Update ci.yml to be dispatchable and skippable (woocommerce#45331)

Co-authored-by: Adrian Moldovan <3854374+adimoldovan@users.noreply.github.com>

.github/workflows/ci.yml

@@ -14,6 +14,12 @@ on:
         required: true
         default: 'default'
         type: string
+  workflow_dispatch:
+    inputs:
+      pr_simulate:
+        description: 'Would you like to run CI on a pull request? If so, enter the PR number here. If blank, the entire suite will be run.'
+        type: string
+        default: ''
 
 concurrency:
   group: '${{ github.workflow }}-${{ github.ref }}'
@@ -23,13 +29,46 @@ env:
   FORCE_COLOR: 1
 
 jobs:
+  dispatch-handler:
+    name: 'Handle dispatched workflow'
+    runs-on: 'ubuntu-20.04'
+    if: ${{ github.event_name == 'workflow_dispatch' && inputs.pr_simulate }}
+    outputs:
+      head: ${{ steps.pr-info.outputs.head }}
+      base: ${{ steps.pr-info.outputs.base }}
+
+    steps:
+      - uses: actions/github-script@v7
+        name: 'Grab PR info.'
+        id: 'pr-info'
+        env:
+          PR: ${{ inputs.pr_simulate }}
+        with:
+          retries: 3
+          script: |
+            if ( ! process.env.PR ) {
+              return;
+            }
+            const PR = await github.rest.pulls.get( {
+              pull_number: process.env.PR,
+              repo: context.repo.repo,
+              owner: context.repo.owner,
+            } );
+            core.setOutput( 'head', PR.data.head.ref );
+            core.setOutput( 'base', PR.data.base.ref );
   project-jobs:
     # Since this is a monorepo, not every pull request or change is going to impact every project.
     # Instead of running CI tasks on all projects indiscriminately, we use a command to detect
     # which projects have changed and what kind of change occurred. This lets us build the
     # matrices that we can use to run CI tasks only on the projects that need them.
     name: 'Build Project Jobs'
     runs-on: 'ubuntu-20.04'
+    needs: 'dispatch-handler'
+    # Because forks of this repository may want to skip running this CI automatically, but still
+    # be able to run it via workflow_dispatch, if the SKIP_CI variable is truthy, and we're not
+    # running from a workflow_dispatch, we'll skip generating the project matrix and any jobs.
+    # Because dispatch-handler may be skipped, we need the always() here.
+    if: ${{ always() && ( github.event_name == 'workflow_dispatch' || ! vars.SKIP_CI ) }}
     outputs:
       lint-jobs: ${{ steps.project-jobs.outputs.lint-jobs }}
       test-jobs: ${{ steps.project-jobs.outputs.test-jobs }}
@@ -39,16 +78,24 @@ jobs:
         name: 'Checkout'
         with:
           fetch-depth: 0
+          # If the workflow wasn't triggered by dispatch, this will be empty and use defaults.
+          ref: ${{ needs.dispatch-handler.outputs.head }}
+
       - uses: './.github/actions/setup-woocommerce-monorepo'
         name: 'Setup Monorepo'
         with:
           php-version: false # We don't want to waste time installing PHP since we aren't using it in this job.
+
       - uses: actions/github-script@v7
         name: 'Build Matrix'
         id: 'project-jobs'
+        env:
+          PR_SIM: ${{ needs.dispatch-handler.outputs.base }}
         with:
           script: |
-            let baseRef = ${{ toJson( github.base_ref ) }};
+            const prSim = process.env.PR_SIM;
+            
+            let baseRef = prSim || ${{ toJson( github.base_ref ) }};
             if ( baseRef ) {
               baseRef = `--base-ref origin/${ baseRef }`;
             }
@@ -71,23 +118,35 @@ jobs:
               githubEvent = trigger;
             }
             
+            // Override the event 'workflow_dispatch' event type if we're simulating a PR.
+            if ( prSim ) {
+              githubEvent = 'pull_request';
+            }
+            
             const child_process = require( 'node:child_process' );
             child_process.execSync( `pnpm utils ci-jobs ${ baseRef } --event ${ githubEvent }` );
-  
+
   project-lint-jobs:
     name: "Lint - ${{ matrix.projectName }} ${{ matrix.optional && ' (optional)' || ''}}"
     runs-on: 'ubuntu-20.04'
-    needs: 'project-jobs'
-    if: ${{ needs.project-jobs.outputs.lint-jobs != '[]' && github.event_name == 'pull_request' }}
+    needs: [
+      'project-jobs',
+      'dispatch-handler'
+    ]
+    # Because dispatch-handler may be skipped, we need the always() here.
+    if: ${{ always() && needs.project-jobs.outputs.lint-jobs != '[]' && ( github.event_name == 'pull_request' || inputs.pr_simulate != '' ) }}
     strategy:
       fail-fast: false
       matrix:
         include: ${{ fromJSON( needs.project-jobs.outputs.lint-jobs ) }}
+
     steps:
       - uses: 'actions/checkout@v4'
         name: 'Checkout'
         with:
           fetch-depth: 0
+          # If the workflow wasn't triggered by dispatch, this will be empty and use defaults.
+          ref: ${{ needs.dispatch-handler.outputs.head }}
 
       - uses: './.github/actions/setup-woocommerce-monorepo'
         name: 'Setup Monorepo'
@@ -97,20 +156,27 @@ jobs:
 
       - name: 'Lint'
         run: 'pnpm --filter="${{ matrix.projectName }}" ${{ matrix.command }}'
-  
+
   project-test-jobs:
     name: "${{ matrix.name }}"
     runs-on: 'ubuntu-20.04'
-    needs: 'project-jobs'
-    if: ${{ needs.project-jobs.outputs.test-jobs != '[]' }}
+    needs: [
+      'project-jobs',
+      'dispatch-handler'
+    ]
+    if: ${{ always() && needs.project-jobs.outputs.test-jobs != '[]' }}
     env: ${{ matrix.testEnv.envVars }}
     strategy:
       fail-fast: false
       matrix:
         include: ${{ fromJSON( needs.project-jobs.outputs.test-jobs ) }}
+
     steps:
       - uses: 'actions/checkout@v4'
         name: 'Checkout'
+        with:
+          # If the workflow wasn't triggered by dispatch, this will be empty and use defaults.
+          ref: ${{ needs.dispatch-handler.outputs.head }}
 
       - uses: './.github/actions/setup-woocommerce-monorepo'
         name: 'Install Monorepo'
@@ -233,7 +299,7 @@ jobs:
         'project-lint-jobs',
         'project-test-jobs',
       ]
-    if: ${{ always() && github.event_name != 'pull_request'  }}
+    if: ${{ always() && github.event_name != 'pull_request' && ! github.event.pull_request.head.repo.fork }}
     steps:
       - uses: 'actions/checkout@v4'
         name: 'Checkout'
@@ -270,7 +336,7 @@ jobs:
         'project-jobs',
         'project-test-jobs',
       ]
-    if: ${{ always() && needs.project-jobs.outputs.report-jobs != '[]' }}
+    if: ${{ always() && needs.project-jobs.outputs.report-jobs != '[]' && ! github.event.pull_request.head.repo.fork }}
     strategy:
       fail-fast: false
       matrix:
@@ -324,7 +390,7 @@ jobs:
             -f suite="$REPORT_NAME" \
             -f report_title="$REPORT_TITLE" \
             --repo woocommerce/woocommerce-test-reports
-  
+
   report-flaky-tests:
     name: 'Create issues for flaky tests'
     if: ${{ !cancelled() && ! github.event.pull_request.head.repo.fork }}