v3 fish completions suggest already selected command for L2+ commands

[bittrance]

My urfave/cli version is

c6c5804

Checklist

• Are you running the latest v3 release? The list of releases is here.
• Did you check the manual for your release? The v3 manual is here
• Did you perform a search about this problem? Here's the GitHub guide about searching.

Describe the bug

L1 commands get a condition saying there should not be any commands present. L2 commands only say that their parent should be present and so will suggest the same subcommand again.

To reproduce

	app := &cli.Command{
		Name:                  "mycli",
		Version:               "1.0.0",
		Usage:                 "Pure awesomeness.",
		EnableShellCompletion: true,
		Suggest:               true,
		Commands: []*cli.Command{
			{
				Name:  "more-awesome",
				Usage: "Become awesomer!",
				Action: func(ctx context.Context, cmd *cli.Command) error {
					return nil
				},
				Commands: []*cli.Command{
					{
						Name:  "set",
						Usage: "Set new awesomeness.",
					},
				},
			},
		},
	}

Observed behavior

Set is suggested even though we are already "at" set.

[13:44] mycli more-awesome set <tab>
h     (Shows a list of commands or help for one command)  set  (Set new awesomeness.)
help  (Shows a list of commands or help for one command)

Expected behavior

Want only relevant subcommands.

Want to fix this yourself?

In order to address this, completions that are siblings should have a negative condition on the list of siblings, sort of like saying "only one of these commands should be completed". PR pending.

Run go version and paste its output here

go version go1.23.8 linux/amd64

Run go env and paste its output here

GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/home/andqvi/.cache/go-build'
GOENV='/home/andqvi/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/andqvi/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='linux'
GOPATH='/home/andqvi/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/home/andqvi/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.23.8.linux-amd64'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/home/andqvi/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.23.8.linux-amd64/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.23.8'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/home/andqvi/.config/go/telemetry'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/home/andqvi/projects/external/harness-cli/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build320049062=/tmp/go-build -gno-record-gcc-switches'