Adding the PrintGroupNames option (#67)

* Adding the PrintGroupNames option
* Adding groupNumbers parameter go the PrintGroupNames method
---------
Co-authored-by: Andy Gorman <andyg@apacesystems.com>

Author: agorman

exiftool.go

@@ -397,6 +397,16 @@ func CoordFormant(format string) func(*Exiftool) error {
 	}
 }
 
+// PrintGroupNames prints the group names for each tag based on the pass group number(s), (activates Exiftool's '-G' paramater)
+// Sample :
+//	e, err := NewExiftool(PrintGroupNames("0"))
+func PrintGroupNames(groupNumbers string) func(*Exiftool) error {
+	return func(e *Exiftool) error {
+		e.extraInitArgs = append(e.extraInitArgs, "-G"+groupNumbers)
+		return nil
+	}
+}
+
 // BackupOriginal backs up the original file when writing the file metadata
 // instead of overwriting the original (activates Exiftool's '-overwrite_original' parameter)
 // Sample :

exiftool_test.go

@@ -432,6 +432,40 @@ func TestCoordFormat(t *testing.T) {
 	assert.Equal(t, "+43.467448", latitude)
 }
 
+func TestPrintGroupNames(t *testing.T) {
+	t.Parallel()
+
+	eWithout, err := NewExiftool()
+	assert.Nil(t, err)
+	defer eWithout.Close()
+	metas := eWithout.ExtractMetadata("./testdata/20190404_131804.jpg")
+	assert.Equal(t, 1, len(metas))
+	assert.Nil(t, metas[0].Err)
+	width, err := metas[0].GetString("ImageWidth")
+	assert.Nil(t, err)
+	assert.Equal(t, `64`, width)
+
+	eWith, err := NewExiftool(PrintGroupNames("0"))
+	assert.Nil(t, err)
+	defer eWith.Close()
+	metas = eWith.ExtractMetadata("./testdata/20190404_131804.jpg")
+	assert.Equal(t, 1, len(metas))
+	assert.Nil(t, metas[0].Err)
+	width, err = metas[0].GetString("File:ImageWidth")
+	assert.Nil(t, err)
+	assert.Equal(t, "64", width)
+
+	eWith, err = NewExiftool(PrintGroupNames("0:1:2:3:4:5:6:7"))
+	assert.Nil(t, err)
+	defer eWith.Close()
+	metas = eWith.ExtractMetadata("./testdata/20190404_131804.jpg")
+	assert.Equal(t, 1, len(metas))
+	assert.Nil(t, metas[0].Err)
+	width, err = metas[0].GetString("File:Image:Main:JPEG-SOF0:ID-ImageWidth:ImageWidth")
+	assert.Nil(t, err)
+	assert.Equal(t, "64", width)
+}
+
 func TestSetExiftoolBinaryPath(t *testing.T) {
 	t.Parallel()