restrictions on OCI Recipe builds prevent us from building an image

[Tom Haddon]

We use OCI Recipe builds to build images and publish them to dockerhub for our k8s charms. We've just had a new release of Mattermost (v5.32.1) and would like to rerun our recipe build for Mattermost (https://launchpad.net/~mattermost-charmers/charm-k8s-mattermost/+oci/mattermost/+recipe/mattermost). Normally we would do this by editing the Build-time ARG variables. It's currently set to mattermost_version=5.31.0. We would simply update this to 5.32.1 and then request a build and the image would be built for us. However, we're not currently allowed to edit the recipe, as we get the following error:

There is 1 error: Branch does not match format 'applicationversion-ubuntuversion', eg. 'v1.0-20.04'

The recipe build us configured to use lp:charm-k8s-mattermost. Having the OCI Recipe build in the same repository and branch as the charm code means we can reuse our existing review infrastructure for this, and also that there's one place to go to get the charm code and the build instructions for the image that it uses.

[Tom Haddon (mthaddon)]

After some explanation of the new approach I've been able to get this working. The extra step in our process is simply to tag a branch with a pattern following the required layout and configure the recipe to use it.

I think it's fine to close out this bug, but potentially some documentation (or a link to documentation) explaining a typical workflow could be added at the point where the error is surfaced.

In our case, as an example:

git clone lp:charm-k8s-mattermost
cd charm-k8s-mattermost
git checkout -b v5.32.1-20.04
git push lp:charm-k8s-mattermost

And then update the recipe to use refs/heads/v5.32.1-20.04.