fix #99: default output dir to where the input file is

cmd/um/main.go

@@ -8,6 +8,7 @@ import (
 	"io"
 	"os"
 	"os/signal"
+	"path"
 	"path/filepath"
 	"runtime"
 	"runtime/debug"
@@ -84,6 +85,11 @@ func printSupportedExtensions() {
 }
 
 func appMain(c *cli.Context) (err error) {
+	cwd, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+
 	if c.Bool("supported-ext") {
 		printSupportedExtensions()
 		return nil
@@ -92,10 +98,7 @@ func appMain(c *cli.Context) (err error) {
 	if input == "" {
 		switch c.Args().Len() {
 		case 0:
-			input, err = os.Getwd()
-			if err != nil {
-				return err
-			}
+			input = cwd
 		case 1:
 			input = c.Args().Get(0)
 		default:
@@ -104,22 +107,20 @@ func appMain(c *cli.Context) (err error) {
 	}
 
 	output := c.String("output")
-	if output == "" {
-		var err error
-		output, err = os.Getwd()
-		if err != nil {
-			return err
-		}
-		if input == output {
-			return errors.New("input and output path are same")
-		}
-	}
-
 	inputStat, err := os.Stat(input)
 	if err != nil {
 		return err
 	}
 
+	if output == "" {
+		// Default to where the input is
+		if inputStat.IsDir() {
+			output = input
+		} else {
+			output = path.Dir(input)
+		}
+	}
+
 	outputStat, err := os.Stat(output)
 	if err != nil {
 		if errors.Is(err, os.ErrNotExist) {