Issue #2713923 by NickWilde, markdorison: A Few attributes/new Attribute() calls use strings instead of array for classes

Issue #2714375 by kiamlaluno, malavya: hook_form_alter() implementations are still commented with a reference to a form builder that doesn't exist anymore

Issue #2580255 by Wim Leers: Remove (classy|seven)_library_info_alter() in favor of libraries-extend

Issue #2487025 by shellshocked59, harings_rob, rteijeiro, subhojit777, vijaycs85, ashutoshsngh, aburrows, swetashahi, mradcliffe, Wim Leers, lauriii, LewisNyman, Bojhan, DeeLay, B_man, davidhernandez, lizzjoy, lweinmeister, wizonesolutions, arh1, GenerUmali, tstoeckler: Remove contextual links in Seven

Issue #2566771 by Cottser, mortendk, jstoller, LewisNyman, mdrummond, Gints Ērglis, sqndr, Chernous_dn, Manjit.Singh, axe312, emma.maria, davidhernandez, lauriii, jaxxed, akalata: [Voltron patch] Move all remaining *.theme.css to Classy

Issue #2405057 by nlisgo, Manjit.Singh, ctraltdel, madhavvyas, avitslv, LewisNyman, emma.maria, joelpittet, dernetzjaeger, wmortada, karolus, cilefen, Noe_, davidhernandez, idebr: Replace arrow-asc and arrow-desc images with Libricons and implement using CSS

Issue #507488 by lauriii, mdrummond, Wim Leers, Manuel Garcia, pwolanin, davidhernandez, chx, jibran, andypost, dawehner, Xano, tuutti, Gábor Hojtsy, LewisNyman, maximiliam, eiriksm, borisson_, bill richardson, Fabianx, joelpittet, Jeff Burnz, xjm, webchick, Bojhan, EclipseGc, emma.maria, tim.plunkett: Convert page elements (local tasks, actions) into blocks

Issue #2557871 by alexpott: Remove all usages SafeMarkup::checkPlain() from template preprocess functions and attributes

Issue #2506195 by alexpott, joelpittet, xjm, David_Rothstein, Fabianx, pwolanin: Remove SafeMarkup::set() from Xss::filter()

Issue #2408463 by thomasfava, MathieuSpil, Manjit.Singh, Vidushi Mehta, LewisNyman: Rewrite entity-meta component inline with our CSS standards

Issue #2490974 by jstoller: seven_library_info_alter() is missing $extension parameter and condition

Issue #2389735 by lauriii, iMiksu, davidhernandez, larowlan, loopduplicate, LewisNyman, Wim Leers, dawehner, Cottser: Core and base theme CSS files in libraries override theme CSS files with the same name

Issue #2457887 by prateekMehta, stefan.r, rpayanm, alexpott: Use Utility\SafeMarkup class instead of Utility\String for placeholder(), checkPlain(),format() functions

Issue #2384481 follow-up by larowlan: [HEAD BROKEN] Fix references to node type properties in Seven theme.

Issue #2030597 by adci_contributor, larowlan, daffie, Thomas Brekelmans, boztek, chakrapani, InternetDevels, robbertnl, basvanderheijden: Expand BlockContent and BlockContentType with methods

Issue #2382543 by rpayanm, ianthomas_uk: Remove usage of drupal_html_class() and drupal_clean_css_identifier()

git commit -m 'Issue #2377397 by Wim Leers, alexpott: Themes should use libraries, not individual stylesheets'

Issue #2234331 by mortendk, lauriii, LewisNyman, sqndr, rteijeiro, G-raph, amitgoyal: Fixed Change the body classes to follow Drupal 8 CSS standards.

Issue #2346369 by Wim Leers: Support special '#attached' variable for attaching assets in preprocess functions.

Issue #1898478 by joelpittet, Cottser, lokapujya, m1r1k, jstoller, er.pushpinderrana, duellj, organicwire, jessebeach, idflood, Jalandhar, Risse, derheap, galooph, mike.roberts, tlattimore, nadavoid, LinL, steveoliver, chakrapani, likin, killerpoke, EVIIILJ, vlad.dancer, podarok, m86 | c4rl: Menu.inc - Convert theme_ functions to Twig.

Issue #2313931 by Berdir: Merge ['controller'] with ['build_info']['callback_object'] and add a method for it.

Issue #2301317 by pwolanin, dawehner, Wim Leers, effulgentsia, YesCT, xjm, alexpott: MenuLinkNG part4: Conversion.

Revert "Issue #2301317 by pwolanin, effulgentsia, Wim Leers, dawehner, alexpott: MenuLinkNG part4: Conversion."

This reverts commit fd2db9cd.

Issue #2301317 by pwolanin, effulgentsia, Wim Leers, dawehner, alexpott: MenuLinkNG part4: Conversion.

Issue #2073811 by dawehner, pwolanin, joelpittet, Cottser, Mark Carver, steveoliver: Add a url generator twig extension.

Issue #2300313 by blueminds: Fixed Seven theme competely overrides the $form['#attached'] on node form.

Issue #1987424 by rteijeiro, oshelach, a-fro, JeroenT, joelpittet, Cottser, IshaDakota, InternetDevels, TommyK, Sutharsan, robmc, mark.labrecque, lokapujya, Gaelan, drupalninja99, Carolyn, jenlampton, longwave: Seven.theme - Convert theme_ functions to Twig.

Issue #1912610 by amitgoyal, BryanCGreen24, lokapujya, Rajendar Reddy, echoz, barraponto, LewisNyman, pixelwhip: Rename layout classes to follow the layout style naming convention.

Issue #2089331 by grom358 | thedavidmeister: [meta] Replace calls to check_plain() with Drupal\Component\Utility\String::checkPlain().

Issue #1920862 by martin107, Mixologic, cilefen, larowlan, xan.ps, tim.plunkett | sun: Rename custom_block.module to block_content.module.

Issue #2089433 by ianthomas_uk, grom358, herom, thedavidmeister, visabhishek, longwave, Sweetchuck: Remove uses of deprecated XSS filter functions.