Add getRepositoryNwo() helper functions

src/repository.ts

@@ -1,4 +1,4 @@
-import { ConfigurationError } from "./util";
+import { ConfigurationError, getRequiredEnvParam } from "./util";
 
 // A repository name with owner, parsed into its two parts
 export interface RepositoryNwo {
@@ -6,6 +6,36 @@ export interface RepositoryNwo {
   repo: string;
 }
 
+/**
+ * Get the repository name with owner from the environment variable
+ * `GITHUB_REPOSITORY`.
+ *
+ * @returns The repository name with owner.
+ */
+export function getRepositoryNwo(): RepositoryNwo {
+  return getRepositoryNwoFromEnv("GITHUB_REPOSITORY");
+}
+
+/**
+ * Get the repository name with owner from the first environment variable that
+ * is set and non-empty.
+ *
+ * @param envVarNames The names of the environment variables to check.
+ * @returns The repository name with owner.
+ * @throws ConfigurationError if none of the environment variables are set.
+ */
+export function getRepositoryNwoFromEnv(
+  ...envVarNames: string[]
+): RepositoryNwo {
+  const envVarName = envVarNames.find((name) => process.env[name]);
+  if (!envVarName) {
+    throw new ConfigurationError(
+      `None of the env vars ${envVarNames.join(", ")} are set`,
+    );
+  }
+  return parseRepositoryNwo(getRequiredEnvParam(envVarName));
+}
+
 export function parseRepositoryNwo(input: string): RepositoryNwo {
   const parts = input.split("/");
   if (parts.length !== 2) {