Makefile: site-offline target.

Makefile

@@ -39,14 +39,17 @@ endif
 ## I. Commands for both workshop and lesson websites
 ## =================================================
 
-.PHONY: site docker-serve repo-check clean clean-rmd
+.PHONY: site site-offline docker-serve repo-check clean clean-rmd
 
 ## * serve            : render website and run a local server
 serve : lesson-md .vendor/bundle index.md
 	@bundle exec jekyll serve
 
 ## * site             : build website but do not run a server
-site : lesson-md .vendor/bundle index.md
+site : update-bundle site-offline
+
+## * site-offline     : same as 'site' but doesn't update Ruby gems
+site-offline : lesson-md .vendor/bundle index.md
 	@bundle exec jekyll build
 
 ## * docker-serve     : use Docker to serve the site
@@ -183,6 +186,7 @@ bundle : .vendor/bundle
 ifeq (, $(BUNDLE))
 	$(error Please install Bundler using 'gem install bundler')
 else
+	$(info Installing Ruby gems)
 	@bundle config set --local path '.vendor/bundle'
 	@bundle install
 	@touch .vendor/bundle
@@ -193,8 +197,9 @@ update-bundle : Gemfile.lock
 ifeq (, $(BUNDLE))
 	$(error Please install Bundler using 'gem install bundler')
 else
+	$(info Updating Ruby gems)
 	@bundle config set --local path '.vendor/bundle'
-	@bundle update github-pages
+	@bundle update --quiet
 	@touch .vendor/bundle
 endif