This allows alternative plugins - such as dokku-letsencrypt - to inject scheduled cron tasks into the cron system used by Dokku. Cron systems can choose to include or not include a cron task based on the specified scheduler, and can also optionally use a third parameter to store arbitrary information.
This change minimizes the work needed to be done when tagging images. It edits the image manifest directly only when necessary, allowing restarts of an app to avoid having an extra layer.
This also additionally allows to deploy images with ONBUILD directives without running the ONBUILD directives.
Lastly, users building docker images that run Dokku will need to use a new sudoer wrapper for the `docker-image-labeler` binary to work correctly. A reference version has been placed in the `docker` skeleton directory.
Closes#3931
Refs #4226
The default for an app is empty, meaning it will fallback to the global value (which defaults to true). This will allow users to properly override the global value, regardless of what it is.
This functionality enables users to manage a global crontab for the Dokku user that contains all scheduled tasks across all apps. Alternative schedulers can implement cron tasks as desired.
0.22.0 changed allowed values for app names, making it more difficult for users to fix their app names - you need to either downgrade+rename or recreate the app. The `apps:rename` command can now rename these old applications to the new standard.
Also drop some app name verification from internal commands. Duplicate verification doesn't help much, and though it isn't excessively slow, it does prevent us from running commands against old apps that exist.
Refs #4267
When setting the `--app` flag, there was a special case for the config plugin. This plugin used to take the `--no-restart` flag as the first argument - and still did until this change - resulting in an invalid call to the plugin subcommands. What is worse is that this functionality carried over to all other plugins as they were rewritten in golang, and thus the issue spread without us knowing.
The fix is to support GNU flag parsing rules, which Golang does not do by default (Because Of Reasons™). Switching to `github.com/spf13/pflag` fixes this issue, and also allows positional arguments to be placed wherever, even in the middle of flags.
Closes#4255
