This makes it be the same as in the linux runshell.
It may be that bundle/ used to have all the necessary binaries in it,
but that seems unlikely. I think that the breakage fixed by my previous
commit masked this other breakage, and anything git execs from git-core
(as opposed to being buitin) has never worked in the OSX dmg.
ORIG_GIT_EXEC_PATH="$GIT_EXEC_PATH"
export ORIG_GIT_EXEC_PATH
-GIT_EXEC_PATH="$bundle"
+GIT_EXEC_PATH="$bundle/git-core"
export GIT_EXEC_PATH
ORIG_GIT_TEMPLATE_DIR="$GIT_TEMPLATE_DIR"