feat: (unstable) set x-github-delivery header on requests sent in r…

…esponse to webhook event (#367)

src/webhooks.ts

@@ -27,7 +27,7 @@ export function webhooks(
 
         return {
           ...event,
-          octokit: octokit,
+          octokit,
         };
       }
 
@@ -49,9 +49,19 @@ export function webhooks(
         },
       })) as Octokit;
 
+      // set `x-github-delivery` header on all requests sent in response to the current
+      // event. This allows GitHub Support to correlate the request with the event.
+      // This is not documented and not considered public API, the header may change.
+      // Once we document this as best practice on https://docs.github.com/en/rest/guides/best-practices-for-integrators
+      // we will make it official
+      /* istanbul ignore next */
+      octokit.hook.before("request", (options) => {
+        options.headers["x-github-delivery"] = event.id;
+      });
+
       return {
         ...event,
-        octokit: octokit,
+        octokit,
       };
     },
   });