git wrapper: basic fixes.

git wrapper: basic fixes.

Updates to fix the nits found during the list discussion.

 - Lose PATH_TO_MAN; just rely on execlp() to find whereever the
   "man" command is installed.

 - Do not randomly chdir(), but concatenate to the current
   working directory only if the given path is not absolute.

 - Lose use of glob(); read from exec_path and do sorting
   ourselves -- it is not that much more work.

Signed-off-by: Junio C Hamano <junkio@cox.net>