posix: Deprecate custom removeAll/mkdirAll implementations. (#4808)

Since go1.8 os.RemoveAll and os.MkdirAll both support long
path names i.e UNC path on windows. The code we are carrying
was directly borrowed from `pkg/os` package and doesn't need
to be in our repo anymore. As a side affect this also
addresses our codecoverage issue.

Refer #4658

cmd/posix-utils_windows.go

@@ -19,11 +19,8 @@
 package cmd
 
 import (
-	"io"
 	"os"
-	"path/filepath"
 	"strings"
-	"syscall"
 
 	os2 "github.com/minio/minio/pkg/x/os"
 )
@@ -42,131 +39,3 @@ func isValidVolname(volname string) bool {
 	// Volname shouldn't have reserved characters on windows in it.
 	return !strings.ContainsAny(volname, `\:*?\"<>|`)
 }
-
-// mkdirAll creates a directory named path,
-// along with any necessary parents, and returns nil,
-// or else returns an error. The permission bits perm are used
-// for all directories that mkdirAll creates. If path is already
-// a directory, mkdirAll does nothing and returns nil.
-func mkdirAll(path string, perm os.FileMode) error {
-	path = preparePath(path)
-	// Fast path: if we can tell whether path is a directory or file, stop with success or error.
-	dir, err := osStat(path)
-	if err == nil {
-		if dir.IsDir() {
-			return nil
-		}
-		return &os.PathError{
-			Op:   "mkdir",
-			Path: path,
-			Err:  syscall.ENOTDIR,
-		}
-	}
-
-	// Slow path: make sure parent exists and then call Mkdir for path.
-	i := len(path)
-	for i > 0 && os.IsPathSeparator(path[i-1]) { // Skip trailing path separator.
-		i--
-	}
-
-	j := i
-	for j > 0 && !os.IsPathSeparator(path[j-1]) { // Scan backward over element.
-		j--
-	}
-
-	if j > 1 {
-		// Create parent
-		parent := path[0 : j-1]
-		if parent != filepath.VolumeName(parent) {
-			err = mkdirAll(parent, perm)
-			if err != nil {
-				return err
-			}
-		}
-	}
-
-	// Parent now exists; invoke Mkdir and use its result.
-	err = os.Mkdir(path, perm)
-	if err != nil {
-		// Handle arguments like "foo/." by
-		// double-checking that directory doesn't exist.
-		dir, err1 := os.Lstat(path)
-		if err1 == nil && dir.IsDir() {
-			return nil
-		}
-		return err
-	}
-	return nil
-}
-
-// removeAll removes path and any children it contains.
-// It removes everything it can but returns the first error
-// it encounters.  If the path does not exist, RemoveAll
-// returns nil (no error).
-func removeAll(path string) error {
-	path = preparePath(path)
-	// Simple case: if Remove works, we're done.
-	err := os.Remove(path)
-	if err == nil || os.IsNotExist(err) {
-		return nil
-	}
-
-	// Otherwise, is this a directory we need to recurse into?
-	dir, serr := os.Lstat(path)
-	if serr != nil {
-		if serr, ok := serr.(*os.PathError); ok && (os.IsNotExist(serr.Err) || serr.Err == syscall.ENOTDIR) {
-			return nil
-		}
-		return serr
-	}
-	if !dir.IsDir() {
-		// Not a directory; return the error from Remove.
-		return err
-	}
-
-	// Directory.
-	fd, err := os.Open(path)
-	if err != nil {
-		if os.IsNotExist(err) {
-			// Race. It was deleted between the Lstat and Open.
-			// Return nil per RemoveAll's docs.
-			return nil
-		}
-		return err
-	}
-
-	// Remove contents & return first error.
-	err = nil
-	for {
-		names, err1 := fd.Readdirnames(4096) // Get 4k entries.
-		for _, name := range names {
-			err1 = removeAll(path + string(os.PathSeparator) + name)
-			if err == nil {
-				err = err1
-			}
-		}
-		if err1 == io.EOF {
-			break
-		}
-		// If Readdirnames returned an error, use it.
-		if err == nil {
-			err = err1
-		}
-		if len(names) == 0 {
-			break
-		}
-	}
-
-	// Close directory, because windows won't remove opened directory.
-	fd.Close()
-
-	// Remove directory.
-	err1 := os.Remove(path)
-	if err1 == nil || os.IsNotExist(err1) {
-		return nil
-	}
-	if err == nil {
-		err = err1
-	}
-	return err
-}