Add setting to disable chat history variables

Author: roblourens

src/vs/workbench/contrib/chat/browser/contrib/chatInputEditorContrib.ts

@@ -15,6 +15,7 @@ import { CompletionContext, CompletionItem, CompletionItemKind, CompletionList }
 import { ITextModel } from 'vs/editor/common/model';
 import { ILanguageFeaturesService } from 'vs/editor/common/services/languageFeatures';
 import { localize } from 'vs/nls';
+import { IConfigurationService } from 'vs/platform/configuration/common/configuration';
 import { Registry } from 'vs/platform/registry/common/platform';
 import { inputPlaceholderForeground } from 'vs/platform/theme/common/colorRegistry';
 import { IThemeService } from 'vs/platform/theme/common/themeService';
@@ -357,6 +358,7 @@ class VariableCompletions extends Disposable {
 		@ILanguageFeaturesService private readonly languageFeaturesService: ILanguageFeaturesService,
 		@IChatWidgetService private readonly chatWidgetService: IChatWidgetService,
 		@IChatVariablesService private readonly chatVariablesService: IChatVariablesService,
+		@IConfigurationService private readonly configurationService: IConfigurationService,
 	) {
 		super();
 
@@ -389,13 +391,14 @@ class VariableCompletions extends Disposable {
 					.filter(isResponseVM);
 
 				// TODO@roblourens work out a real API for this- maybe it can be part of the two-step flow that @file will probably use
-				const historyItems = history.map((h, i): CompletionItem => ({
+				const historyVariablesEnabled = this.configurationService.getValue('chat.experimental.historyVariables');
+				const historyItems = historyVariablesEnabled ? history.map((h, i): CompletionItem => ({
 					label: `@response:${i + 1}`,
 					detail: h.response.asString(),
 					insertText: `@response:${String(i + 1).padStart(String(history.length).length, '0')} `,
 					kind: CompletionItemKind.Text,
 					range: { insert, replace },
-				}));
+				})) : [];
 
 				const variableItems = Array.from(this.chatVariablesService.getVariables()).map(v => {
 					const withAt = `@${v.name}`;