osfs: add Default to avoid repetitive code

Author: mcuadros

osfs/os.go

@@ -18,12 +18,15 @@ const (
 	defaultCreateMode    = 0666
 )
 
+// Default Filesystem representing the root of the os filesystem.
+var Default = &OS{}
+
 // OS is a filesystem based on the os filesystem.
 type OS struct{}
 
 // New returns a new OS filesystem.
 func New(baseDir string) billy.Filesystem {
-	return chroot.New(&OS{}, baseDir)
+	return chroot.New(Default, baseDir)
 }
 
 func (fs *OS) Create(filename string) (billy.File, error) {

osfs/os_js.go

@@ -11,7 +11,11 @@ import (
 // globalMemFs is the global memory fs
 var globalMemFs = memfs.New()
 
+// Default Filesystem representing the root of in-memory filesystem for a
+// js/wasm environment.
+var Default = memfs.New()
+
 // New returns a new OS filesystem.
 func New(baseDir string) billy.Filesystem {
-	return chroot.New(globalMemFs, globalMemFs.Join("/", baseDir))
+	return chroot.New(Default, Default.Join("/", baseDir))
 }