vfs: factor flags into vfsflags and remove global variables

vfs/vfsflags/vfsflags_unix.go

@@ -0,0 +1,19 @@
+// +build linux darwin freebsd
+
+package vfsflags
+
+import (
+	"github.com/spf13/pflag"
+	"golang.org/x/sys/unix"
+)
+
+// add any extra platform specific flags
+func platformFlags(flags *pflag.FlagSet) {
+	flags.IntVarP(&Opt.Umask, "umask", "", Opt.Umask, "Override the permission bits set by the filesystem.")
+	Opt.Umask = unix.Umask(0) // read the umask
+	unix.Umask(Opt.Umask)     // set it back to what it was
+	Opt.UID = uint32(unix.Geteuid())
+	Opt.GID = uint32(unix.Getegid())
+	flags.Uint32VarP(&Opt.UID, "uid", "", Opt.UID, "Override the uid field set by the filesystem.")
+	flags.Uint32VarP(&Opt.GID, "gid", "", Opt.GID, "Override the gid field set by the filesystem.")
+}