enable incremental compilation for beta users

services/web/app/coffee/Features/Compile/ClsiManager.coffee

@@ -124,7 +124,7 @@ module.exports = ClsiManager =
 			if project.compiler not in ClsiManager.VALID_COMPILERS
 				project.compiler = "pdflatex"
 
-			if options.syncType? # new way, either incremental or full
+			if options.incremental or options.syncType? # new way, either incremental or full
 				ClsiManager.getContentFromDocUpdaterIfMatch project_id, project, (error, projectStateHash, docUpdaterDocs) ->
 					return callback(error) if error?
 					logger.log project_id: project_id, projectStateHash: projectStateHash, docs: docUpdaterDocs?, "checked project state"

services/web/app/coffee/Features/Compile/CompileController.coffee

@@ -30,6 +30,8 @@ module.exports = CompileController =
 			options.draft = req.body.draft
 		if req.body?.check in ['validate', 'error', 'silent']
 			options.check = req.body.check
+		if req.body?.incremental
+			options.incremental = true
 		logger.log {options:options, project_id:project_id, user_id:user_id}, "got compile request"
 		CompileManager.compile project_id, user_id, options, (error, status, outputFiles, clsiServerId, limits, validationProblems) ->
 			return next(error) if error?

services/web/app/views/beta_program/opt_in.pug

@@ -18,7 +18,7 @@ block content
 											| #{translate("beta_program_badge_description")}
 											span.beta-feature-badge
 										p.text-centered
-											strong We're not currently testing anything in beta, but keep checking back!
+											strong We're currently testing lower latency compilation features in beta.
 								.row.text-centered
 									.col-md-12
 										if user.betaProgram

services/web/public/coffee/ide/pdf/controllers/PdfController.coffee

@@ -105,6 +105,7 @@ define [
 				rootDoc_id: options.rootDocOverride_id or null
 				draft: $scope.draft
 				check: checkType
+				incremental: window.user?.betaProgram
 				_csrf: window.csrfToken
 			}, {params: params}