Add isPRFile404 (#20)

Author: yakov116

index.ts

@@ -186,6 +186,7 @@ collect.set('isPRCommit', [
 ]);
 
 export const isPRCommit404 = (): boolean => isPRCommit() && document.title.startsWith('Commit range not found · Pull Request');
+export const isPRFile404 = (): boolean => isPRFiles() && document.title.startsWith('Commit range not found · Pull Request');
 
 export const isPRConversation = (url: URL | Location = location): boolean => /^pull\/\d+$/.test(getRepoPath(url)!);
 collect.set('isPRConversation', [

test.ts

@@ -111,6 +111,16 @@ test('isPRCommit404', t => {
 	t.false(pageDetect.isPRCommit404());
 });
 
+test('isPRFile404', t => {
+	document.title = 'Commit range not found · Pull Request #789 · sindresorhus/eslint-plugin-unicorn';
+	location.href = 'https://github.com/sindresorhus/eslint-plugin-unicorn/pull/789/files/a58b37845f1b2660221de019e4ae6c736feedc26..eed168224d7994652b1d1ff69a5c8cebee223faf';
+	t.true(pageDetect.isPRFile404());
+
+	document.title = 'Add `align-repository-header` feature by fregante · Pull Request #3313 · sindresorhus/refined-github';
+	location.href = 'https://github.com/sindresorhus/refined-github/pull/3313/files/a14fb2c94eae3ca83a3a97688a171fcc3405524f..fbeeba9825f12b5ded9cd4bb04d5df4b0cf2f2a8';
+	t.false(pageDetect.isPRFile404());
+});
+
 test('getRepoPath', t => {
 	const pairs = new Map<string, string | undefined>([
 		[