue when needed.

## Solution

Added label-based triggering to the release PR gates workflow with
proper safeguards. Now maintainers can simply add the
`run-release-gates` label to any non-draft PR to automatically trigger
the release version of the gates.

## Changes

### Workflow Triggers
The release PR workflow now responds to:
- **Manual trigger**: `workflow_dispatch` (preserved for backward
compatibility)
- **Label trigger**: `pull_request` with `types: [labeled]` on main and
release branches

### Conditional Execution
All jobs include a condition to only run when both requirements are met:
```yaml
if: contains(github.event.pull_request.labels.*.name, 'run-release-gates') && github.event.pull_request.draft == false
```

### Draft Protection
Unlike the initial implementation, this preserves the original draft PR
gating behavior. The workflow will only run when:
- The specific `run-release-gates` label is present **AND**
- The PR is not in draft status

### Code Changes
- Modified `flowey/flowey_hvlite/src/pipelines/checkin_gates.rs` to add
PR triggers for the `PrRelease` configuration
- Added conditional logic using `gh_dangerous_override_if` to check for
both the required label and draft status
- Updated documentation in the coding conventions guide

## Usage

1. Developer creates a PR
2. Maintainer adds the `run-release-gates` label when release testing is
needed
3. GitHub automatically triggers the release gates workflow (only if PR
is not draft)
4. All tests run in release mode and report results back to the PR

## Technical Notes

The implementation uses GitHub's standard approach for label-based
triggering (`types: [labeled]` + job-level filtering) as GitHub Actions
doesn't provide a way to trigger workflows on specific labels directly.
This is the same pattern used by major open-source projects and follows
GitHub's documented best practices.

## Benefits

- **Easy to use**: Simple one-click label addition
- **Controlled access**: Only maintainers can add labels to PRs
- **Automatic**: No need to manually navigate to GitHub Actions
- **Selective**: Only runs when specifically requested
- **Protected**: Maintains draft PR protection behavior
- **Efficient**: Workflow starts for any label but immediately skips
jobs if conditions aren't met
- **Backward compatible**: Manual trigger still works, regular PR
workflow unchanged

Fixes #1560.

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Co-authored-by: benhillis <[email protected]>
Co-authored-by: Ben Hillis <[email protected]>

Author: 3 people

.github/workflows/openvmm-pr-release.yaml

@@ -443,3 +443,38 @@ goes more in-depth as to why.
 
 Instead, name things based on what they logically provide, like functionality or
 data types.
+
+## Release Gates Workflow
+
+_Triggered Manually:_ **Yes** (via GitHub labels)
+
+In addition to the standard PR gates that run in debug mode, OpenVMM also provides
+a "Release Gates" workflow that runs the same checks but compiled in release mode.
+This workflow takes significantly longer to run but can catch issues that only
+manifest in optimized builds.
+
+### When to Use Release Gates
+
+The release gates workflow should be used when:
+
+- Making changes to performance-critical code paths
+- Modifying compiler flags or build configuration
+- Implementing low-level optimizations
+- Debugging issues that only appear in release builds
+- Before merging large refactoring changes
+
+### How to Trigger Release Gates
+
+To run the release gates on your PR:
+
+1. Ensure your PR is ready for review (not in draft mode)
+2. Add the `release-ci-required` label to your PR
+3. The workflow will automatically trigger and run all checks in release mode
+
+The workflow will only run when the specific label is present, so you have full
+control over when to use this more resource-intensive testing.
+
+### Label Management
+
+Only repository maintainers can add labels to PRs. If you need release gates
+run on your PR, ask a maintainer to add the `release-ci-required` label for you.

Guide/src/dev_guide/contrib/code.md

@@ -85,8 +85,15 @@ impl IntoPipeline for CheckinGatesCli {
                         .gh_set_name("[flowey] OpenVMM PR");
                 }
                 PipelineConfig::PrRelease => {
-                    // This workflow is triggered manually.
-                    pipeline.gh_set_name("[flowey] OpenVMM Release PR");
+                    // This workflow is triggered when a specific label is added to a PR.
+                    pipeline
+                        .gh_set_pr_triggers(GhPrTriggers {
+                            branches,
+                            types: vec!["labeled".into()],
+                            auto_cancel: false,
+                            exclude_branches: vec![],
+                        })
+                        .gh_set_name("[flowey] OpenVMM Release PR");
                 }
             }
         }
@@ -116,7 +123,8 @@ impl IntoPipeline for CheckinGatesCli {
         )?;
 
         pipeline.inject_all_jobs_with(move |job| {
-            job.dep_on(&cfg_common_params)
+            let mut job = job
+                .dep_on(&cfg_common_params)
                 .dep_on(|_| flowey_lib_hvlite::_jobs::cfg_versions::Request {})
                 .dep_on(
                     |_| flowey_lib_hvlite::_jobs::cfg_hvlite_reposource::Params {
@@ -130,7 +138,16 @@ impl IntoPipeline for CheckinGatesCli {
                 .gh_grant_permissions::<flowey_lib_common::gh_task_azure_login::Node>([(
                     GhPermission::IdToken,
                     GhPermissionValue::Write,
-                )])
+                )]);
+
+            // For the release pipeline, only run if the "release-ci-required" label is present and PR is not draft
+            if matches!(config, PipelineConfig::PrRelease) {
+                job = job.gh_dangerous_override_if(
+                    "contains(github.event.pull_request.labels.*.name, 'release-ci-required') && github.event.pull_request.draft == false",
+                );
+            }
+
+            job
         });
 
         let openhcl_musl_target = |arch: CommonArch| -> Triple {