system prune: refactor to use "register" functions

[thaJeztah]

system prune: use register function for prune functions

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.

system prune: delegate confirmation message and validation

This adds a "dry-run" / "pre-check" option for prune-functions,
which delegates constructing the confirmation message (what is
about to be pruned) and validation of the given options to the
prune-functions.

This helps separating concerns, and doesn't enforce knowledge
about what's supported by each content-type onto the system
prune command.

system prune: delegate version check

Move the version-check for pruners to the pruner, which can
return a ErrNotImplemented error to indicate they won't
be run with the API version that's used.

This helps separating concerns, and doesn't enforce knowledge
about what's supported by each content-type onto the system
prune command.

cli/command: remove exported "RunPrune" functions

These are no longer used, and unlikely to be used externally.

- Human readable description for the release notes

Go SDK: cli/command/builder: remove `CachePrune()`, which was no longer used.
Go SDK: cli/command/container: remove `RunPrune()`, which was no longer used.
Go SDK: cli/command/image: remove `RunPrune()`, which was no longer used.
Go SDK: cli/command/network: remove `RunPrune()`, which was no longer used.
Go SDK: cli/command/volume: remove `RunPrune()`, which was no longer used.

- A picture of a cute animal (not mandatory but encouraged)

[thaJeztah]

Interesting; bad test?

#18 65.69 === Failed
#18 65.69 === FAIL: cli/command/container TestRunCommandWithContentTrustErrors (unknown)
#18 65.69 panic: Fail in goroutine after TestRunPullTermination has completed
#18 65.69 
#18 65.69 goroutine 317 [running]:
#18 65.69 testing.(*common).Fail(0xc0001b7180)
#18 65.69 	/usr/local/go/src/testing/testing.go:988 +0xcb
#18 65.69 testing.(*common).FailNow(0xc0001b7180)
#18 65.69 	/usr/local/go/src/testing/testing.go:1017 +0x26
#18 65.69 github.com/docker/cli/vendor/gotest.tools/v3/assert.NilError({0x1154ca8, 0xc0001b7180}, {0x114ade0, 0x18b8df0}, {0x0, 0x0, 0x0})
#18 65.69 	/go/src/github.com/docker/cli/vendor/gotest.tools/v3/assert/assert.go:177 +0xee
#18 65.69 github.com/docker/cli/cli/command/container.TestRunPullTermination.func3.2()
#18 65.69 	/go/src/github.com/docker/cli/cli/command/container/run_test.go:254 +0x1a5
#18 65.69 created by github.com/docker/cli/cli/command/container.TestRunPullTermination.func3 in goroutine 316
#18 65.69 	/go/src/github.com/docker/cli/cli/command/container/run_test.go:246 +0x10c
#18 65.69 
#18 65.69 === FAIL: cli/command/container TestRunCommandWithContentTrustErrors/offline-notary-server (unknown)
#18 65.69 panic: Fail in goroutine after TestRunPullTermination has completed
#18 65.69 
#18 65.69 goroutine 317 [running]:
#18 65.69 testing.(*common).Fail(0xc0001b7180)
#18 65.69 	/usr/local/go/src/testing/testing.go:988 +0xcb
#18 65.69 testing.(*common).FailNow(0xc0001b7180)
#18 65.69 	/usr/local/go/src/testing/testing.go:1017 +0x26
#18 65.69 github.com/docker/cli/vendor/gotest.tools/v3/assert.NilError({0x1154ca8, 0xc0001b7180}, {0x114ade0, 0x18b8df0}, {0x0, 0x0, 0x0})
#18 65.69 	/go/src/github.com/docker/cli/vendor/gotest.tools/v3/assert/assert.go:177 +0xee
#18 65.69 github.com/docker/cli/cli/command/container.TestRunPullTermination.func3.2()
#18 65.69 	/go/src/github.com/docker/cli/cli/command/container/run_test.go:254 +0x1a5
#18 65.69 created by github.com/docker/cli/cli/command/container.TestRunPullTermination.func3 in goroutine 316
#18 65.69 	/go/src/github.com/docker/cli/cli/command/container/run_test.go:246 +0x10c

[thaJeztah]

We should probably rewrite these tests to use mockups for these (to be looked at in a follow-up).

[Copilot]

Pull Request Overview

This PR refactors the system prune functionality to use a registration-based approach instead of directly importing and calling prune functions from different packages. The changes introduce a new pruner package that maintains a registry of prune functions, allowing for better decoupling and separation of concerns.

• Introduces a pruner package with registration system for prune functions
• Delegates confirmation message generation and validation to individual pruners
• Moves API version checks to individual pruners rather than centralized logic
• Removes exported RunPrune functions that are no longer needed

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

File	Description
cli/command/system/pruner/pruner.go	New package defining the pruner registry system and interfaces
cli/command/system/prune.go	Refactored to use the new pruner registry instead of direct imports
cli/command/{volume,network,image,container,builder}/prune.go	Updated to register prune functions and replace exported RunPrune with internal pruneFn
cli/command/system/prune_test.go	Added imports to ensure pruners are registered for tests

[Benehiko]

LGTM, I couldn't see anything obvious in the PR that could be problematic.

[thaJeztah]

@vvoland have time to give this a second pair of eyes?