Improve heuristic for XML/TypeScript (#3883)

The heuristic for XML .ts files might match TypeScript generics
starting with TS

lib/linguist/heuristics.rb

@@ -477,7 +477,7 @@ module Linguist
     end
 
     disambiguate ".ts" do |data|
-      if data.include?("<TS")
+      if /<TS\b/.match(data)
         Language["XML"]
       else
         Language["TypeScript"]

samples/TypeScript/cache.ts

@@ -0,0 +1,102 @@
+import { DocumentNode } from 'graphql';
+import { getFragmentQueryDocument } from 'apollo-utilities';
+
+import { DataProxy, Cache } from './types';
+
+export type Transaction<T> = (c: ApolloCache<T>) => void;
+
+export abstract class ApolloCache<TSerialized> implements DataProxy {
+  // required to implement
+  // core API
+  public abstract read<T>(query: Cache.ReadOptions): T;
+  public abstract write(write: Cache.WriteOptions): void;
+  public abstract diff<T>(query: Cache.DiffOptions): Cache.DiffResult<T>;
+  public abstract watch(watch: Cache.WatchOptions): () => void;
+  public abstract evict(query: Cache.EvictOptions): Cache.EvictionResult;
+  public abstract reset(): Promise<void>;
+
+  // intializer / offline / ssr API
+  /**
+   * Replaces existing state in the cache (if any) with the values expressed by
+   * `serializedState`.
+   *
+   * Called when hydrating a cache (server side rendering, or offline storage),
+   * and also (potentially) during hot reloads.
+   */
+  public abstract restore(
+    serializedState: TSerialized,
+  ): ApolloCache<TSerialized>;
+
+  /**
+   * Exposes the cache's complete state, in a serializable format for later restoration.
+   */
+  public abstract extract(optimistic: boolean): TSerialized;
+
+  // optimistic API
+  public abstract removeOptimistic(id: string): void;
+
+  // transactional API
+  public abstract performTransaction(
+    transaction: Transaction<TSerialized>,
+  ): void;
+  public abstract recordOptimisticTransaction(
+    transaction: Transaction<TSerialized>,
+    id: string,
+  ): void;
+
+  // optional API
+  public transformDocument(document: DocumentNode): DocumentNode {
+    return document;
+  }
+  // experimental
+  public transformForLink(document: DocumentNode): DocumentNode {
+    return document;
+  }
+
+  // DataProxy API
+  /**
+   *
+   * @param options
+   * @param optimistic
+   */
+  public readQuery<QueryType>(
+    options: DataProxy.Query,
+    optimistic: boolean = false,
+  ): QueryType {
+    return this.read({
+      query: options.query,
+      variables: options.variables,
+      optimistic,
+    });
+  }
+
+  public readFragment<FragmentType>(
+    options: DataProxy.Fragment,
+    optimistic: boolean = false,
+  ): FragmentType | null {
+    return this.read({
+      query: getFragmentQueryDocument(options.fragment, options.fragmentName),
+      variables: options.variables,
+      rootId: options.id,
+      optimistic,
+    });
+  }
+
+  public writeQuery(options: Cache.WriteQueryOptions): void {
+    this.write({
+      dataId: 'ROOT_QUERY',
+      result: options.data,
+      query: options.query,
+      variables: options.variables,
+    });
+  }
+
+  public writeFragment(options: Cache.WriteFragmentOptions): void {
+    this.write({
+      dataId: options.id,
+      result: options.data,
+      variables: options.variables,
+      query: getFragmentQueryDocument(options.fragment, options.fragmentName),
+    });
+  }
+}