redo-whichdo: a command that explains the .do search path for a target.

For example:

$ redo-whichdo a/b/c/.x.y

- a/b/c.x.y.do
- a/b/default.x.y.do
- a/b/default.y.do
- a/b/default.do
- a/default.x.y.do
- a/default.y.do
- a/default.do
- default.x.y.do
- default.y.do
+ default.do
1 a/b/c.x.y
2 a/b/c.x.y

Lines starting with '-' mean a potential .do file that did not exist,
so we moved onto the next choice (but consider using redo-ifcreate in
case it gets created).  '+' means the .do file we actually chose.  '1'
and '2' are the $1 and $2 to pass along to the given .do file if you want to
call it for the given target.

(The output format is a little weird to make sure it's parseable with
sh 'read x y' calls, even when filenames contain spaces or special
characters.)

redo-whichdo.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python
+import sys, os
+
+import vars_init
+vars_init.init([])
+
+import builder
+from log import err
+
+if len(sys.argv[1:]) != 1:
+    err('%s: exactly one argument expected.\n' % sys.argv[0])
+    sys.exit(1)
+
+want = sys.argv[1]
+for dodir,dofile,basedir,basename,ext in builder.possible_do_files(os.path.abspath(want)):
+    dopath = os.path.join('/', dodir, dofile)
+    relpath = os.path.relpath(dopath, '.')
+    exists = os.path.exists(dopath)
+    assert('\n' not in relpath)
+    if exists:
+      print '+', relpath
+      assert('\n' not in basename)
+      assert('\n' not in ext)
+      print '1', basename+ext
+      print '2', basename
+      sys.exit(0)
+    else:
+      print '-', relpath
+sys.exit(1)   # no appropriate dofile found