Special:Upload:

wfSpecialUpload
	new UploadForm
		mUpload = new UploadFrom...
	execute()
		$wgEnableUploads
		isAllowed(upload)
		isBlocked()
		wfReadOnly()
		processUpload()
			internalProcessUpload()
				wfRunHooks(UploadForm:BeforeProcessing)
				mUpload->getTitle()
					wfStripIllegalFilenameChars
					splitExtensions()
					checkFileExtension()
					Title::makeTitleSafe
				getUserPermissionsErrors(edit; upload; create)
				mUpload->verifyUpload()
					empty(mFileSize)
					getTitle()
					checkOverwrite()
					verifyFile()
						checkMacBinary()
					wfRunHooks(UploadVerification)
				if(!ignoreWarning) mUpload->checkWarnings()
				getInitialPageText()
				mUpload->performUpload()
					mLocalFile->upload()
					if(isGood() && $watch) addWatch()
					if(isGood()) wfRunHooks(UploadComplete)
					wfRunHooks(SpecialUploadComplete)

Changes:
	* "Your file will be renamed to $1" check now done on the result of 
	  Title::makeTitleSafe instead of filteredName
	* getExistWarning only really does existence checks
	* Other stuff forgotten to be documented