t4008: modernise style
t4008: modernise style

Update this ancient test script to a more modern style in which the
expected result is prepared inside the body of the test that uses
it.  Also, instead of using $tree, a shell variable, throughout the
test script, create a tag that points at it, to make it easier to
manually debug the test script in its trash directory.

Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git