trivial: check, if t/trash directory was successfully created

and was successfully entered. Otherwise git-init-db will create it directly
in the working directory (t/) which can be dangerous.

Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

t/test-lib.sh

@@ -195,7 +195,7 @@ test -d ../templates/blt || {
 test=trash
 rm -fr "$test"
 mkdir "$test"
-cd "$test"
+cd "$test" || error "Cannot setup test environment"
 "$GIT_EXEC_PATH/git" init-db --template=../../templates/blt/ 2>/dev/null ||
 error "cannot run git init-db -- have you built things yet?"