Since git-rev-parse already checks for the $GIT_DIR environment
variable and that it returns an actual git repository, there is no
need to repeat the checks again here.
This also fixes a problem where git-svn did not work in cases where
.git was a file with a gitdir: link.
[ew: squashed test case,
delay setting GIT_DIR until after `git rev-parse --cdup` to fix t9101,
(thanks to Junio)]
Signed-off-by: Barry Wardell <barry.wardell@gmail.com> Signed-off-by: Eric Wong <normalperson@yhbt.net>