Helpfully mention assets:clobber in UPGRADING.md

UPGRADING.md

@@ -43,7 +43,7 @@ module.exports = {
 
 **The 'link_tree' directive added to 'app/assets/manifest.js'**
 
-This tells Sprockets to include the files in `app/assets/builds` during `assets:precompile`. This is the folder where `yarn build` will place the bundled files, so make sure you commit it to the repository and don't delete it when cleaning assets. 
+This tells Sprockets to include the files in `app/assets/builds` during `assets:precompile`. This is the folder where `yarn build` will place the bundled files, so make sure you commit it to the repository and don't delete it when cleaning assets.
 
 **What about babel?**
 
@@ -167,7 +167,7 @@ Now that the CSS files will be placed into `app/assets/build`, Sprockets no long
 
 ### Configuring multiple entrypoints
 
-Sprockets will only compile files in the root directories listed in `manifest.js`, but the sass package that `yarn build` uses will also check subfolders, which might cause compilation errors if your scss files are using features like `@import` and variables. This means that if you have multiple entry points in your app, you have some extra work ahead of you. 
+Sprockets will only compile files in the root directories listed in `manifest.js`, but the sass package that `yarn build` uses will also check subfolders, which might cause compilation errors if your scss files are using features like `@import` and variables. This means that if you have multiple entry points in your app, you have some extra work ahead of you.
 
 Let's assume you have the following structure in your `app/asset/stylesheets` folder:
 
@@ -242,11 +242,11 @@ background: image_url('hero.jpg')
 
 Using the same path with `url` in Propshaft will cause it to raise an error, saying it cannot locate `theme/hero.jpg`. That's because Propshaft assumes all paths are relative to the path of the file it's processing. Since it was processing a css file inside the `theme` folder, it will also look for `hero.jpg` in the same folder.
 
-By adding a `/` at the start of the path we are telling Propshaft to consider this path as an absolute path. While this change in behavior increases the work a bit when upgrading, it makes **external libraries like FontAwesome and Bootstrap themes work out-of-the-box**.  
+By adding a `/` at the start of the path we are telling Propshaft to consider this path as an absolute path. While this change in behavior increases the work a bit when upgrading, it makes **external libraries like FontAwesome and Bootstrap themes work out-of-the-box**.
 
 ### Asset content
 
-It's a common pattern in apps to inline small SVG files and low resolution versions of images that need to be displayed as quickly as possible. In Propshaft, the same line of code works for all environments: 
+It's a common pattern in apps to inline small SVG files and low resolution versions of images that need to be displayed as quickly as possible. In Propshaft, the same line of code works for all environments:
 ```ruby
 Rails.application.assets.load_path.find('logo.svg').content
 ```
@@ -261,6 +261,6 @@ raw Rails.application.assets.load_path.find('logo.svg').content
 
 Propshaft uses a dynamic assets resolver in development mode. However, when you run `assets:precompile` locally Propshaft will then switch to a static assets resolver. Therefore, changes to assets will not be observed anymore and you will have to precompile the assets each time changes are made. This is different to Sprockets.
 
-If you wish to have dynamic assets resolver enabled again, you need to clean your target folder (usually `public/assets`) and propshaft will start serving dynamic content from source.
+If you wish to have dynamic assets resolver enabled again, you need to clean your target folder (usually `public/assets`) and propshaft will start serving dynamic content from source. One way to do this is to run `rails assets:clobber`.
 
 Another way to watch changes in your CSS & JS assets is by running `bin/dev` command instead of `rails server` that not only runs the server but also keeps looking for any changes in the assets and once it detects any changes, it compiles them while the server is running. This is possible because of the `Procfile.dev`.