Improve completion of containers for docker rm

[albers]

- What I did
The cobra completion for docker rm completes all containers. This does not make much sense as not all containers are removable unless --force is given.
This PR aligns the completion to the legacy completion, where only removable containers are completed unless --force is given, see here.

- How I did it
Added a filter to the call of completion.ContainerNames that filters on container status and the value of --force.

- How to verify it

- Description for the changelog

Improve completion of containers for `docker rm`

@thaJeztah PTAL

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 3 lines in your changes missing coverage. Please review.

Project coverage is 60.67%. Comparing base (88f1e99) to head (147630a).
Report is 30 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5527      +/-   ##
==========================================
- Coverage   60.67%   60.67%   -0.01%     
==========================================
  Files         345      345              
  Lines       23488    23491       +3     
==========================================
  Hits        14252    14252              
- Misses       8263     8266       +3     
  Partials      973      973              

[laurazard]

This is totally fine for now, but I wish we had an enum (or whatever passes for one in Go) for the State.

[thaJeztah]

Ah, yes! I think I may have started working on a branch at some point, but need to dig it up. It's all a bit awkward as these parts are rather quirky, and these values are currently set in the container package, not in anything inside the api/xxx or client/xxx; https://github.com/moby/moby/blob/61030f0e87c8d893082599815897f10d440f9bda/container/state.go#L119-L158

// StateString returns a single string to describe state
func (s *State) StateString() string {
	if s.Running {
		if s.Paused {
			return "paused"
		}
		if s.Restarting {
			return "restarting"
		}
		return "running"
	}

	if s.RemovalInProgress {
		return "removing"
	}

	if s.Dead {
		return "dead"
	}

	if s.StartedAt.IsZero() {
		return "created"
	}

	return "exited"
}

// IsValidStateString checks if the provided string is a valid container state or not.
func IsValidStateString(s string) bool {
	if s != "paused" &&
		s != "restarting" &&
		s != "removing" &&
		s != "running" &&
		s != "dead" &&
		s != "created" &&
		s != "exited" {
		return false
	}
	return true
}

[thaJeztah]

I recall now that I also wanted to look at these completion helpers to allow passing filters so that the daemon would only return containers in specific state(s) to get the equivalent of;

docker ps --format='{{.Names}} {{.Status}}' --filter status=exited --filter status=created
container-1 created
container-2 exited
container-3 exited

(and perhaps add a != option for status to allow --filter status!=running)

[laurazard]

LGTM, thanks!

[thaJeztah]

LGTM, nice!!