commit 54ae17092986b21431762838f3f8de3a710cc4d2
Author: AJ ONeal <coolaj86@gmail.com>
Date:   Fri Oct 23 13:53:09 2020 -0600

    initial commit with native filesystem

diff --git a/copy.go b/copy.go
new file mode 100644
index 0000000..4a51843
--- /dev/null
+++ b/copy.go
@@ -0,0 +1,190 @@
+package vfscopy
+
+import (
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+)
+
+const (
+	// tmpPermissionForDirectory makes the destination directory writable,
+	// so that stuff can be copied recursively even if any original directory is NOT writable.
+	// See https://github.com/otiai10/copy/pull/9 for more information.
+	tmpPermissionForDirectory = os.FileMode(0755)
+)
+
+// Copy copies src to dest, doesn't matter if src is a directory or a file.
+func Copy(src, dest string, opt ...Options) error {
+	info, err := os.Lstat(src)
+	if err != nil {
+		return err
+	}
+	return switchboard(src, dest, info, assure(opt...))
+}
+
+// switchboard switches proper copy functions regarding file type, etc...
+// If there would be anything else here, add a case to this switchboard.
+func switchboard(src, dest string, info os.FileInfo, opt Options) error {
+	switch {
+	case info.Mode()&os.ModeSymlink != 0:
+		return onsymlink(src, dest, opt)
+	case info.IsDir():
+		return dcopy(src, dest, info, opt)
+	default:
+		return fcopy(src, dest, info, opt)
+	}
+}
+
+// copy decide if this src should be copied or not.
+// Because this "copy" could be called recursively,
+// "info" MUST be given here, NOT nil.
+func copy(src, dest string, info os.FileInfo, opt Options) error {
+	skip, err := opt.Skip(src)
+	if err != nil {
+		return err
+	}
+	if skip {
+		return nil
+	}
+	return switchboard(src, dest, info, opt)
+}
+
+// fcopy is for just a file,
+// with considering existence of parent directory
+// and file permission.
+func fcopy(src, dest string, info os.FileInfo, opt Options) (err error) {
+
+	if err = os.MkdirAll(filepath.Dir(dest), os.ModePerm); err != nil {
+		return
+	}
+
+	f, err := os.Create(dest)
+	if err != nil {
+		return
+	}
+	defer fclose(f, &err)
+
+	if err = os.Chmod(f.Name(), info.Mode()|opt.AddPermission); err != nil {
+		return
+	}
+
+	s, err := os.Open(src)
+	if err != nil {
+		return
+	}
+	defer fclose(s, &err)
+
+	if _, err = io.Copy(f, s); err != nil {
+		return
+	}
+
+	if opt.Sync {
+		err = f.Sync()
+	}
+
+	return
+}
+
+// dcopy is for a directory,
+// with scanning contents inside the directory
+// and pass everything to "copy" recursively.
+func dcopy(srcdir, destdir string, info os.FileInfo, opt Options) (err error) {
+
+	originalMode := info.Mode()
+
+	// Make dest dir with 0755 so that everything writable.
+	if err = os.MkdirAll(destdir, tmpPermissionForDirectory); err != nil {
+		return
+	}
+	// Recover dir mode with original one.
+	defer chmod(destdir, originalMode|opt.AddPermission, &err)
+
+	contents, err := ioutil.ReadDir(srcdir)
+	if err != nil {
+		return
+	}
+
+	for _, content := range contents {
+		cs, cd := filepath.Join(srcdir, content.Name()), filepath.Join(destdir, content.Name())
+
+		if err = copy(cs, cd, content, opt); err != nil {
+			// If any error, exit immediately
+			return
+		}
+	}
+
+	return
+}
+
+func onsymlink(src, dest string, opt Options) error {
+
+	switch opt.OnSymlink(src) {
+	case Shallow:
+		return lcopy(src, dest)
+	case Deep:
+		orig, err := filepath.EvalSymlinks(src)
+		if err != nil {
+			return err
+		}
+		info, err := os.Lstat(orig)
+		if err != nil {
+			return err
+		}
+		return copy(orig, dest, info, opt)
+	case Skip:
+		fallthrough
+	default:
+		return nil // do nothing
+	}
+}
+
+// lcopy is for a symlink,
+// with just creating a new symlink by replicating src symlink.
+func lcopy(src, dest string) error {
+	src, err := os.Readlink(src)
+	if err != nil {
+		return err
+	}
+
+	// Create the directories on the path to the dest symlink.
+	if err = os.MkdirAll(filepath.Dir(dest), os.ModePerm); err != nil {
+		return err
+	}
+
+	return os.Symlink(src, dest)
+}
+
+// fclose ANYHOW closes file,
+// with asiging error raised during Close,
+// BUT respecting the error already reported.
+func fclose(f *os.File, reported *error) {
+	if err := f.Close(); *reported == nil {
+		*reported = err
+	}
+}
+
+// chmod ANYHOW changes file mode,
+// with asiging error raised during Chmod,
+// BUT respecting the error already reported.
+func chmod(dir string, mode os.FileMode, reported *error) {
+	if err := os.Chmod(dir, mode); *reported == nil {
+		*reported = err
+	}
+}
+
+// assure Options struct, should be called only once.
+// All optional values MUST NOT BE nil/zero after assured.
+func assure(opts ...Options) Options {
+	if len(opts) == 0 {
+		return getDefaultOptions()
+	}
+	defopt := getDefaultOptions()
+	if opts[0].OnSymlink == nil {
+		opts[0].OnSymlink = defopt.OnSymlink
+	}
+	if opts[0].Skip == nil {
+		opts[0].Skip = defopt.Skip
+	}
+	return opts[0]
+}
diff --git a/copy_test.go b/copy_test.go
new file mode 100644
index 0000000..47fca9f
--- /dev/null
+++ b/copy_test.go
@@ -0,0 +1,18 @@
+package vfscopy
+
+import (
+	"testing"
+)
+
+func TestRecursiveCopy(t *testing.T) {
+	{
+		opts := Options{
+			OnSymlink: func (path string) SymlinkAction {
+				return Shallow
+			},
+		}
+		if err := Copy( "./fixtures/src/", "/tmp/dst/", opts,); nil != err {
+			t.Fatalf("error: %v", err)
+		}
+	}
+}
diff --git a/fixtures/src/file-a.txt b/fixtures/src/file-a.txt
new file mode 100644
index 0000000..e965047
--- /dev/null
+++ b/fixtures/src/file-a.txt
@@ -0,0 +1 @@
+Hello
diff --git a/fixtures/src/foo-sym.txt b/fixtures/src/foo-sym.txt
new file mode 120000
index 0000000..996f178
--- /dev/null
+++ b/fixtures/src/foo-sym.txt
@@ -0,0 +1 @@
+foo.txt
\ No newline at end of file
diff --git a/fixtures/src/foo.txt b/fixtures/src/foo.txt
new file mode 100644
index 0000000..bc56c4d
--- /dev/null
+++ b/fixtures/src/foo.txt
@@ -0,0 +1 @@
+Foo
diff --git a/fixtures/src/hello.txt b/fixtures/src/hello.txt
new file mode 100644
index 0000000..e965047
--- /dev/null
+++ b/fixtures/src/hello.txt
@@ -0,0 +1 @@
+Hello
diff --git a/fixtures/src/world.txt b/fixtures/src/world.txt
new file mode 100644
index 0000000..216e97c
--- /dev/null
+++ b/fixtures/src/world.txt
@@ -0,0 +1 @@
+World
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..880e9a2
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,3 @@
+module git.rootprojects.org/root/vfscopy
+
+go 1.15
diff --git a/options.go b/options.go
new file mode 100644
index 0000000..c529339
--- /dev/null
+++ b/options.go
@@ -0,0 +1,46 @@
+package vfscopy
+
+import "os"
+
+// Options specifies optional actions on copying.
+type Options struct {
+	// OnSymlink can specify what to do on symlink
+	OnSymlink func(src string) SymlinkAction
+	// Skip can specify which files should be skipped
+	Skip func(src string) (bool, error)
+	// AddPermission to every entities,
+	// NO MORE THAN 0777
+	AddPermission os.FileMode
+	// Sync file after copy.
+	// Useful in case when file must be on the disk
+	// (in case crash happens, for example),
+	// at the expense of some performance penalty
+	Sync bool
+}
+
+// SymlinkAction represents what to do on symlink.
+type SymlinkAction int
+
+const (
+	// Deep creates hard-copy of contents.
+	Deep SymlinkAction = iota
+	// Shallow creates new symlink to the dest of symlink.
+	Shallow
+	// Skip does nothing with symlink.
+	Skip
+)
+
+// getDefaultOptions provides default options,
+// which would be modified by usage-side.
+func getDefaultOptions() Options {
+	return Options{
+		OnSymlink: func(string) SymlinkAction {
+			return Shallow // Do shallow copy
+		},
+		Skip: func(string) (bool, error) {
+			return false, nil // Don't skip
+		},
+		AddPermission: 0,     // Add nothing
+		Sync:          false, // Do not sync
+	}
+}