t6000: fix a careless test library add-on.

It tried to "restore" GIT_AUTHOR_EMAIL environment variable but
the variable started out as unset, so ended up setting it to an
empty string.  This is now caught as an error.

Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/t/t6000lib.sh b/t/t6000lib.sh
index 01f796e..c6752af 100755 (executable)
--- a/t/t6000lib.sh
+++ b/t/t6000lib.sh
@@ -51,7 +51,12 @@ as_author()
 
        export GIT_AUTHOR_EMAIL="$_author"
        "$@"
-        export GIT_AUTHOR_EMAIL="$_save"
+       if test -z "$_save"
+       then
+               unset GIT_AUTHOR_EMAIL
+       else
+               export GIT_AUTHOR_EMAIL="$_save"
+       fi
 }
 
 commit_date()