git wrapper: add --git-dir=<path> and --bare options

git wrapper: add --git-dir=<path> and --bare options

With this, you can say

	git --bare repack -a -d

inside a bare repository, and it will actually work. While at it,
also move the --version, --help and --exec-path options to the
handle_options() function.

While at documenting the new options, also document the --paginate
option.

Signed-off-by: Johannes Schindelin <redacted>
Signed-off-by: Junio C Hamano <redacted>