Every time I deploy my Rails 3.2 project to Heroku, rake assets:precompile is run:
$ git push heroku master
...
----> Preparing app for Rai
This worked for me. manifest.yml did nothing for me on my rails 4 project.
https://gist.github.com/Geesu/d0b58488cfae51f361c6
Sure! You'll need to create a manifest.yml in your_app/pubilc/assets directory.
The file can be blank. But ideally, you precompile everything locally, so deploys to Heroku would be much faster.
Make sure that you also committed the manifest.yml file when you're pushing to Heroku. Something like git add -f your_app/pubilc/assets/manifest.yml and a git push heroku master should suffice.
In rails 4, create the file manifest-<md5 hash>.json instead of manifest.yml
Just precompile locally with rake assets: precompile, check in the resulting assets that are in public/assets, and push to heroku.
This will automatically create the manifest-.yml or json file in your public/assets directory; then heroku will detect that and report Detected manifest file, assuming assets were compiled locally.
Note 1: Some people have a line in development.rb that makes these go to public/dev-assets instead; if so, you need to rename dev-assets to just assets)
Note 2: Make sure your .gitignore file is not excluding the public/assets directory.