New Feature: add `--type=template` to `onyo get`

[aqw]

The parent issue is #673

Allow onyo get to return data about templates. The type should be called template. This issue supplants #552.

All templates already must be valid YAML files, so all template content is also queryable. This could be quite handy if someone is managing a large collection of templates.

• only template files should be considered; no directories
  • this means that one cannot query directories under the templates dir. I am comfortable with this limitation

Pseudo Keys:

• onyo.is.asset: False
• onyo.is.directory: False
• onyo.is.template: True
• onyo.is.empty: True or False depending if the template contents are empty (see #674)
• onyo.path.relative: path relative to the template directory (.onyo/templates) rather than repo root
• onyo.path.file: path relative to repo root
• onyo.path.parent: path to parent directory relative to the template directory

Tasks

• [ ] add to onyo_get
• [ ] add to onyo get
• [ ] shell completion
• [ ] help text
• [ ] tests

---

Open questions:

• should -i and -x be honored?
• should one be able to pass template files to onyo set and onyo unset? (see meta issue)

[TobiasKadelka]

All templates already must be valid YAML files, so all template content is also queryable.

Is that true? I only remember that at some point in the beginning we decided to allow any type of text file. The main use-case was "close to yaml". Additionally, while reading this now I wonder if that might mess up the idea of allowing a json based onyo repository.

It should be considered what happens for a file .onyo/templates/readme.md.

[aqw]

I had the same reaction, but it /must/ be true, because otherwise we wouldn't be able to set any keys/values into it.

Thus templates must be valid YAML.

[bpoldrack]

It should be considered what happens for a file .onyo/templates/readme.md.

If that's used as a template, it will fail. If it's not intended for that it should be .onyoignored.

The main use-case was "close to yaml".

I get were that was coming from, but it would only ever make sense, if onyo new was used interactively with --edit and no other option given (including no layering template). I don't think we should consider this. It would mean to have this thing work with exactly one command with very particular options and fail in every other usecase for a template (with quite a bit of effort in implementation to allow for it in the one usecase where it could work).