Jenkins CI: Provide .Jenkinsfile as .drone.yml

TODO: upload package when it works.

.Jenkinsfile

@@ -0,0 +1,50 @@
+pipeline {
+    agent { label 'docker' }
+    stages {
+        stage('Build Debian package') {
+            agent {
+                docker {
+                    image 'evolix/gbp:bullseye'
+                    args '-u root --privileged -v /tmp:/tmp'
+                }
+            }
+            when {
+                branch 'debian'
+            }
+            steps {
+                script {
+                    sh 'mk-build-deps --install --remove debian/control'
+                    sh 'rm -rf source'
+                    sh "gbp clone --debian-branch=$GIT_BRANCH $GIT_URL source"
+                    sh 'cd source && git checkout $GIT_BRANCH && gbp buildpackage -us -uc'
+                }
+                archiveArtifacts allowEmptyArchive: true, artifacts: '*.gz,*.bz2,*.xz,*.deb,*.dsc,*.changes,*.buildinfo,lintian.txt'
+            }
+        }
+
+        stage('Upload Debian package') {
+            when {
+                branch 'debian'
+            }
+            steps {
+                script {
+                    sh 'echo Dummy line to remove once something actually happens.'
+                 /* No crendentials yet
+                    sh 'rsync -avP /tmp/bkctld/ droneci@pub.evolix.net:/home/droneci/bkctld/'
+                  */
+                }
+            }
+        }
+    }
+    post {
+        // Clean after build
+        always {
+            cleanWs(cleanWhenNotBuilt: false,
+                    deleteDirs: true,
+                    disableDeferredWipeout: true,
+                    notFailBuild: true,
+                    patterns: [[pattern: '.gitignore', type: 'INCLUDE'],
+                               [pattern: '.propsfile', type: 'EXCLUDE']])
+        }
+    }
+}