chore: fix sort invalid tag test, minor cleanup

cmd/git-chglog/main.go

@@ -126,12 +126,6 @@ func CreateApp(actionFunc cli.ActionFunc) *cli.App {
 			Usage: "Regular expression of tag filter. Is specified, only matched tags will be picked",
 		},
 
-		// sort-by-date
-		cli.BoolFlag{
-			Name:  "sort-by-date",
-			Usage: "Sort tags by date of creation. Use with caution as there are known issues when generating a changelog that contains multiple major versions.",
-		},
-
 		// sort-by-version
 		cli.BoolFlag{
 			Name:  "sort-by-version",

tag_reader_test.go

@@ -135,7 +135,7 @@ func TestTagReader(t *testing.T) {
 	)
 }
 
-func TestTagReaderSortByTag(t *testing.T) {
+func TestTagReaderSortTagsByVersion(t *testing.T) {
 	assert := assert.New(t)
 	client := &mockClient{
 		ReturnExec: func(subcmd string, args ...string) (string, error) {
@@ -236,7 +236,7 @@ func TestTagReaderSortByTag(t *testing.T) {
 	assert.Equal(expected, actual)
 }
 
-func TestTagReaderSortByTagWithInvalidTag(t *testing.T) {
+func TestTagReaderSortTagsByVersionWithInvalidTag(t *testing.T) {
 	assert := assert.New(t)
 	client := &mockClient{
 		ReturnExec: func(subcmd string, args ...string) (string, error) {
@@ -255,6 +255,6 @@ func TestTagReaderSortByTagWithInvalidTag(t *testing.T) {
 		},
 	}
 
-	_, err := newTagReader(client, "", false).ReadAll()
+	_, err := newTagReader(client, "", true).ReadAll()
 	assert.Error(err)
 }