delete tempdir

	'git subtree rejoin' option to do the same as --rejoin, eg. after a
	  rebase

	--prefix doesn't force the subtree correctly in merge/pull:
	"-s subtree" should be given an explicit subtree option?
		There doesn't seem to be a way to do this.  We'd have to
		patch git-merge-subtree.  Ugh.
		(but we could avoid this problem by generating squashes with
		exactly the right subtree structure, rather than using
		subtree merge...)

	add a 'push' subcommand to parallel 'pull'
	
	add a 'log' subcommand to see what's new in a subtree?

	add to-submodule and from-submodule commands

	automated tests for --squash stuff

	test.sh fails in msysgit?
		sort error - see Thell's email

	"add" command non-obviously requires a commitid; would be easier if
		it had a "pull" sort of mode instead

	"pull" and "merge" commands should fail if you've never merged
		that --prefix before
		
	docs should provide an example of "add"
	
	note that the initial split doesn't *have* to have a commitid
		specified... that's just an optimization

	if you try to add (or maybe merge?) with an invalid commitid, you
		get a misleading "prefix must end with /" message from
		one of the other git tools that git-subtree calls.  Should
		detect this situation and print the *real* problem.
	
	In fact, the prefix should *not* end with slash, and we
		should detect (and fix) it if it does.  Otherwise the
		log message looks weird.