Currently there is around 90 files directly under includes/ and range from TemplateParser to DummyLinker to BadFileLookup. This doesn't make a great developer experience and can be overwhelming to people who are new to mediawiki.
See the parent ticket for the suggested moves.
To move:
[ ] includes/ExtensionInfo.php
[ ] includes/GitInfo.php
[ ] includes/NoLocalSettings.php
[ ] includes/OutputHandler.php
[ ] includes/OutputPage.php
[ ] includes/SiteConfiguration.php
[ ] includes/Status.php
[ ] includes/StreamFile.php
[ ] includes/WebRequest.php
To remove:
[ ] includes/Hooks.php: Deprecated since 1.35, to be removed (T335536)
Done:
[x] includes/ActorMigration.php
[x] includes/ActorMigrationBase.php
[x] includes/BadFileLookup.php
[x] includes/CategoriesRdf.php
[x] includes/Category.php
[x] includes/CategoryViewer.php
[x] includes/CommentStore.php
[x] includes/CommentStoreComment.php
[x] includes/ConfiguredReadOnlyMode.php
[x] includes/ContentSecurityPolicy.php
[x] includes/DeprecatedGlobal.php
[x] includes/DerivativeRequest.php
[x] includes/DummyLinker.php
[x] includes/EditPage.php
[x] includes/Emptiable.php
[x] includes/FauxRequest.php
[x] includes/FauxRequestUpload.php
[x] includes/FauxResponse.php
[x] includes/FileDeleteForm.php
[x] includes/ForeignResourceManager.php
[x] includes/FormOptions.php
[x] includes/HeaderCallback.php
[x] includes/Html.php
[x] includes/HtmlHelper.php
[x] includes/LinkFilter.php
[x] includes/Linker.php
[x] includes/ListToggle.php
[x] includes/MagicWord.php
[x] includes/MagicWordArray.php
[x] includes/MagicWordFactory.php
[x] includes/MediaWikiVersionFetcher.php
[x] includes/MergeHistory.php
[x] includes/MovePage.php
[x] includes/PageProps.php
[x] includes/PathRouter.php
[x] includes/ProtectionForm.php
[x] includes/RawMessage.php
[x] includes/ReadOnlyMode.php
[x] includes/StubGlobalUser.php
[x] includes/StubObject.php
[x] includes/StubUserLang.php
[x] includes/TemplateParser.php
[x] includes/TemplatesOnThisPageFormatter.php
[x] includes/Title.php
[x] includes/TitleArray.php
[x] includes/TitleArrayFromResult.php
[x] includes/TitleFactory.php
[x] includes/TrackingCategories.php
[x] includes/WebRequestUpload.php
[x] includes/WebResponse.php
[x] includes/WikiMap.php
[x] includes/WikiReference.php
[x] includes/config-merge-strategies.php
[x] includes/config-vars.php
[x] includes/SiteStats.php
[x] includes/SiteStatsInit.php
[x] includes/Pingback.php
[x] includes/EventRelayerGroup.php
[x] includes/ProxyLookup.php
[x] includes/MWTimestamp.php
Won't be done:
[ ] ~~includes/AutoLoader.php~~ Core wiring
[ ] ~~includes/BootstrapHelperFunctions.php~~ Core wiring
[ ] ~~includes/DefaultSettings.php~~ Core wiring
[ ] ~~includes/Defines.php~~ Core wiring
[ ] ~~includes/DevelopmentSettings.php~~ Core wiring
[ ] ~~includes/GlobalFunctions.php~~ Core wiring
[ ] ~~includes/MainConfigNames.php~~ Core wiring
[ ] ~~includes/MainConfigSchema.php~~ Core wiring
[ ] ~~includes/MediaWiki.php~~ Core wiring
[ ] ~~includes/MediaWikiServices.php~~ Core wiring
[ ] ~~includes/PHPVersionCheck.php~~ Core wiring
[ ] ~~includes/PlatformSettings.php~~ Core wiring
[ ] ~~includes/ServiceWiring.php~~ Core wiring
[ ] ~~includes/Setup.php~~ Core wiring
[ ] ~~includes/SetupDynamicConfig.php~~ Core wiring (Split of Setup.php)
[ ] ~~includes/WebStart.php~~ Core wiring
[ ] ~~includes/config-schema.php~~ Core wiring