Merge pull request #2344 from thaJeztah/19.03_backport_builder_prune_flags

[19.03 backport] fix builder prune flag descriptions
Upstream-commit: 7c803f7c3456efc19d5461f0918f834967bcf452
Component: cli

Author: thaJeztah

components/cli/cli/command/builder/prune.go

@@ -44,8 +44,8 @@ func NewPruneCommand(dockerCli command.Cli) *cobra.Command {
 
 	flags := cmd.Flags()
 	flags.BoolVarP(&options.force, "force", "f", false, "Do not prompt for confirmation")
-	flags.BoolVarP(&options.all, "all", "a", false, "Remove all unused images, not just dangling ones")
-	flags.Var(&options.filter, "filter", "Provide filter values (e.g. 'unused-for=24h')")
+	flags.BoolVarP(&options.all, "all", "a", false, "Remove all unused build cache, not just dangling ones")
+	flags.Var(&options.filter, "filter", "Provide filter values (e.g. 'until=24h')")
 	flags.Var(&options.keepStorage, "keep-storage", "Amount of disk space to keep for cache")
 
 	return cmd