bake: add completion to list targets

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

util/cobrautil/completion/completion.go

@@ -1,6 +1,9 @@
 package completion
 
 import (
+	"strings"
+
+	"github.com/docker/buildx/bake"
 	"github.com/spf13/cobra"
 )
 
@@ -10,3 +13,26 @@ type ValidArgsFn func(cmd *cobra.Command, args []string, toComplete string) ([]s
 func Disable(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
 	return nil, cobra.ShellCompDirectiveNoSpace
 }
+
+func BakeTargets(files []string) ValidArgsFn {
+	return func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+		f, err := bake.ReadLocalFiles(files)
+		if err != nil {
+			return nil, cobra.ShellCompDirectiveError
+		}
+		tgts, err := bake.ListTargets(f)
+		if err != nil {
+			return nil, cobra.ShellCompDirectiveError
+		}
+		var filtered []string
+		if toComplete == "" {
+			return tgts, cobra.ShellCompDirectiveNoFileComp
+		}
+		for _, tgt := range tgts {
+			if strings.HasPrefix(tgt, toComplete) {
+				filtered = append(filtered, tgt)
+			}
+		}
+		return filtered, cobra.ShellCompDirectiveNoFileComp
+	}
+}