Fix test-notify for systems without or with a different version of diffstat.
Some diffstat versions say "1 file changed", others "1 files changed".
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
abort: Permission denied: test-ro-message/b/vehicle