Remove batcharchive dependency on common.IsDirectory

client/internal/common/utils.go

Index: client/internal/common/utils.go
diff --git a/client/internal/common/utils.go b/client/internal/common/utils.go
index 9bd61b07d593c1b073578443b83b0d0c2a747636..718cd5bfd41a5cfcae9a7dc5a82d39c156e9412f 100644
--- a/client/internal/common/utils.go
+++ b/client/internal/common/utils.go
@@ -12,12 +12,6 @@ import (
 	"github.com/luci/luci-go/common/system/terminal"
 )
 
-// IsDirectory returns true if path is a directory and is accessible.
-func IsDirectory(path string) bool {
-	fileInfo, err := os.Stat(path)
-	return err == nil && fileInfo.IsDir()
-}
-
 // IsWindows returns True when running on the best OS there is.
 func IsWindows() bool {
 	return runtime.GOOS == "windows"