The CI script goes looking for the branch to which a commit was pushed,
but was applying the branch name to moby/buildkit even if being built on
a different fork.
Signed-off-by: Paul "TBBle" Hampson <Paul.Hampson@Pobox.com>
This file is consumed by both validate-vendor (inside an Alpine-based
Docker container where bash is not installed), and the other scripts.
Apart from validate-vendor, all the other scripts in hack/ use bash.
Fixes CI logging a complaint:
> ./hack/validate-vendor: 31: [: pull_request: unexpected operator
Signed-off-by: Paul "TBBle" Hampson <Paul.Hampson@Pobox.com>
