Add basic interactive overwrite strategy

Available options:

- Do not copy
- Overwrite dest
- Copy source as dest.dist

internal/template/copy.go

@@ -1,9 +1,9 @@
 package template
 
 import (
+	"fmt"
 	"io"
 	"io/ioutil"
-	"log"
 	"os"
 	"path/filepath"
 	"strings"
@@ -13,6 +13,7 @@ import (
 	"gopkg.in/src-d/go-billy.v4"
 
 	"github.com/Masterminds/sprig"
+	"github.com/mattn/go-zglob"
 	"github.com/pkg/errors"
 )
 
@@ -43,12 +44,12 @@ func CopyDir(vfs billy.Filesystem, baseDir string, dst string, opts *Option) err
 		}
 
 		for _, p := range opts.IgnorePatterns {
-			match, err := filepath.Match(p, srcPath)
+			match, err := zglob.Match(p, strings.TrimPrefix(srcPath, "./"))
 			if err != nil {
 				return errors.Wrap(err, "could not match ignored file")
 			}
 			if match {
-				log.Printf("Ignoring %s.", srcPath)
+				fmt.Printf("Ignoring %s.\n", srcPath)
 				return nil
 			}
 		}
@@ -61,7 +62,7 @@ func CopyDir(vfs billy.Filesystem, baseDir string, dst string, opts *Option) err
 		dstPath := filepath.Join(dst, relSrcPath)
 
 		if info.IsDir() {
-			log.Printf("creating dir '%s'", dstPath)
+			fmt.Printf("Creating dir '%s'.\n", dstPath)
 			if err := os.MkdirAll(dstPath, 0755); err != nil {
 				return errors.Wrapf(err, "could not create directory '%s'", dstPath)
 			}
@@ -89,6 +90,44 @@ func CopyFile(vfs billy.Filesystem, src, dst string, opts *Option) (err error) {
 		opts = &Option{}
 	}
 
+	stat, err := os.Stat(dst)
+	if err != nil && !os.IsNotExist(err) {
+		return err
+	}
+
+	// If dst exists
+	if stat != nil {
+		strategy := opts.PreferredStrategy
+
+		if opts.Unnattended && opts.PreferredStrategy == -1 {
+			strategy = defaultStrategy
+		}
+
+		if opts.PreferredStrategy == -1 {
+			var useAsPreferredStrategy bool
+
+			strategy, useAsPreferredStrategy, err = askOverwriteStrategy(dst)
+			if err != nil {
+				return errors.Wrap(err, "could not ask for overwrite strategy")
+			}
+
+			if useAsPreferredStrategy {
+				opts.PreferredStrategy = strategy
+			}
+		}
+
+		switch strategy {
+		case CopyAsDist:
+			fmt.Printf("Using '%s.dist' as destination file.\n", dst)
+			dst += ".dist"
+		case DoNotCopy:
+			fmt.Printf("Skipping existing file '%s'.\n", dst)
+			return nil
+		default:
+			return nil
+		}
+	}
+
 	if !strings.HasSuffix(src, opts.TemplateExt) {
 		return copyFile(vfs, src, dst)
 	}
@@ -111,7 +150,7 @@ func CopyFile(vfs billy.Filesystem, src, dst string, opts *Option) (err error) {
 
 	dst = strings.TrimSuffix(dst, opts.TemplateExt)
 
-	log.Printf("templating file from '%s' to '%s'", src, dst)
+	fmt.Printf("Templating file from '%s' to '%s'.\n", src, dst)
 
 	out, err := os.Create(dst)
 	if err != nil {
@@ -135,7 +174,7 @@ func CopyFile(vfs billy.Filesystem, src, dst string, opts *Option) (err error) {
 }
 
 func copyFile(vfs billy.Filesystem, src, dst string) (err error) {
-	log.Printf("copying file '%s' to '%s'", src, dst)
+	fmt.Printf("Copying file '%s' to '%s'.\n", src, dst)
 
 	in, err := vfs.Open(src)
 	if err != nil {

internal/template/error.go

@@ -0,0 +1,7 @@
+package template
+
+import "github.com/pkg/errors"
+
+var (
+	ErrUnexpectedOverwriteStrategy = errors.New("unexpected overwrite strategy")
+)

internal/template/option.go

@@ -1,7 +1,9 @@
 package template
 
 type Option struct {
-	IgnorePatterns []string
-	TemplateData   Data
-	TemplateExt    string
+	IgnorePatterns    []string
+	TemplateData      Data
+	TemplateExt       string
+	Unnattended       bool
+	PreferredStrategy Strategy
 }

internal/template/strategy.go

@@ -0,0 +1,62 @@
+package template
+
+import (
+	"fmt"
+
+	"github.com/manifoldco/promptui"
+	"github.com/pkg/errors"
+)
+
+type Strategy int
+
+const (
+	Undefined Strategy = -1
+	Overwrite Strategy = iota
+	CopyAsDist
+	DoNotCopy
+)
+
+// nolint: gochecknoglobals
+var defaultStrategy = CopyAsDist
+
+func askOverwriteStrategy(dst string) (Strategy, bool, error) {
+	strategyPrompt := promptui.Select{
+		Label: fmt.Sprintf("The file '%s' already exists. What do you want to do ?", dst),
+		Items: []string{
+			"Leave <dest> file as is",
+			"Copy source file as '<dest>.dist'",
+			"Overwrite '<dest>' with source file",
+		},
+	}
+
+	strategySelectedIndex, _, err := strategyPrompt.Run()
+	if err != nil {
+		return -1, false, errors.Wrap(err, "could not prompt for overwrite strategy")
+	}
+
+	asPreferredStrategyPrompt := promptui.Select{
+		Label: "Do you want to apply this strategy to all files ?",
+		Items: []string{
+			"Yes",
+			"No",
+		},
+	}
+
+	preferredSelectedIndex, _, err := asPreferredStrategyPrompt.Run()
+	if err != nil {
+		return -1, false, errors.Wrap(err, "could not prompt for preferred strategy")
+	}
+
+	useAsPreferredStrategy := preferredSelectedIndex == 0
+
+	switch strategySelectedIndex {
+	case 0:
+		return DoNotCopy, useAsPreferredStrategy, nil
+	case 1:
+		return CopyAsDist, useAsPreferredStrategy, nil
+	case 2:
+		return Overwrite, useAsPreferredStrategy, nil
+	default:
+		return -1, false, ErrUnexpectedOverwriteStrategy
+	}
+}