This is a long overdue companion commit that fixed git-commit
(Santi's
f8e2c54c9a17af3319e96db1d9e97ace36ae6831).
Having the temporary files in the working tree root when making
tags is not as bad because it does not involve 'git status' as
the git-commit case, but this makes things more consistent.
Signed-off-by: Junio C Hamano <junkio@cox.net>