Export ToFileMode and FromFileMode.

For the sake of sanity, we really should be offering _some_ way for
users of memfile to get the file mode right.  These two are what we use
internally, so they make perfect sense to expose.

attrs.go

@@ -32,7 +32,7 @@ func (fi *fileInfo) Name() string { return fi.name }
 func (fi *fileInfo) Size() int64 { return int64(fi.stat.Size) }
 
 // Mode returns file mode bits.
-func (fi *fileInfo) Mode() os.FileMode { return toFileMode(fi.stat.Mode) }
+func (fi *fileInfo) Mode() os.FileMode { return ToFileMode(fi.stat.Mode) }
 
 // ModTime returns the last modification time of the file.
 func (fi *fileInfo) ModTime() time.Time { return time.Unix(int64(fi.stat.Mtime), 0) }
@@ -92,7 +92,7 @@ func fileStatFromInfo(fi os.FileInfo) (uint32, *FileStat) {
 
 	fileStat := &FileStat{
 		Size:  uint64(fi.Size()),
-		Mode:  fromFileMode(fi.Mode()),
+		Mode:  FromFileMode(fi.Mode()),
 		Mtime: uint32(mtime),
 		Atime: uint32(atime),
 	}

client.go

@@ -2009,7 +2009,7 @@ func flags(f int) uint32 {
 
 // toChmodPerm converts Go permission bits to POSIX permission bits.
 //
-// This differs from fromFileMode in that we preserve the POSIX versions of
+// This differs from FromFileMode in that we preserve the POSIX versions of
 // setuid, setgid and sticky in m, because we've historically supported those
 // bits, and we mask off any non-permission bits.
 func toChmodPerm(m os.FileMode) (perm uint32) {

ls_formatting.go

@@ -47,7 +47,7 @@ func runLs(idLookup NameLookupFileLister, dirent os.FileInfo) string {
 	// format:
 	// {directory / char device / etc}{rwxrwxrwx}  {number of links} owner group size month day [time (this year) | year (otherwise)] name
 
-	symPerms := sshfx.FileMode(fromFileMode(dirent.Mode())).String()
+	symPerms := sshfx.FileMode(FromFileMode(dirent.Mode())).String()
 
 	var numLinks uint64 = 1
 	uid, gid := "0", "0"

stat_posix.go

@@ -49,8 +49,8 @@ func isRegular(mode uint32) bool {
 	return mode&S_IFMT == syscall.S_IFREG
 }
 
-// toFileMode converts sftp filemode bits to the os.FileMode specification
-func toFileMode(mode uint32) os.FileMode {
+// ToFileMode converts sftp filemode bits to the os.FileMode specification
+func ToFileMode(mode uint32) os.FileMode {
 	var fm = os.FileMode(mode & 0777)
 
 	switch mode & S_IFMT {
@@ -83,8 +83,8 @@ func toFileMode(mode uint32) os.FileMode {
 	return fm
 }
 
-// fromFileMode converts from the os.FileMode specification to sftp filemode bits
-func fromFileMode(mode os.FileMode) uint32 {
+// FromFileMode converts from the os.FileMode specification to sftp filemode bits
+func FromFileMode(mode os.FileMode) uint32 {
 	ret := uint32(mode & os.ModePerm)
 
 	switch mode & os.ModeType {