Add support for multiple local classes

[erijo]

What does this PR do?

Make it possible to have multiple local classes.

A local class is set with: $ yadm config local.class cls1

More classes can be added with:

$ yadm config --add local.class cls2
$ yadm config --add local.class cls3

Any of cls1, cls2 and cls3 can be used in an alternate condition.

For templates, the existing variable yadm.class/YADM_CLASS is set to the last class (i.e. cls3) to remain compatible with how it works today and with what the following command gives: $ yadm config local.class

For the default template processor there is no explicit yadm.classes variable. Instead a yadm.class condition will check against all classes.

For the other processors, a new template variable YADM_CLASSES will be set to all classes separated by newline. For jinja2 templates a class can be checked with: {%- if "cls" in YADM_CLASSES.split("\n") %}

For esh templates the logic is a bit more complex, but it is possible to do.

TODO: no documentation has been updated. I'll update it later if this seems like a good idea.

What issues does this PR fix or reference?

• Support a host having multiple local classes? #185

Previous Behavior

Only one class was supported.

New Behavior

Multiple classes are supported.

Have tests been written for this change?

Yes

Have these commits been signed with GnuPG?

Yes

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Please review yadm's Contributing Guide for best practices.

[erijo]

@TheLocehiliosan: I've rebased this on top of latest develop.

I haven't updated the documentation since I'm not sure how it should be described (or even if). Suggestions are welcome.

[TheLocehiliosan]

@erijo - Another high quality PR 👍

This has been merged into develop, and will be part of the next release. I'll figure out the documentation.