Set HOME environment variable to test trash directory and export for
selftests. This fixes the git-svn selftests with nonexistent or not
readable home, as found in at least one automated build system:
http://buildd.debian.org/fetch.cgi?&pkg=git-core&ver=1%3A1.4.2.3-2&arch=alpha&stamp=
1161537466&file=log
Signed-off-by: Gerrit Pape <pape@smarden.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>