* Merge Substrate master before checking Polkadot companion

* Also merge polkadot/master into the companion pr branch

* Set email and user name

* ci: fix echo sed failure

Co-authored-by: gabriel <gabriel@parity.io>

* check_polkadot.sh: use the branch matching substrate's branch if possible

* convert to grep

* update comment

* add post-build-test stage

* check status

* fix busybox shell

* renaming for consistency

* check_polkadot: move to external script

* check_polkadot: check for companion pr

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: Bastian Köcher <git@kchr.de>