Revert "internal/flags: fix loading env vars for custom flags (ethere…

…um#28117)"

This reverts commit cd0e8a5.

internal/flags/flags.go

@@ -20,13 +20,11 @@ import (
 	"encoding"
 	"errors"
 	"flag"
-	"fmt"
 	"math/big"
 	"os"
 	"os/user"
 	"path/filepath"
 	"strings"
-	"syscall"
 
 	"github.com/ethereum/go-ethereum/common/math"
 	"github.com/urfave/cli/v2"
@@ -82,14 +80,6 @@ func (f *DirectoryFlag) String() string  { return cli.FlagStringer(f) }
 // Apply called by cli library, grabs variable from environment (if in env)
 // and adds variable to flag set for parsing.
 func (f *DirectoryFlag) Apply(set *flag.FlagSet) error {
-	for _, envVar := range f.EnvVars {
-		envVar = strings.TrimSpace(envVar)
-		if value, found := syscall.Getenv(envVar); found {
-			f.Value.Set(value)
-			f.HasBeenSet = true
-			break
-		}
-	}
 	eachName(f, func(name string) {
 		set.Var(&f.Value, f.Name, f.Usage)
 	})
@@ -177,16 +167,6 @@ func (f *TextMarshalerFlag) IsSet() bool     { return f.HasBeenSet }
 func (f *TextMarshalerFlag) String() string  { return cli.FlagStringer(f) }
 
 func (f *TextMarshalerFlag) Apply(set *flag.FlagSet) error {
-	for _, envVar := range f.EnvVars {
-		envVar = strings.TrimSpace(envVar)
-		if value, found := syscall.Getenv(envVar); found {
-			if err := f.Value.UnmarshalText([]byte(value)); err != nil {
-				return fmt.Errorf("could not parse %q from environment variable %q for flag %s: %s", value, envVar, f.Name, err)
-			}
-			f.HasBeenSet = true
-			break
-		}
-	}
 	eachName(f, func(name string) {
 		set.Var(textMarshalerVal{f.Value}, f.Name, f.Usage)
 	})
@@ -269,16 +249,6 @@ func (f *BigFlag) IsSet() bool     { return f.HasBeenSet }
 func (f *BigFlag) String() string  { return cli.FlagStringer(f) }
 
 func (f *BigFlag) Apply(set *flag.FlagSet) error {
-	for _, envVar := range f.EnvVars {
-		envVar = strings.TrimSpace(envVar)
-		if value, found := syscall.Getenv(envVar); found {
-			if _, ok := f.Value.SetString(value, 10); !ok {
-				return fmt.Errorf("could not parse %q from environment variable %q for flag %s", value, envVar, f.Name)
-			}
-			f.HasBeenSet = true
-			break
-		}
-	}
 	eachName(f, func(name string) {
 		f.Value = new(big.Int)
 		set.Var((*bigValue)(f.Value), f.Name, f.Usage)