Only mkdirp() the .redo directory in one place right at the beginning.

This doesn't really seem to change anything, but it's more correct and
should reveal weirdness (especially an incorrect .redo directory in a
sub-redo) sooner.

redo.py

@@ -22,7 +22,9 @@ if opt.verbose:
 if opt.shuffle:
     os.environ['REDO_SHUFFLE'] = '1'
 
+is_root = False
 if not os.environ.get('REDO_BASE', ''):
+    is_root = True
     base = os.path.commonprefix([os.path.abspath(os.path.dirname(t))
                                  for t in targets] + [os.getcwd()])
     bsplit = base.split('/')
@@ -35,18 +37,21 @@ if not os.environ.get('REDO_BASE', ''):
     os.environ['REDO_STARTDIR'] = os.getcwd()
     os.environ['REDO'] = os.path.abspath(sys.argv[0])
 
+
+import vars, state
+from helpers import *
+
+
+if is_root:
     # FIXME: just wiping out all the locks is kind of cheating.  But we
     # only do this from the toplevel redo process, so unless the user
     # deliberately starts more than one redo on the same repository, it's
     # sort of ok.
+    mkdirp('%s/.redo' % base)
     for f in glob.glob('%s/.redo/lock^*' % base):
         os.unlink(f)
 
 
-import vars, state
-from helpers import *
-
-
 class BuildError(Exception):
     pass
 class BuildLocked(Exception):
@@ -139,7 +144,6 @@ def _build(t):
 
 
 def build(t):
-    mkdirp('%s/.redo' % vars.BASE)
     lock = state.Lock(t)
     lock.lock()
     if not lock.owned: