Re-add install_themes_tabs filter

[ghost1227]

As I discussed with Andrew in Chicago, while the install_themes_tabs and install_plugins_tabs filters aren't necessarily common use, they do have uses. One of my most-used plugins actually depends on them. As the new theme installation page (and likely the upcoming rework of the plugin installation page) no longer provide these filters (and with good reason), I propose reworking the filters such that rather than the menubar being filterable, the add-new-h2 buttons take their place. The proposed patch implements this change for the themes page, and suits the needs I have for such a filter quite nicely.

[nacin]

By Andrew he means me.

[ghost1227]

By Andrew... I DO mean you ;) I firmly believe in fixing my own bugs!

[SergeyBiryukov]

1. The patch should keep the context on 'Browse' string: _x( 'Browse', 'themes' ) vs. __( 'Browse' ).
2. ​Filter docs are needed. Since WP_Theme_Install_List_Table is no longer used, I'd suggest copying the docblock​ from there (with updated defaults) and replacing it with a ​duplicate hook comment there.

[ghost1227]

Can do! Lemme finish what I'm working on, and I'll resub.

[helen]

Related, as another dropped filter in themes: #26930

[ghost1227]

I can review the linked patch when I update this one if you'd like, but since a patch is provided...

[helen]

Separate patch and ticket, just cross-referencing.

[ghost1227]

In fairness, me and Andrew are probably the only ones who've ever USED this filter, so I can't really blame anyone for removing it. But I want it back! :P

[SergeyBiryukov]

I was also thinking whether we should introduce a new filter instead of repurposing the old one. But it looks like these links are used in the same way the old tabs were used, and have a similar structure, so I guess it makes sense to reinstate the filter.

[ghost1227]

I put a lot of thought into that, but the implementation ends up being roughly the same. As such, any other plugins that may happen to utilize this filter won't need much tweaking to be updated for this implementation... as such, I chose to leave the name the same.

[DrewAPicture]

For what it's worth, renaming hooks is not without precedent if going that route makes it clearer what's actually filterable in the new context.

See pre_get_search_form, add_option_{$option}, and upload_post_params just to name a few.

[ghost1227]

@DrewAPicture I don't think changing the filter name would make it clearer, though someone with more core experience can certainly correct me if I'm wrong. What it DOES hasn't changed, just which tabs on that page it's applied on.

@SergeyBiryukov Little confused on one thing... it's not actually a duplicate hook, so not sure how a duplicate hook comment is relevant. The hook that it's duplicating was actually removed from core with the last update. I'm simply re-adding it in a slightly different spot.

[ghost1227]

Updated with inline docs and proper context

[DrewAPicture]

What's left here?

[ghost1227]

I could be wrong, but I think I have everything covered...

[SergeyBiryukov]

In 29002:

Reinstate 'install_themes_tabs' filter.

props ghost1227.
fixes #28578.

[nacin]

In 29634:

Plugin/Theme Uploads: New capabilities; unify UIs; ensure compatibility with old filters.

Introduce upload_plugins and upload_themes capabilities to allow blocking of plugin and theme uploads, versus the old hacky (and not secure) ways of just hiding UI tabs. These are simply meta capabilities that map to install_plugins and install_themes.

Also:

• Use the same nice design for the plugin upload screen as the theme upload screen.
• Better compatibility for the old install_themes_tabs filter added in [29002]. see #28578.
• Ensure using the install_plugins_tabs filter to remove the upload tab removes the new button.
• Use 'Add Plugins' instead of 'Install Plugins' to match 'Add Themes'.

fixes #29236.

[nacin]

The 'browse-themes' button wasn't an old tab. It's just there for UI "back" purposes. There's no need to pass it through the filter.

[DrewAPicture]

In 30772:

Tweak formatting in the DocBlock for the install_themes_tabs hook.

Props kpdesign.
See #28578.