Avoid warning on workflow_call triggers

Typically, we warn when there is no `push` trigger in the
workflow file that triggered this run. However, when this
action is triggered by a `workflow_call` event, we assume
there is a custom process for triggering the action and we
don't want to warn in this case.

src/workflow.ts

@@ -3,6 +3,7 @@ import * as path from "path";
 import zlib from "zlib";
 
 import * as core from "@actions/core";
+import * as github from "@actions/github";
 import * as yaml from "js-yaml";
 
 import * as api from "./api-client";
@@ -219,7 +220,12 @@ export async function getWorkflowErrors(
     }
   }
 
-  if (missingPush) {
+  // Avoid warning when there this action was triggered via workflow_call since
+  // the user has a custom workflow that is calling this action and we assume
+  // they know what they are doing.
+  const isWorkflowCall = github.context.eventName === "workflow_call"
+
+  if (missingPush && !isWorkflowCall) {
     errors.push(WorkflowErrors.MissingPushHook);
   }