Adds compare with branch command

Adds branches quick pick

src/quickPicks/branches.ts

@@ -0,0 +1,42 @@
+'use strict';
+import { QuickPickItem, QuickPickOptions, window } from 'vscode';
+import { GitBranch, GitUri } from '../gitService';
+import { CommandQuickPickItem, getQuickPickIgnoreFocusOut } from './quickPicks';
+import * as path from 'path';
+
+export class BranchQuickPickItem implements QuickPickItem {
+
+    label: string;
+    description: string;
+    detail: string;
+
+    constructor(public branch: GitBranch) {
+        this.label = `${branch.current ? '$(check)\u00a0' : '\u00a0\u00a0\u00a0\u00a0'} ${branch.name}`;
+        this.description = branch.remote ? '\u00a0\u00a0 remote branch' : null;
+    }
+}
+
+export class BranchesQuickPick {
+
+    static async show(branches: GitBranch[], uri: GitUri, goBackCommand?: CommandQuickPickItem): Promise<BranchQuickPickItem | CommandQuickPickItem | undefined> {
+
+        const items = branches.map(_ => new BranchQuickPickItem(_)) as (BranchQuickPickItem | CommandQuickPickItem)[];
+
+        if (goBackCommand) {
+            items.splice(0, 0, goBackCommand);
+        }
+
+        // const scope = await Keyboard.instance.beginScope({ left: goBackCommand });
+
+        const pick = await window.showQuickPick(items,
+            {
+                placeHolder: `Compare ${path.basename(uri.fsPath)} to \u2026`,
+                ignoreFocusOut: getQuickPickIgnoreFocusOut()
+            } as QuickPickOptions);
+        if (!pick) return undefined;
+
+        // await scope.dispose();
+
+        return pick;
+    }
+}