s2i steps default to git ref "master", but not all git repositories have a master branch

[jmtd]

In the absence of an explicit ref in the step "Given s2i build...", i.e., Given s2i build https://...somerepo.../ with no using branchname suffix, the S2I steps will default to try to check out a branch named master, which may not exist in the repository.

Instead I think it should use the repository's default branch name.

We hit this (side issue) by introducing a new repository for cekit/behave tests, https://github.com/jboss-container-images/openjdk-test-applications, which has the default branch name main. This is the new default, I think, for both Git and Github. (At the time of writing this, I'm about to push a master branch to that repository as a temporary mitigation).

The culprits are

behave-test-steps/steps/s2i_steps.py

Line 14 in e92a239

def s2i_inner(context, application, path='.', env="", incremental=False, tag="master", runtime_image=""):

and

behave-test-steps/steps/s2i_steps.py

Line 59 in e92a239

def s2i_build(context, application, path='.', env="", incremental=False, tag="master", run=True, runtime_image=""):

and possibly a few other places.