Revert "Make the exec command default to a login shell. Fixes #546"

This reverts commit 8ad90a6.
This reverts commit 38262fd.

cli/exec.go

@@ -7,7 +7,6 @@ import (
 	"os"
 	osexec "os/exec"
 	"os/signal"
-	"path/filepath"
 	"runtime"
 	"strings"
 	"syscall"
@@ -85,6 +84,7 @@ func ConfigureExecCommand(app *kingpin.Application) {
 		StringVar(&input.ProfileName)
 
 	cmd.Arg("cmd", "Command to execute, defaults to $SHELL").
+		Default(os.Getenv("SHELL")).
 		StringVar(&input.Command)
 
 	cmd.Arg("args", "Command arguments").
@@ -95,36 +95,11 @@ func ConfigureExecCommand(app *kingpin.Application) {
 		input.Config.MfaPromptMethod = GlobalFlags.PromptDriver
 		input.Config.NonChainedGetSessionTokenDuration = input.SessionDuration
 		input.Config.AssumeRoleDuration = input.SessionDuration
-		if input.Command == "" {
-			input.Command, input.Args = getDefaultShellCmd()
-		}
-		if input.Command == "" {
-			app.Fatalf("Argument 'cmd' not provided, and SHELL not present, try --help")
-		}
 		app.FatalIfError(ExecCommand(input), "")
 		return nil
 	})
 }
 
-func getDefaultShellCmd() (string, []string) {
-	shellCmd := os.Getenv("SHELL")
-	s := strings.ToLower(shellCmd)
-	s = strings.TrimSuffix(s, ".exe")
-	s = filepath.Base(s)
-
-	// for shells that support it start an interactive login shell
-	shellArgs := []string{}
-	if s == "sh" ||
-		s == "bash" ||
-		s == "zsh" ||
-		s == "csh" ||
-		s == "fish" {
-		shellArgs = []string{"-l"}
-	}
-
-	return shellCmd, shellArgs
-}
-
 func ExecCommand(input ExecCommandInput) error {
 	if os.Getenv("AWS_VAULT") != "" {
 		return fmt.Errorf("aws-vault sessions should be nested with care, unset $AWS_VAULT to force")