Language Pack generation: not triggered when tag is created before it is marked as latest stable

[jeherve]

Steps to reproduce

1. Start with a plugin that needs updating, from version 1.0 to 1.1 for example.
2. svn ci all changes to trunk, but do not update the stable tag in trunk/readme.txt just yet
3. Edit the readme.txt file and update the Stable tag to 1.1. Save your changes.
4. svn cp all of trunk into a new directory for the 1.1 tag.
5. At this point, 1.1 is tagged.
6. Do some testing to ensure that this tagged version looks good and works well.
7. When you are satisfied with your changes, edit trunk/readme.txt to change the latest stable tag to 1.1.
8. Commit your changes.
9. At this point, the new version becomes available to users of your plugin.

This process is a bit more involved than the "standard" way of doing things:

1. svn ci all changes (including the stable tag update in readme.txt)
2. svn cp all of trunk into a new directory for the 1.1 tag.
3. The new version becomes available.

It is, however, a good way to test out the new version of the plugin before to make it available to everyone. It works well, too, except for one problem:

When doing this that way, strings are not moved from the Development version to Stable in translate.wordpress.org, and no language packs are generated.

Previous discussion on this topic:

• ​https://wordpress.slack.com/archives/C02QB8GMM/p1557412975361800

[jeherve]

I can't edit the ticket description anymore, but I should have added step 8 here.

7. When you are satisfied with your changes, edit trunk/readme.txt to change the latest stable tag to 1.1. At this point, the new version becomes available to users of your plugin.

8. Commit your changes.
9. At this point, the new version becomes available to users of your plugin.

[ocean90]

In 11013:

Plugin Directory: Run the I18N import for the stable tag if only the trunk readme has changed.

This should handle cases where a new stable tag is marked as latest without any other changes.

Fixes #5317.