git grep in .

Hello,

git grep behaves wrongly if I give it . as path to search in.

E.g.

	uzeisberger@io:~/gsrc/git$ git version
	git version 1.4.0

	uzeisberger@io:~/gsrc/git$ git grep git-grep 
	.gitignore:git-grep
	Documentation/git-grep.txt:git-grep(1)
	Documentation/git-grep.txt:git-grep - Print lines matching a pattern
	Documentation/git-grep.txt:'git-grep' [--cached]
	Documentation/git.txt:gitlink:git-grep[1]::
	Makefile:       git-grep$X git-add$X git-rm$X git-rev-list$X \
	builtin-grep.c:"git-grep <option>* <rev>* [-e] <pattern> [<path>...]";

	uzeisberger@io:~/gsrc/git$ git grep git-grep .

	uzeisberger@io:~/gsrc/git$ 

I'd expect that `git grep git-grep .` gives the same results as `git grep git-grep`.

Best regards Uwe