feat: add skip CI command support

Implement support for skip CI commands in commit messages to allow
users to skip PipelineRun execution. Supports [skip ci], [ci skip],
[skip tkn], and [tkn skip] commands.

When a skip command is detected in the commit message, PipelineRun
execution is skipped. However, GitOps commands (/test, /retest, etc.)
will still trigger PipelineRuns regardless of the skip command,
allowing users to manually trigger CI when needed.

Jira: https://issues.redhat.com/browse/SRVKP-8933

Signed-off-by: Akshay Pant <akshay.akshaypant@gmail.com>

Author: theakshaypant

README.md

@@ -65,6 +65,7 @@ Before getting started with Pipelines-as-Code, ensure you have:
 - **Multi-provider support**: Works with GitHub (via GitHub App & Webhook), GitLab, Gitea, Bitbucket Data Center & Cloud via webhooks.
 - **Annotation-driven workflows**: Target specific events, branches, or CEL expressions and gate untrusted PRs with `/ok-to-test` and `OWNERS`; see [Running the PipelineRun](https://pipelinesascode.com/docs/guide/running/).
 - **ChatOps style control**: `/test`, `/retest`, `/cancel`, and branch or tag selectors let you rerun or stop PipelineRuns from PR comments or commit messages; see [GitOps Commands](https://pipelinesascode.com/docs/guide/gitops_commands/).
+- **Skip CI support**: Use `[skip ci]`, `[ci skip]`, `[skip tkn]`, or `[tkn skip]` in commit messages to skip automatic PipelineRun execution for documentation updates or minor changes; GitOps commands can still override and trigger runs manually; see [Skip CI Commands](https://pipelinesascode.com/docs/guide/gitops_commands/#skip-ci-commands).
 - **Feedback**: GitHub Checks capture per-task timing, log snippets, and optional error annotations while redacting secrets; see [PipelineRun status](https://pipelinesascode.com/docs/guide/statuses/).
 - **Inline resolution**: The resolver bundles `.tekton/` resources, inlines remote tasks from Artifact Hub or Tekton Hub, and validates YAML before cluster submission; see [Resolver](https://pipelinesascode.com/docs/guide/resolver/).
 - **CLI**: `tkn pac` bootstraps installs, manages Repository CRDs, inspects logs, and resolves runs locally; see the [CLI guide](https://pipelinesascode.com/docs/guide/cli/).

docs/content/docs/guide/matchingevents.md

@@ -482,3 +482,94 @@ main and the branch called `release,nightly` you can do this:
 ```yaml
 pipelinesascode.tekton.dev/on-target-branch: [main, release,nightly]
 ```
+
+## Skip CI Commands
+
+Pipelines-as-Code supports skip commands in commit messages that allow you to skip
+PipelineRun execution for specific commits. This is useful when making documentation
+changes, minor fixes, or work-in-progress commits where running the full CI pipeline
+is unnecessary.
+
+### Supported Skip Commands
+
+You can include any of the following commands anywhere in your commit message to skip
+PipelineRun execution:
+
+* `[skip ci]` - Skip continuous integration
+* `[ci skip]` - Alternative format for skipping CI
+* `[skip tkn]` - Skip Tekton PipelineRuns
+* `[tkn skip]` - Alternative format for skipping Tekton
+
+**Note:** Skip commands are **case-sensitive** and must be in lowercase with brackets.
+
+### Example Usage
+
+```text
+docs: update README with installation instructions [skip ci]
+```
+
+or
+
+```text
+WIP: refactor authentication module
+
+This is still in progress and not ready for testing yet.
+
+[ci skip]
+```
+
+### How Skip Commands Work
+
+When a commit message contains a skip command:
+
+1. **Pull Requests**: No PipelineRuns will be created when the PR is opened or updated and HEAD commit contains skip command.
+2. **Push Events**: No PipelineRuns will be created when pushing to a branch with that commit message
+
+### GitOps Commands Override Skip CI
+
+**Important:** Skip CI commands can be overridden by using GitOps commands. Even if
+a commit contains a skip command like `[skip ci]`, you can still manually trigger
+PipelineRuns using:
+
+* `/test` - Trigger all matching PipelineRuns
+* `/test <pipelinerun-name>` - Trigger a specific PipelineRun
+* `/retest` - Retrigger failed PipelineRuns
+* `/retest <pipelinerun-name>` - Retrigger a specific PipelineRun
+* `/ok-to-test` - Allow running CI for external contributors
+* `/custom-comment` - Trigger PipelineRun having on-comment annotation
+
+This allows you to skip automatic CI execution while still maintaining the ability
+to manually trigger builds when needed.
+
+### Example: Skipping CI Then Manually Triggering
+
+```bash
+# Initial commit with skip command
+git commit -m "docs: update contributing guide [skip ci]"
+git push origin my-feature-branch
+# No PipelineRuns are created automatically
+
+# Later, you can manually trigger CI by commenting on the PR:
+# /test
+# This will create PipelineRuns despite the [skip ci] command
+```
+
+### Examples of When to Use Skip Commands
+
+Skip commands are useful for:
+
+* Documentation-only changes
+* README updates
+* Comment or formatting changes
+* Work-in-progress commits
+* Minor typo fixes
+* Configuration file updates that don't affect code
+
+### Examples of When NOT to Use Skip Commands
+
+Avoid using skip commands for:
+
+* Code changes that affect functionality
+* Changes to CI/CD pipeline definitions
+* Dependency updates
+* Any changes that should be tested before merging

pkg/adapter/sinker.go

@@ -3,10 +3,12 @@ package adapter
 import (
 	"bytes"
 	"context"
+	"fmt"
 	"net/http"
 
 	"github.com/openshift-pipelines/pipelines-as-code/pkg/apis/pipelinesascode/v1alpha1"
 	"github.com/openshift-pipelines/pipelines-as-code/pkg/kubeinteraction"
+	"github.com/openshift-pipelines/pipelines-as-code/pkg/matcher"
 	"github.com/openshift-pipelines/pipelines-as-code/pkg/params"
 	"github.com/openshift-pipelines/pipelines-as-code/pkg/params/info"
 	"github.com/openshift-pipelines/pipelines-as-code/pkg/pipelineascode"
@@ -69,8 +71,78 @@ func (s *sinker) processEvent(ctx context.Context, request *http.Request) error
 		if err := s.processEventPayload(ctx, request); err != nil {
 			return err
 		}
+
+		// For ALL events: Setup authenticated client early (including token scoping)
+		// This centralizes client setup and token scoping in one place for all event types
+		repo, err := s.findMatchingRepository(ctx)
+		if err != nil {
+			// Continue with normal flow - repository matching will be handled in matchRepoPR
+			s.logger.Debugf("Could not find matching repository for early client setup: %v", err)
+		} else {
+			// We found the repository, now setup client with token scoping
+			// If setup fails here, it's a configuration error and we should fail fast
+			if err := s.setupClient(ctx, repo); err != nil {
+				return fmt.Errorf("client setup failed: %w", err)
+			}
+			s.logger.Debugf("Client setup completed early in sinker for event type: %s", s.event.EventType)
+		}
+
+		// For PUSH events: commit message is already in event.SHATitle from the webhook payload
+		// We can check immediately without any API calls or repository lookups
+		if s.event.EventType == "push" && provider.SkipCI(s.event.SHATitle) {
+			s.logger.Infof("CI skipped for push event: commit %s contains skip command in message", s.event.SHA)
+			return nil
+		}
+
+		// For PULL REQUEST events: commit message needs to be fetched via API
+		// Get commit info for skip-CI detection (only if we successfully set up client above)
+		if s.event.EventType == "pull_request" && repo != nil {
+			// Get commit info (including commit message) via API
+			if err := s.vcx.GetCommitInfo(ctx, s.event); err != nil {
+				return fmt.Errorf("could not get commit info: %w", err)
+			}
+			// Check for skip-ci commands in pull request events
+			if s.event.HasSkipCommand {
+				s.logger.Infof("CI skipped for pull request event: commit %s contains skip command in message", s.event.SHA)
+				return nil
+			}
+		}
 	}
 
 	p := pipelineascode.NewPacs(s.event, s.vcx, s.run, s.pacInfo, s.kint, s.logger, s.globalRepo)
 	return p.Run(ctx)
 }
+
+// findMatchingRepository finds the Repository CR that matches the event.
+// This is a lightweight lookup to get credentials for early skip-ci checks.
+// Uses the canonical matcher implementation to avoid code duplication.
+func (s *sinker) findMatchingRepository(ctx context.Context) (*v1alpha1.Repository, error) {
+	// Use canonical matcher to find repository (empty string searches all namespaces)
+	repo, err := matcher.MatchEventURLRepo(ctx, s.run, s.event, "")
+	if err != nil {
+		return nil, fmt.Errorf("failed to match repository: %w", err)
+	}
+	if repo == nil {
+		return nil, fmt.Errorf("no repository found matching URL: %s", s.event.URL)
+	}
+
+	return repo, nil
+}
+
+// setupClient sets up the authenticated client with token scoping for ALL event types.
+// This is the primary location where client setup and GitHub App token scoping happens.
+// Centralizing this here ensures consistent behavior across all events and enables early
+// optimizations like skip-CI detection before expensive processing.
+func (s *sinker) setupClient(ctx context.Context, repo *v1alpha1.Repository) error {
+	return pipelineascode.SetupAuthenticatedClient(
+		ctx,
+		s.vcx,
+		s.kint,
+		s.run,
+		s.event,
+		repo,
+		s.globalRepo,
+		s.pacInfo,
+		s.logger,
+	)
+}