cli/command/image: remove use of docker/docker/pkg/urlutil

pkg/urlutil (despite its poorly chosen name) is not really intended as a
generic utility to handle URLs, and should only be used by the builder to
handle (remote) build contexts.

The `IsURL()` function only does a very rudimentary check for `http(s)://`
prefixes, without any other validation, but due to its name may give
incorrect expectations.

As we're deprecating this package for uses other than for build-contexts,
this patch replaces this instance of the utility for a local function.

While changing, also cleaned up some intermediate variables, and made
the logic slightly more descriptive.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cli/command/image/import.go

@@ -2,15 +2,14 @@ package image
 
 import (
 	"context"
-	"io"
 	"os"
+	"strings"
 
 	"github.com/docker/cli/cli"
 	"github.com/docker/cli/cli/command"
 	dockeropts "github.com/docker/cli/opts"
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/pkg/jsonmessage"
-	"github.com/docker/docker/pkg/urlutil"
 	"github.com/spf13/cobra"
 )
 
@@ -50,37 +49,37 @@ func NewImportCommand(dockerCli command.Cli) *cobra.Command {
 }
 
 func runImport(dockerCli command.Cli, options importOptions) error {
-	var (
-		in      io.Reader
-		srcName = options.source
-	)
-
-	if options.source == "-" {
-		in = dockerCli.In()
-	} else if !urlutil.IsURL(options.source) {
-		srcName = "-"
+	var source types.ImageImportSource
+	switch {
+	case options.source == "-":
+		// import from STDIN
+		source = types.ImageImportSource{
+			Source:     dockerCli.In(),
+			SourceName: options.source,
+		}
+	case strings.HasPrefix(options.source, "https://"), strings.HasPrefix(options.source, "http://"):
+		// import from a remote source (handled by the daemon)
+		source = types.ImageImportSource{
+			SourceName: options.source,
+		}
+	default:
+		// import from a local file
 		file, err := os.Open(options.source)
 		if err != nil {
 			return err
 		}
 		defer file.Close()
-		in = file
+		source = types.ImageImportSource{
+			Source:     file,
+			SourceName: "-",
+		}
 	}
 
-	source := types.ImageImportSource{
-		Source:     in,
-		SourceName: srcName,
-	}
-
-	importOptions := types.ImageImportOptions{
+	responseBody, err := dockerCli.Client().ImageImport(context.Background(), source, options.reference, types.ImageImportOptions{
 		Message:  options.message,
 		Changes:  options.changes.GetAll(),
 		Platform: options.platform,
-	}
-
-	clnt := dockerCli.Client()
-
-	responseBody, err := clnt.ImageImport(context.Background(), source, options.reference, importOptions)
+	})
 	if err != nil {
 		return err
 	}