Allows inception.sh to checkout custom env tag

[joehakimrahme]

inception.sh retrieves a git repo for env configuration and checks out the tag corresponding to the $release variable. This makes it difficult to use the upstream openstack-yaml-env-3nodes.git repo when deploying outside the CI.

This patch should allow the inception deployer to specify a custom tag, defaulting to $release for backwards compatibility

[joehakimrahme]

I'm not sure this is the best way to do this, but I want to start a conversation about it, as I know I'm not the only one running into issues.

For clarification, I'll give a concrete example:

If I want to deploy I.1.2.1 outside the CI, I need to create a new deployment file in my env repository, commit it and tag this commit with the release name. However, if I'm using upstream openstack-yaml-env-3nodes.git, the tag I.1.2.1 already exists (on a prior commit that doesn't contain my new deployment file).

Available options today:

• Move the tag locally to a more recent commit containing my new file. This would make the local repo out of sync with the upstream.
• Not using openstack-yaml-env-3nodes at all, and start a repo from scratch locally. This would be costly time-wise.

This patch is about giving the option to create a new tag, whose name would be different than the $release. For backward compatibility with existing scripts, it introduces a new command line argument that defaults to $release in case of its absence.

Note: the scripts would have too many positional arguments, should we maybe consider doing something with getopts?

[fredericlepied]

I don't understand why you need this change as the release variable is already the tag used to do the deployment and it can also be the branch you want to use.