Bypass default SCM checkout on agents and use explicit git checkout

Jenkinsfile

@@ -2,13 +2,29 @@
 
 pipeline {
     agent { label 'external-agent-1 || external-agent-2' }
-    options { disableConcurrentBuilds() }
+    options {
+        disableConcurrentBuilds()
+        skipDefaultCheckout(true)
+    }
     environment {
         PYENVPIPELINE_VIRTUALENV = '1'
         GIT_SSH_COMMAND = 'ssh -o StrictHostKeyChecking=accept-new'
     }
 
     stages {
+        stage('Checkout') {
+            steps {
+                sh '''
+                    if [ -d .git ]; then
+                        git remote set-url origin ssh://git@git.mandelblog.com:2222/salt/mandelstudio.git
+                        git fetch --tags --force --progress origin
+                    else
+                        git clone ssh://git@git.mandelblog.com:2222/salt/mandelstudio.git .
+                    fi
+                    git checkout -f origin/master
+                '''
+            }
+        }
         stage('Build') {
             steps {
                 sh '''