Run stages using different container images

The Build/HTML stage needs the Emacs image because it uses Emacs to convert the
org files into html files. The Build/CSS stage runs in an image defined by the
Dockerfile in this repository, installing just make, npm, and lessc to convert
the less files into CSS files. And the Deploy step needs to upload using rsync
overs ssh.

Dockerfile

@@ -1,5 +1,3 @@
-FROM silex/emacs:27.1-alpine-dev
+FROM alpine:3.12
 
-RUN git clone https://github.com/cask/cask.git /usr/local/cask
+RUN apk add --no-cache make npm && npm -g install less
-ENV PATH="/usr/local/cask/bin:$PATH"
-RUN cask upgrade-cask

Jenkinsfile

@@ -1,23 +1,43 @@
 pipeline {
-    agent {
-        docker {
-            image 'silex/emacs:27.1-alpine-dev'
-            args '-u root --privileged'
-        }
-    }
-
     stages {
         stage('Build') {
-            steps {
+            parallel {
-                sh 'cask'
+                stage('HTML') {
-                sh 'make'
+                    agent {
-                stash includes: 'public/*', name: 'public_html'
+                        docker {
+                            image 'silex/emacs:27.1-alpine-dev'
+                            args '-u root --privileged'
+                        }
+                    }
+
+                    steps {
+                        sh 'cask'
+                        sh 'make html'
+                        stash includes: 'public/*', name: 'public_html'
+                    }
+                }
+
+                stage('CSS') {
+                    agent { dockerfile true }
+
+                    steps {
+                        sh 'make css'
+                        stash includes: 'public/*', name: 'public_css'
+                    }
+                }
             }
         }
 
         stage('Deploy') {
+            agent {
+                docker {
+                    image 'instrumentisto/rsync-ssh'
+                }
+            }
+
             steps {
                 unstash 'public_html'
+                unstash 'public_css'
 
                 withCredentials([file(credentialsId: 'ryuslash.org-deploy-key', variable: 'KEY_FILE')]) {
                     sh 'rsync -e "ssh -p 4511 -i $KEY_FILE" -v -c -r --delete public/ "site@ryuslash.org:public_html/"'