ref: elaborate on resource value resolution

contributing.md

@@ -193,7 +193,8 @@ The main files you will be working with are:
 - Adding an asset (image, icon, stylesheet, translation file and misc. other files):
   1. Add the asset to the `assets` folder in the root of the project, under the correct subfolder
   2. Add the asset to the [`assets/resources.json`](./assets/resources.json) file by following the format of the other entries.  
-    If the path begins with a slash, it will start at the project root (where package.json is), otherwise it will start at the `assets` folder.
+    If the path begins with a slash, it will start at the project root (where package.json is), otherwise it will start at the `assets` folder.  
+    The path string or all values in the object of each resource will be passed through the function `resolveResourceVal()` in [`src/tools/post-build.ts`](./src/tools/post-build.ts) to resolve placeholders like `$BRANCH`. View all replacements by looking up that function.
   3. The asset will be immediately available in the userscript after the next build and the `@resource` directive will automatically point at the locally served asset or the GitHub CDN, depending on the build mode.
   4. **When committing, make sure to commit the assets first, then rebuild the userscript and make a second commit.**  
     This needs to be done because the build script at `src/tools/post-build.ts` will use the *previous* commit hash to create version-independent URLs for the assets. These will continue to work in the future, instead of pointing to an ever-changing branch where files could be moved, renamed or deleted at any time.

src/tools/post-build.ts

@@ -254,8 +254,8 @@ async function exists(path: string) {
 }
 
 /** Resolves the value of an entry in resources.json */
-function resolveVal(value: string, buildNbr: string) {
-  if(!value.includes("$"))
+function resolveResourceVal(value: string, buildNbr: string) {
+  if(!(/\$/.test(value)))
     return value;
 
   const replacements = [
@@ -284,8 +284,8 @@ async function getResourceDirectives(ref: string) {
         ? await getFileHashSha256(pathVal.replace(/\?.+/g, ""))
         : undefined;
       resourcesHashed[name] = typeof val === "object"
-        ? { path: resolveVal(val.path, ref), ref: resolveVal(val.ref, ref), hash }
-        : { path: getResourceUrl(resolveVal(val, ref), ref), ref, hash };
+        ? { path: resolveResourceVal(val.path, ref), ref: resolveResourceVal(val.ref, ref), hash }
+        : { path: getResourceUrl(resolveResourceVal(val, ref), ref), ref, hash };
     }
 
     const addResourceHashed = async (name: string, path: string, ref: string) => {