Add plugin and theme command

[swissspidy]

This fixes #24 (originally wp-cli/wp-cli#3782).

Things that still needs to be done/decided, among others:

• Decide whether wp language plugin install hello-dolly en_GB would accept an --activate flag.
  Activating a language is a global action per site. One cannot activate language X for plugin A and language Y for plugin B. Hence, I think only the core command should allow activating languages. The answer is no. Activating a language should be separate.
• Implement uninstall commands.
  \WP_CLI\CommandWithTranslation::uninstall() currently respects the object type, but doesn't know about the plugin/theme slug.
• Implement update commands.
  \WP_CLI\CommandWithTranslation::update() currently updates all translations.
  Should wp language core update only update translations for core and wp language plugin update for plugins (or a specific plugin?).
  The answer is yes. If someone wants to update all files, they can use something like for type in core plugin theme; do wp language $type update; done

[schlessera]

Decide whether wp language plugin install hello-dolly en_GB would accept an --activate flag.

Shouldn't we rather have a wp site switch-language or wp language switch instead? I also think that switch is a better term, as activating one automatically deactivates the previous one.

Implement uninstall commands.

Yes, that would be useful. Maybe we should also add a sort of --prune switch, that uninstall all non-active languages.

Implement update commands.
Should wp language core update only update translations for core and wp language plugin update for plugins (or a specific plugin?).

Yes, I still maintain that WP-CLI should be completely explicit about what it does and what it doesn't do.

[swissspidy]

Shouldn't we rather have a wp site switch-language or wp language switch instead? I also think that switch is a better term, as activating one automatically deactivates the previous one.

This sounds reasonable and I think can be worked on in a separate PR. I'll create a new issue for this.

Maybe we should also add a sort of --prune switch, that uninstall all non-active languages.

I think I'll create a separate issue for this as well.

Yes, I still maintain that WP-CLI should be completely explicit about what it does and what it doesn't do.

This would result in the following commands:

• wp language core update
• wp language plugin update
• wp language theme update

What about one command that does all of the above, e.g. wp language update-all? Like wp language core update currently does.

[swissspidy]

Looks like the cache for plugin and theme languages isn't working. Ugh.

[gitlost]

Great progress on this @swissspidy !

I'm going to take the liberty of pushing:

Update test framework to latest.

Use ja instead of en_NZ for compat with old WP versions in language-core.feature and remove refs to az as not needed and confusing, ar suffices. (These pre-date this PR.)

Add test for core update by restricting to one Travis job and using Scenario Outline to iterate over WP versions. This can be used as a template for testing plugin update and theme update as well (hopefully, if it works!).

Fix CommandWithTranslation::update() to append updates so tests pass.

Just on the dry-run message 'Available %d translations updates:', which pre-dates this PR, we should be able to come up with something nicer than that!

[schlessera]

Create a new issue for the dry run message discussion: #25