test.do would run all its subtasks even though it used 'redo-ifchange'.

The behaviour is what we wanted, but it shouldn't have worked.  So fix the
bug in redo-ifchange, then change test.do to use 'redo' instead so it
continues to do what we want, only for the right reason.

(The bug is that 'redo-ifchange dirname', which runs dirname/all.do, didn't
result in stamps getting checked correctly.)

redo-ifchange.py

@@ -5,6 +5,8 @@ from helpers import debug, err, mkdirp, unlink
 
 
 def dirty_deps(t, depth):
+    if os.path.exists('%s/.' % t):
+        t = '%s/all' % t
     debug('%s?%s\n' % (depth, t))
     if state.isbuilt(t):
         debug('%s-- DIRTY (built)\n' % depth)

test.do

@@ -1,2 +1,2 @@
-redo-ifchange t/c.c t/test
-
+redo-ifchange t/c.c
+redo t/test