Merge branch 'master' into search-parent-dirs

* master:
  Fixed markdown errors in README - code samples now correctly formatted.
  Fix use of config.sh in example
  log.py, minimal/do: don't use ansi colour codes if $TERM is blank or 'dumb'
  Use named constants for terminal control codes.
  redo-sh: keep testing even after finding a 'good' shell.
  redo-sh.do: hide warning output from 'which' in some shells.
  redo-sh.do: wrap long lines.
  Handle .do files that start with "#!/" to specify an explicit interpreter.
  minimal/do: don't print an error on exit if we don't build anything.
  bash completions: also mark 'do' as a completable command.
  bash completions: work correctly when $cur is an empty string.
  bash completions: call redo-targets for a more complete list.
  bash completions: work correctly with subdirs, ie. 'redo t/<tab>'
  Sample bash completion rules for redo targets.
  minimal/do: faster deletion of stamp files.
  minimal/do: delete .tmp files if a build fails.
  minimal/do: use ".did" stamp files instead of empty target files.
  minimal/do: use posix shell features instead of dirname/basename.
  Automatically select a good shell instead of relying on /bin/sh.

Conflicts:
	t/clean.do

builder.py

@@ -144,6 +144,9 @@ class BuildJob:
         if vars.VERBOSE: argv[1] += 'v'
         if vars.XTRACE: argv[1] += 'x'
         if vars.VERBOSE or vars.XTRACE: log_('\n')
+        firstline = open(os.path.join(dodir, dofile)).readline().strip()
+        if firstline.startswith('#!/'):
+            argv[0:2] = firstline[2:].split(' ')
         log('%s\n' % _nice(t))
         self.dodir = dodir
         self.basename = basename
@@ -216,7 +219,8 @@ class BuildJob:
         after_t = _try_stat(t)
         st1 = os.fstat(f.fileno())
         st2 = _try_stat(self.tmpname2)
-        if after_t != before_t and not stat.S_ISDIR(after_t.st_mode):
+        if (after_t and after_t != before_t and 
+            not stat.S_ISDIR(after_t.st_mode)):
             err('%s modified %s directly!\n' % (self.argv[2], t))
             err('...you should update $3 (a temp file) or stdout, not $1.\n')
             rv = 206