flux diff could provide an inline diff for large configmap entries

[rombert]

Describe the bug

First of all, thanks for the rapid fixes around the flux diff and flux build commands.

I ran into a case in which I think the flux diff command could be even more useful. It is sometimes the case that configmap entries hold entire configuration files in formats like YAML or JSON. A one-line change in a large file is now shown by flux diff as a complete change of the whole key, which makes it hard to identify the exact line that has changed.

Steps to reproduce

1. Include a configmap with a single large key in a kustomization
2. Deploy the kustomization with flux
3. Make a small change to the configmap locally, without pushinf
4. Run flux diff

Expected behavior

The change should displayed inline, perhaps in the unified diff format.

Screenshots and recordings

No response

OS / Distro

openSUSE Tumbleweed

Flux version

v0.26.2

Flux check

► checking prerequisites
✔ Kubernetes 1.22.5 >=1.20.6-0
► checking controllers
✔ helm-controller: deployment ready
► ghcr.io/fluxcd/helm-controller:v0.16.0
✔ kustomize-controller: deployment ready
► ghcr.io/fluxcd/kustomize-controller:v0.20.0
✔ notification-controller: deployment ready
► ghcr.io/fluxcd/notification-controller:v0.21.0
✔ source-controller: deployment ready
► ghcr.io/fluxcd/source-controller:v0.21.1
✔ all checks passed

Git provider

No response

Container Registry provider

No response

Additional context

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[kingdonb]

We've just come across this at the Flux Bug Scrub and we're in agreement this would be a useful feature!

[souleb]

@rombert please test this and reopen if needed.

[rombert]

@souleb - is there a snapshot build I could use for testing?

[stefanprodan]

@rombert you can clone this repo then do make build then run ./bin/flux diff.

[rombert]

Thanks @souleb and @stefanprodan . I can confirm that the behaviour is much improved. I've attached a screenshot. I personally would prefer a unified diff format or some other format which trims unnecessary context, but this is good enough for now

[souleb]

Awesome! Thank you. I would like to add an unified diff format too, but it requires time to implement it. Maybe some time in the future.