running my own git checkout script

Jenkins/master-windows-pipeline/Jenkinsfile

@@ -31,13 +31,13 @@ pipeline {
     stages {
         stage("git checkout"){
             steps {
-                git url: 'https://github.com/llvm/llvm-project.git'
-                powershell 'New-Item -ItemType Directory -Force -Path llvm-premerge-checks'
-                powershell 'New-Item -ItemType Directory -Force -Path ${TARGET_DIR}'
                 dir("llvm-premerge-checks")
                 {
                     git url: 'https://github.com/google/llvm-premerge-checks.git'
                 }
+                powershell "${SCRIPT_DIR}/git_checkout.ps1"
+                powershell 'New-Item -ItemType Directory -Force -Path llvm-premerge-checks'
+                powershell 'New-Item -ItemType Directory -Force -Path ${TARGET_DIR}'
             }            
         }
         stage('CMake') {

scripts/git_checkout.ps1

@@ -0,0 +1,26 @@
+# Copyright 2019 Google LLC
+
+# Licensed under the the Apache License v2.0 with LLVM Exceptions (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#     https://llvm.org/LICENSE.txt
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+if (Test-Path -PathType Container .git){
+    Write-Output "performing git pull..."
+    git checkout master
+    git reset --hard
+    git clean -fdx
+    git pull
+    # TODO: in case of errors: delete folder and clone
+} else {
+    Write-Output "performing git clone..."
+    git clone --depth 1 https://github.com/llvm/llvm-project
+}