t/test-lib.sh: minor readability improvements
t/test-lib.sh: minor readability improvements

Apply parameter expansion. Also use here document to save
test results instead of appending each line with ">>".

Signed-off-by: Mathias Lafeldt <040cb4e9e85a2ad4d7fdb95c42ca88daea898bc4@debugon.org>
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