A buildpack to run multiple buildpacks in sequence.
Unlike heroku-buildpack-multi, heroku-buildpack-compose combines the output of the release script of each child buildpack to produce the final output. Default targets and configuration variables defined by later buildpack take priority. Requirements are simply concatenated with no deduplication.
The contents of the config_vars key are added to the environment after each step and are visible when checking out and executing subsequent buildpacks.
By default heroku-buildpack-compose reads a list of buildpacks from a .buildpacks file in the root of the application repository. Buildpacks are described by the url of a git repository and spaced one per line. To read buildpacks from a different file, specify it's path (relative to the repository root) in the BUILDPACKS_FILE environment variable (Note: at present, passing configuration to buildpacks through environment variables requires the user-env-compile labs extension).
It is highly recommended that you use your own fork as updates may inadvertently break backwards compatibility and heroku provides no obvious way of versioning buildpacks.
This buildpack was intended to be used with the ssh buildpack to enable loading of buildpacks from private repositories. If there are any others I would be happy to list them here.
Please report any bugs to using the issue tracker.
Pull requests are welcome.