After removed, the User-Agent shows in log like this: [debug] http.go:160 https://index.docker.io/v1/repositories/busybox/images -- HEADERS: map[User-Agent:[docker/0.11.1-dev go/go1.2.2 git-commit/8887e00-dirty kernel/3.14.3-n1 os/linux arch/amd64]] The code also moved all validation work into validVersion, to keep the main logic as clean. Docker-DCO-1.1-Signed-off-by: Derek <crq@kernel.org> (github: crquan) Upstream-commit: 42734394b0ec238c88bc3ef09454df411b8f3776 Component: engine