Revert "Use v2 of urfave/cli"

This reverts commit 17df897c32.

That did not work *at all*... We really need some tests for all of
this.

utils/flags.go

@@ -8,7 +8,7 @@ import (
 	"strings"
 
 	"github.com/fatih/structs"
-	"github.com/urfave/cli/v2"
+	"github.com/urfave/cli"
 	"github.com/yudai/hcl"
 
 	"github.com/sorenisanerd/gotty/pkg/homedir"
@@ -36,24 +36,24 @@ func GenerateFlags(options ...interface{}) (flags []cli.Flag, mappings map[strin
 
 			switch field.Kind() {
 			case reflect.String:
-				flags = append(flags, &cli.StringFlag{
-					Name:    flagName,
-					Value:   field.Value().(string),
-					Usage:   flagDescription,
-					EnvVars: []string{envName},
+				flags = append(flags, cli.StringFlag{
+					Name:   flagName,
+					Value:  field.Value().(string),
+					Usage:  flagDescription,
+					EnvVar: envName,
 				})
 			case reflect.Bool:
-				flags = append(flags, &cli.BoolFlag{
-					Name:    flagName,
-					Usage:   flagDescription,
-					EnvVars: []string{envName},
+				flags = append(flags, cli.BoolFlag{
+					Name:   flagName,
+					Usage:  flagDescription,
+					EnvVar: envName,
 				})
 			case reflect.Int:
-				flags = append(flags, &cli.IntFlag{
-					Name:    flagName,
-					Value:   field.Value().(int),
-					Usage:   flagDescription,
-					EnvVars: []string{envName},
+				flags = append(flags, cli.IntFlag{
+					Name:   flagName,
+					Value:  field.Value().(int),
+					Usage:  flagDescription,
+					EnvVar: envName,
 				})
 			}
 		}