feat(provision): add env var config to bootstrap

Adds a set of environment variables one can set before running the
bootstrap script in order to modify its behaviour.

bootstrap.sh

@@ -3,13 +3,44 @@
 # This script is intended to be run with curl, i.e.
 #
 # bash <(curl -s https://raw.githubusercontent.com/eliasnorrby/dotfiles/develop/bootstrap.sh)
+#
+#
+# # Configuration
+# There are a number of environment variables you can set prior to
+# running this script in order to customize its behaviour.
+#
+# DOTFILES_VERSION: (master|develop|...)
+#   Select which branch to download a snapshot of
+# DO_MAS: (true)
+#   Enable to install Mac App Store apps. Make sure you log into the
+#   App Store app with your Apple ID first.
+# ASK_PASS: (true)
+#   Add the -K (--ask-become-pass) flag to ansible-playbook. This may
+#   or may not be needed to properly install homebrew.
+#
+# # Extended example:
+#
+# DO_MAS=true ASK_PASS=true bash <(curl -s https://raw.githubusercontent.com/eliasnorrby/dotfiles/develop/bootstrap.sh)
+#
 
 SECONDS=0
 
 if [ -z "$DOTFILES_VERSION" ] ; then
   DOTFILES_VERSION=${1:-master}
 fi
 
+ANSIBLE_TAGS='all,setup_homebrew,do_homebrew,do_packages,do_defaults,do_post_provision'
+ANSIBLE_FLAGS=''
+
+if [ "$DO_MAS" == true ]; then
+  ANSIBLE_TAGS="${ANSIBLE_TAGS},do_mas"
+fi
+
+if [ "$ASK_PASS" == true ]; then
+  # Ask for sudo password (possibly required for homebrew role)
+  ANSIBLE_FLAGS="-K"
+fi
+
 set -exo pipefail
 
 export DOTFILES_REPO="https://github.com/eliasnorrby/dotfiles"
@@ -38,7 +69,7 @@ cd _provision
 ansible-galaxy install -r requirements.yml
 
 _msg "Running the playbook..."
-ansible-playbook playbook.yml --tags 'all,setup_homebrew,do_homebrew,do_packages,do_defaults,do_post_provision' -v
+ansible-playbook playbook.yml --tags "$ANSIBLE_TAGS" "$ANSIBLE_FLAGS" -v
 
 _msg "Run post-install script..."
 cd $DOTFILES