Extract .redo dir state management stuff into its own file.

In preparation for changing the on-disk format eventually, as well as making
the main code more readable.

helpers.py

@@ -81,17 +81,3 @@ def relpath(t, base):
     return '/'.join(tparts)
 
 
-def sname(typ, t, fromdir=None):
-    # FIXME: t.replace(...) is non-reversible and non-unique here!
-    if fromdir:
-        t = os.path.join(fromdir, t)
-    tnew = relpath(t, vars.BASE)
-    v = vars.BASE + ('/.redo/%s^%s' % (typ, tnew.replace('/', '^')))
-    debug2('sname: (%r) %r -> %r\n' % (os.getcwd(), t, tnew))
-    return v
-
-
-def add_dep(t, mode, dep):
-    debug2('add-dep(%r)\n' % t)
-    open(sname('dep', t), 'a').write('%s %s\n'
-                                     % (mode, relpath(dep, vars.BASE)))