Changes to Docker setup + moving the files to a different repository

[taniwallach]

There is a proposal to move the Docker files (and auxiliary files needed for the Docker build process) to a different repository, so that there will not be a need to download the full webwork2 repository (outside of the image being built) to build an Docker image of webwork.

See the discussions in:

• Update docker-entrypoint.sh #1681
• TO BE REPLACE: Discussions about Docker + originally hard copy fixes / extensions for WW 2.15 branch + move Docker base image to Ubuntu 18.04 LTS #972

[taniwallach]

One benefit of such a change would be that it would be easier to maintain functioning Docker files for the "prior" release (in a branch in the new repo).

Motivation: It would be nice if it were possible to easily build new Docker images of the "prior" release after a new release was made. (Not everyone is ready to update their servers soon after a new release.)

The current method where Dockerfile + docker-compose.yml depend on a branch name to get the version of webwork2 and pg using a branch name essentially means that "as is" the file (from the old release) will no longer be able to build that release (as we do create/keep branches for old versions), so there is currently simple method to do a Docker build of a prior release.

At present, the best approach I can think of (without support from the maintainers) would be to use a fork where either the main branch remained the prior release or where a branch for the prior release (or a tag at the final commit of the prior release) was added, and to modify the ENV variables in docker-compose.yml to use the fork + branch or tag as the source.

If I understand what I read in the manual page of git-clone a tag name can be used with the -b option instead of a branch name, in which case - if suitable tags were set in Git and the docker-compose.yml of the "old" release was set to use the tag names as the values of WEBWORK2_BRANCH and PG_BRANCH it should be possible to have the updated Docker files (using the tag names) continue to work to build the "old" release.

Adding such tags, creating the branch of the Docker files for the prior release and setting them to use the relevant tag names could be part of the process of making a new release.

[taniwallach]

@heiderich and I had started to consider moving the Docker files outside of webwork2 in the past and that was discussed in the thread at #972 and possibly elsewhere.

@xcompass had posted there at
#972 (comment) the reasons why Docker files are often left inside the code repository.

However, as webwork is split between webwork2, pg, and the OPL - we are already in a situation where changes in a different repository can require making changes to the Docker files. As with paired PRs for webwork2 and pg, we can try to indicate the connections between PRs to the "docker files" repo and PRs to the main code repos.

As such, and given other potential benefits, I certainly think that it makes sense to try to move everything needed for a Docker build into a different repository.