cli/command/completion: add FromList utility

It's an alias for cobra.FixedCompletions but takes a variadic list
of strings, so that it's not needed to construct an array for this.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
(cherry picked from commit 5e7bcbeac6)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/command/completion/functions.go

@@ -130,6 +130,11 @@ func EnvVarNames(_ *cobra.Command, _ []string, _ string) (names []string, _ cobr
 	return names, cobra.ShellCompDirectiveNoFileComp
 }
 
+// FromList offers completion for the given list of options.
+func FromList(options ...string) ValidArgsFn {
+	return cobra.FixedCompletions(options, cobra.ShellCompDirectiveNoFileComp)
+}
+
 // FileNames is a convenience function to use [cobra.ShellCompDirectiveDefault],
 // which indicates to let the shell perform its default behavior after
 // completions have been provided.

cli/command/container/run.go

@@ -72,6 +72,7 @@ func NewRunCommand(dockerCli command.Cli) *cobra.Command {
 	_ = cmd.RegisterFlagCompletionFunc("env", completion.EnvVarNames)
 	_ = cmd.RegisterFlagCompletionFunc("env-file", completion.FileNames)
 	_ = cmd.RegisterFlagCompletionFunc("network", completion.NetworkNames(dockerCli))
+	_ = cmd.RegisterFlagCompletionFunc("pull", completion.FromList(PullImageAlways, PullImageMissing, PullImageNever))
 	return cmd
 }
 

cmd/docker/completions.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"github.com/docker/cli/cli/command/completion"
 	"github.com/docker/cli/cli/context/store"
 	"github.com/spf13/cobra"
 )
@@ -19,13 +20,7 @@ func registerCompletionFuncForGlobalFlags(contextStore store.Store, cmd *cobra.C
 	if err != nil {
 		return err
 	}
-	err = cmd.RegisterFlagCompletionFunc(
-		"log-level",
-		func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
-			values := []string{"debug", "info", "warn", "error", "fatal"}
-			return values, cobra.ShellCompDirectiveNoFileComp
-		},
-	)
+	err = cmd.RegisterFlagCompletionFunc("log-level", completion.FromList("debug", "info", "warn", "error", "fatal"))
 	if err != nil {
 		return err
 	}