Fix new-workdir (again) to work on bare repositories

My day-job workflow involves using multiple workdirs attached to a
bunch of bare repositories.  Such repositories are stored inside of
a directory called "foo.git", which means `git rev-parse --git-dir`
will return "." and not ".git".  Under such conditions new-workdir
was getting confused about where the Git repository it was supplied
is actually located.

If we get "." for the result of --git-dir query it means we should
use the user supplied path as-is, and not attempt to perform any
magic on it, as the path is directly to the repository.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/workdir/git-new-workdir

@@ -24,10 +24,14 @@ git_dir=$(cd "$orig_git" 2>/dev/null &&
   git rev-parse --git-dir 2>/dev/null) ||
   die "\"$orig_git\" is not a git repository!"
 
-if test "$git_dir" = ".git"
-then
+case "$git_dir" in
+.git)
 	git_dir="$orig_git/.git"
-fi
+	;;
+.)
+	git_dir=$orig_git
+	;;
+esac
 
 # don't link to a workdir
 if test -L "$git_dir/config"