Likes: Make posts with manually enabled likes still be likeable if Likes are enabled for all posts

[oskosk]

Fixes #2044

Changes proposed in this Pull Request:

• Makes the single post edit metabox not have likes forcedly unchecked when Likes are enabled for all posts.
• Replace a xor comparsion for a regular or when deciding whether to show the Likes button or not based on the metadata of the post and the global setting for Likes

Testing instructions:

1. Likes module enabled, Settings->Sharing set to likes on a per post basis
2. On a post, check the box to enable likes for that post, save.
3. Confirm likes are visible.
4. Change the setting on Settings->Sharing to enable likes for all posts.
5. View the previously likeable post.
6. Confirm you see the Likes button.
7. Edit the post and see the checkbox remains checked.

Proposed changelog entry for your changes:

Made manually enabled likes to still be likeable if Likes are enabled for all posts

[oskosk]

@kraftbj regarding the #2044 issue. Would it be expectable to have Likes enabled for all posts and still be able to disable Likes for a single post ? (The implementation on this PR does not do this currently)

[rachelmcr]

Would it be expectable to have Likes enabled for all posts and still be able to disable Likes for a single post ?

Yes, my understanding is this is the expected behavior. From the Jetpack Likes support doc:

If you’d rather, you can turn off the Like button for specific posts. When editing a post, find the Likes and Shares section near the bottom (you might have to scroll down to find it).

You can then uncheck the box to disable the “Show likes.” option for that post only. When you’ve set it, either publish or update your post to save the change.

[oskosk]

@vindl can I bother you with a review of the code here? Just pinging you because the code was introduced with #7175. The problem this PR tackles is #2044

[zinigor]

Works great, the logic is closer to what I intuitively expect from such settings.

[vindl]

@vindl can I bother you with a review of the code here? Just pinging you because the code was introduced with #7175. The problem this PR tackles is #2044

FWIW I don't remember writing this code 😄 - I probably just moved it to separate file so the similar logic can be reused for comment likes. Having said that, the changes here look fine to me.