Introduce a "prune" package in which we maintain a list of prune
functions that are registered. Known prune "content-types" are
included in a pre-defined order, after which additional content
can be registered.
Using this approach no longer requires the "RunPrune" functions
to be exported, and allows additional content-types to be
introduced without having to import those packages into the
system package, so keeping things more decoupled.
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This patch adds a new builder subcommand, allowing to add more builder-related
commands in the future. Unfortunately `build` expects an argument so could not
be used as a subcommand.
This also implements `docker builder prune`, which is needed to prune the builder
cache manually without having to call `docker system prune`.
Today when relying on the legacy builder, users are able to prune dangling images
(used as build cache) by running `docker image prune`. This patch allows the
same usecase with buildkit.
Signed-off-by: Tibor Vass <tibor@docker.com>
