More thorough testing with pytest

[consideRatio]

Closes #67.

PR Status

Ready for review -> merge.

About test setup

The tests are setup by creating temporary git repositories where we copy a content. In the master branch of the temp git repo we put a test helm chart. In the gh-pages branch of the temp git repo we put a test helm chart repository containing the important index.yaml file.

Many tests work by capturing the output while running chartpress, and verifying that we find the right kind of statements in the output. It can be traces from chartpress itself, such as "Updating testchart/values.yaml with..." but also from docker such as "Successfully tagged..." or the helm package command etc.

Added functionality: local chart

The git_remote function previously updated a passed "jupyterhub/helm-chart" string to be git@github.com:jupyterhub/helm-chart.git or similar. As I wanted to run tests without external dependencies etc, I made this function support being passed a . string without updating it, which allowed me to work directly with the gh-pages branch of the git repository chartpress is running on.

This also opens up the new possibility of not creating a dedicated helm-chart repo for the helm chart.

bugfix: version bumping depending on what paths?

In this PR there is a slight change of behavior because of a bug fix.

chartpress.yaml
README.md
images/
- testimage
testchart/
- templates/
- values.yaml
- Chart.yaml

Previously, a change to this folder would give us a new version, now a change to the README.md wont. So it's not a big deal.

• For charts regarding version bumping, chartpress is considering the paths in chartpress.yaml, the helm charts folder, and chartpress.yaml, and any change to dependent images build context, Dockerfile or additional image paths.
• For images regarding version bumping, chartpress is considering the paths in chartpress.yaml, the build context, the Dockerfile, and chartpress.yaml.

[consideRatio]

UPDATE: Resolved without me understanding properly what happened.

---

The test succeeds on my computer, but when I run them on travis and I arrive at the part where I do various monkeypatching things fail without providing an non-negative returncode in the following way:

If someone has insight about what goes on here I'd be very interested. At this point in the code, we have already done various things, like used the git_repo fixture, and made multiple commits to a temp git repo in a temp directory etc. What happens for the first time in the test where it crashes like this, is that we run chartpress.main([]) for the first time. So I figure that is what causes things for some reason.

[minrk]

Woo! Super happy to see these tests getting added.

[consideRatio]

The cache issue in #68 (comment) resolved, or perhaps rather stopped messing with the rendered output that made me thing something was wrong. I added back lru_cache and and started clearing the lru_cache when it had become outdated using the .clear_cache() function.

[minrk]

This is excellent, great job!