Automate reference docs for commandline flags and env vars

既存の CRD リファレンス生成ワークフローと、手動で生成されている HBase のコマンドラインおよび環境変数のリファレンスページを確認します。次に、issue で説明されている build.rs と clap パーサーの統合と、operators のヘルプ出力を比較し、subcommands に個別の処理が必要かどうかも確認します。手書きの flag と環境変数の一覧を使わずに利用可能なリファレンスページを生成できる、保守しやすい生成方式を選択して実装すれば完了です。

Problem: Currently we have hand written docs in every operator about commandline flags and environment variables read by the operators. This is difficult to maintain and in some places it is already out of date. Like the CRD references, it would be good to generate this to reduce maintenance burden.

Cheapo variant A: dump the help page

The help pages of the operators actually already reference all the flags (obviously) and also most env vars (some would need to be added through clap, that is easy though). We already do this for stackablectl. It isn't pretty, the formatting is actually quite ugly.

By default the help doesn't show help for subcommands. Maybe we have to call each subcommand individually (or maybe we just show the help for run).

Slightly more involved variant B: generate man page, convert to adoc

There is https://github.com/clap-rs/clap/tree/master/clap_mangen to generate man pages from clap.

We could use pandoc to convert the man page to an adoc file:

pandoc -s -t asciidoc example.man -o example.adoc

And use that as our reference page.

This is a bit annoying to implement because the build.rs file has to include the clap parser definition too. Also I am unsure about the pandoc converted adoc page, I am not sure if the styling can be changed or how easily it can be done.

For reference (currently manually generated):
https://docs.stackable.tech/home/stable/hbase/reference/commandline-parameters/
https://docs.stackable.tech/home/stable/hbase/reference/environment-variables/