chore: import upstream snapshot with attribution

.github/workflows/gitnexus-pr-command.yml

@@ -0,0 +1,141 @@
+# Responds to `/gitnexus index` comments on pull requests.
+#
+# Gated to the same author_association roles (OWNER, MEMBER, COLLABORATOR)
+# as the automatic PR index trigger, but applied to the COMMENTER, not
+# the PR author. This intentionally lets a contributor index a PR from
+# a non-contributor / first-time fork author — the contributor takes
+# responsibility for the trust boundary by typing the command.
+#
+# When a matching comment lands on a PR, this workflow dispatches
+# `gitnexus-index.yml` with the PR number and the `refs/pull/<N>/head`
+# ref so indexing works for fork PRs too (GitHub mirrors every PR's
+# head ref into the base repo regardless of which fork it originated
+# from, so actions/checkout can always resolve it).
+#
+# Use cases:
+#   - Re-index a PR after a rebase without pushing a new commit
+#   - Index a docs-only PR that was skipped by paths-ignore
+#   - Index a non-contributor (fork) PR that the auto-trigger skipped
+#   - Re-run a failed index
+#
+# Supported commands:
+#   /gitnexus index             — index the PR with embeddings (default)
+#   /gitnexus index embeddings  — explicit form of the above; same effect
+#   /gitnexus index fast        — graph-only index (skip embeddings), for
+#                                 a quick re-index without waiting ~5 min
+#                                 of embedding generation
+
+name: GitNexus PR Command
+
+on:
+  issue_comment:
+    types: [created]
+
+permissions:
+  contents: read
+  pull-requests: write
+  actions: write # needed to dispatch gitnexus-index.yml
+
+concurrency:
+  group: gitnexus-pr-command-${{ github.event.issue.number }}
+  cancel-in-progress: false
+
+jobs:
+  dispatch:
+    # Only run for PR comments that start with /gitnexus from trusted
+    # commenters. Intentionally checks the COMMENTER's association so a
+    # contributor can index a non-contributor's PR on demand.
+    if: |
+      github.event.issue.pull_request != null &&
+      startsWith(github.event.comment.body, '/gitnexus') &&
+      (github.event.comment.author_association == 'OWNER' ||
+       github.event.comment.author_association == 'MEMBER' ||
+       github.event.comment.author_association == 'COLLABORATOR')
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - name: Parse command and resolve PR head ref
+        id: parse
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const body = context.payload.comment.body.trim();
+            const match = body.match(/^\/gitnexus\s+(\w+)(?:\s+(\w+))?/);
+            if (!match) {
+              core.setFailed(`Unrecognized command: ${body}. Try: /gitnexus index [fast]`);
+              return;
+            }
+            const [, subcommand, modifier] = match;
+            if (subcommand !== 'index') {
+              core.setFailed(`Unknown subcommand: ${subcommand}. Only 'index' is supported.`);
+              return;
+            }
+            // Default to embeddings on — a contributor typing the command
+            // has already decided they want a full re-index. The `fast`
+            // modifier is the explicit opt-out for graph-only runs.
+            // `embeddings` is accepted as a no-op alias for backwards
+            // compat with the previous command form.
+            let embeddings = 'true';
+            if (modifier === 'fast' || modifier === 'graph-only' || modifier === 'no-embeddings') {
+              embeddings = 'false';
+            }
+
+            // Use refs/pull/<N>/head instead of the raw head SHA. GitHub
+            // mirrors every PR's head into the base repo as this ref, so
+            // actions/checkout can always resolve it — even for PRs from
+            // forks whose raw SHAs don't exist in the base repo.
+            const prNum = context.payload.issue.number;
+            core.setOutput('pr_number', String(prNum));
+            core.setOutput('pr_ref', `refs/pull/${prNum}/head`);
+            core.setOutput('embeddings', embeddings);
+            core.info(
+              `Dispatching index for PR #${prNum} at refs/pull/${prNum}/head (embeddings=${embeddings}, modifier=${modifier || '(none)'})`,
+            );
+
+      - name: Dispatch gitnexus-index workflow
+        uses: actions/github-script@v7
+        env:
+          EMBEDDINGS: ${{ steps.parse.outputs.embeddings }}
+          PR_NUMBER: ${{ steps.parse.outputs.pr_number }}
+          PR_REF: ${{ steps.parse.outputs.pr_ref }}
+        with:
+          script: |
+            const prNumber = process.env.PR_NUMBER || '';
+            const prRef = process.env.PR_REF || '';
+            const embeddings = process.env.EMBEDDINGS || 'false';
+            if (!/^[0-9]+$/.test(prNumber)) {
+              core.setFailed(`Invalid PR number: ${prNumber}`);
+              return;
+            }
+            if (prRef !== `refs/pull/${prNumber}/head`) {
+              core.setFailed(`Invalid PR ref: ${prRef}`);
+              return;
+            }
+            if (!['true', 'false'].includes(embeddings)) {
+              core.setFailed(`Invalid embeddings value: ${embeddings}`);
+              return;
+            }
+            await github.rest.actions.createWorkflowDispatch({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              workflow_id: 'gitnexus-index.yml',
+              ref: 'main',
+              inputs: {
+                pr_number: prNumber,
+                pr_ref: prRef,
+                embeddings,
+                force: 'false',
+                deploy_after: 'true',
+              },
+            });
+
+      - name: React to the comment
+        uses: actions/github-script@v7
+        with:
+          script: |
+            await github.rest.reactions.createForIssueComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              comment_id: context.payload.comment.id,
+              content: 'rocket',
+            });