Inject base path into manifest

Might fix #1181, although not for the reasons I initially
though (because the URLs are resolved from the manifest path, not the
path of the current page). This should ensure that the URLs used by the
manifest are always correct regardless of the manifest's path.

Author: code-asher

src/browser/media/manifest.json

@@ -1,12 +1,12 @@
 {
   "name": "code-server",
   "short_name": "code-server",
-  "start_url": "../../../..",
+  "start_url": "{{BASE}}",
   "display": "fullscreen",
   "background-color": "#fff",
   "description": "Run editors on a remote server.",
   "icons": [{
-    "src": "./code-server.png",
+    "src": "{{BASE}}/static-{{COMMIT}}/src/browser/media/code-server.png",
     "sizes": "384x384",
     "type": "image/png"
   }]

src/node/app/app.ts

@@ -24,7 +24,7 @@ export class MainHttpProvider extends HttpProvider {
     switch (route.base) {
       case "/static": {
         this.ensureMethod(request)
-        const response = await this.getResource(this.rootPath, route.requestPath)
+        const response = await this.getReplacedResource(route)
         if (!this.isDev) {
           response.cache = true
         }
@@ -75,6 +75,20 @@ export class MainHttpProvider extends HttpProvider {
     return this.getErrorRoot(route, "404", "404", "Application not found")
   }
 
+  /**
+   * Return a resource with variables replaced where necessary.
+   */
+  protected async getReplacedResource(route: Route): Promise<HttpResponse> {
+    if (route.requestPath.endsWith("/manifest.json")) {
+      const response = await this.getUtf8Resource(this.rootPath, route.requestPath)
+      response.content = response.content
+        .replace(/{{BASE}}/g, this.base(route))
+        .replace(/{{COMMIT}}/g, this.options.commit)
+      return response
+    }
+    return this.getResource(this.rootPath, route.requestPath)
+  }
+
   public async getRoot(route: Route): Promise<HttpResponse> {
     const recent = await this.api.recent()
     const apps = await this.api.installedApplications()