chore(docs): docs/flags.md generation

[ivankatliarchuk]

Description

Added logic to generate docs/flags.md file with all currently supported flags.

At the moment, there are few way to find supported flags

• pull sources and run --help or similar
• pull docker image and run --help or similar
• check sources
• google the issue Documentation for supported flags and environment variables #4260
• more important not always clear where it is --traefik-disable-legacy or traefik-disable-legacy=true as well as where or not --no- case is supported or not and what the default value is

Added tests that will fail if new flag is added and docs/flag.md not re-generated

Fixes #4260

Checklist

• Unit tests updated
• End user documentation updated

[k8s-ci-robot]

Hi @ivankatliarchuk. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[mloiseleur]

That looks really interesting, thanks @ivankatliarchuk !
/ok-to-test

BTW, do you think you can connect on kubernetes slack to #external-dns channel ?

[ivankatliarchuk]

I would join k8s slack if i could ;-) 😂😂😂😂😂😂😂

[mloiseleur]

Would you please add a Makefile target that generate the markdown ?

[ivankatliarchuk]

Sure. Added. A note: Makefile contains quite few special characters that not necessary need to be there

[ivankatliarchuk]

is generate-documentation OK or generate-markdown ?

[Raffo]

Added a few comments.

I'd also ask that the folder name is adjusted as gen is pretty generic and not descriptive of its content. Maybe you can have internernal/gen/flagdocs or something similar to avoid long names? I'm open to other proposals as well.

[ivankatliarchuk]

Changed folder name to internal/gen/docs/flags.

[mloiseleur]

Would you please also add it in https://github.com/kubernetes-sigs/external-dns/blob/master/mkdocs.yml ?

Wdyt of putting it in About section, near the FAQ ?

[ivankatliarchuk]

Added

[Raffo]

/lgtm

@mloiseleur will live to you the second review and final approval.

[mloiseleur]

I thought about adding an alphabetical sort in the list, but I'm unsure if it will do good or harm, in this case.
I approve it as a first step, we can still make it evolve if needed.

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mloiseleur

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[ivankatliarchuk]

@mloiseleur Another option is not to do blanket sort, but instead add some grouping to flags first. Worth to consider swapping args parser. Kingpin is not will maintained, and it has lack of features like aliases, labels, grouping and its.