archive documentation: attributes are taken from the tree by default
archive documentation: attributes are taken from the tree by default

By default, git-archive takes attributes from the tree being archived.
People however often wonder why their attempts to affect the way how the
command archives their tree by changing .gitattributes in their work tree
fail.

Add a bit of explanatory note to tell them how to achieve what they want
to do.

Noticed-by: Francois Marier
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