Fix makepot script using wp-i18n makepot

[Tug]

Address #751

#658 was a first attempt at fixing the mobile pot file generation.

Since then babel-plugin-makepot was removed from gutenberg and the official way is to use wp i18n make-pot instead. This PR updates our makepot script to use this.

Testing Instructions

• Have xgettext installed
• Run yarn makepot
• Check that ./gutenberg.pot and gutenberg-mobile.pot file were generated in the root folder
• gutenberg-mobile.pot should only contain the 4 following strings:
  • ADD BLOCK HERE
  • Move block up
  • Move block down
  • Remove content
    All other strings in ./src are already part of gutenberg.pot.

In a followup PR, we'll want to remove those 4 strings from this repository so all strings from this project are translated by the glopress gutenberg project

[koke]

• Move block up
• Move block down

Note for future: I see Gutenberg has similar labels, but they say "Move up" and "Move down". Perhaps we could reuse those.

[Tug]

Yeah good idea, let's start the conversation here in the meantime 👍
@SylvesterWilmott What do you think of those copy changes in guteneberg-mobile?

• Move block up => Move up
• Move block down => Move down
• Remove content => Remove Block

Concerning ADD BLOCK HERE I haven't found equivalent string in gutenberg. There's Add block but it doesn't convey the information that the block will be inserted in place of this message.

[SylvesterWilmott]

Actually we are using similar language in a future version of stats which allows a repositioning of blocks:

Move up
Move down
Remove from insights

In this case I would even consider simplifying:

Remove Block => Remove

[Tug]

Ok I updated the strings, now we only have ADD BLOCK HERE in gutenberg-mobile.

I feel we should still keep this yarn makepot script in here to be able to check the strings we have that are only in gb-mobile.

[Tug]

@koke not a priority but if you have some time to review this :)

[koke]

Why is the clean:gutenberg needed?

[Tug]

Because we want to avoid having source paths in the pot file for build and build-module files. I have tried to exclude those using the make-pot command but it's not very flexible so I'm not sure it's possible to do it cleanly.

[koke]

Have xgettext installed

Should we add some check to make sure xgettext is present and give a better error message if not? Is it worth mentioning in the README?

[Tug]

Should we add some check to make sure xgettext is present and give a better error message if not? Is it worth mentioning in the README?

Well in theory we could use wp i18n make-pot but it doesn't seem to support flow syntax at the moment. I think using xgettext is a hack at the moment and since the process of updating the strings in WPAndroid and WPiOS is manual I don't think it's worth spending more time on it. The goal is to actually have an empty POT file generated here and remove the need for that feature.

Let's add a better error message though 👍