Register code to the Debian alternatives system

Fixes #3541

build/gulpfile.vscode.js

@@ -289,7 +289,11 @@ function prepareDebPackage(arch) {
 					.pipe(es.through(function (f) { that.emit('data', f); }, function () { that.emit('end'); }));
 			}));
 
-		var all = es.merge(control, desktop, icon, shortcut, code);
+		var prerm = gulp.src('resources/linux/debian/prerm.template', { base: '.' })
+			.pipe(replace('@@NAME@@', product.applicationName))
+			.pipe(rename('DEBIAN/prerm'))
+
+		var all = es.merge(control, prerm, desktop, icon, shortcut, code);
 
 		// Register an apt repository if this is an official build
 		if (product.updateUrl && product.quality) {
@@ -300,6 +304,11 @@ function prepareDebPackage(arch) {
 				.pipe(replace('@@ARCHITECTURE@@', debArch))
 				.pipe(rename('DEBIAN/postinst'))
 			all = es.merge(all, postinst);
+		} else {
+			var postinst = gulp.src('resources/linux/debian/postinst.oss.template', { base: '.' })
+				.pipe(replace('@@NAME@@', product.applicationName))
+				.pipe(rename('DEBIAN/postinst'))
+			all = es.merge(all, postinst);
 		}
 
 		return all

resources/linux/debian/postinst.oss.template

+#!/usr/bin/env bash
+#
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for license information.
+
+# Register code in the alternatives system
+# Priority of 0 should never make code the default editor in auto mode as most
+# developers would prefer a terminal editor as the default.
+update-alternatives --install /usr/bin/editor editor /usr/bin/@@NAME@@ 0

resources/linux/debian/postinst.template

@@ -3,6 +3,12 @@
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License. See License.txt in the project root for license information.
 
+# Register code in the alternatives system
+# Priority of 0 should never make code the default editor in auto mode as most
+# developers would prefer a terminal editor as the default.
+update-alternatives --install /usr/bin/editor editor /usr/bin/@@NAME@@ 0
+
+# Register repository as an apt source
 get_apt_config_value() {
 	echo $(apt-config dump | grep "$1 " | sed -e "s/$1 \"//" -e "s/\";$//")
 }

resources/linux/debian/prerm.template

+#!/usr/bin/env bash
+#
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for license information.
+
+# Deregister code from the alternatives system
+update-alternatives --remove editor /usr/bin/@@NAME@@
\ No newline at end of file