learning about jenkins current git commit

learning_jenkins.md

@@ -778,6 +778,19 @@ This will install a custom tool configured as such:
 
 Checking to see if a custom tool is installed follows the same pattern as any other plugin instance. (see Learning_Jenkins_Provisioning_Init_Script_Installing_Tools_Example).
 
+# Source code systems and common questions
+
+## How do I get the current git commit?
+
+there used to be `env.GIT_COMMIT` but I found it missing the other day
+
+do something like this instead
+
+    def res = checkout scm
+    env.GIT_COMMIT = res.GIT_COMMIT
+
+[Source](https://serverfault.com/a/950721)
+
 # Book Recommendations
 
   * [Jenkins 2 Up and Running](https://www.amazon.com/Jenkins-Deployment-Pipeline-Generation-Automation-dp-1491979593/dp/1491979593/ref=as_li_ss_tl?_encoding=UTF8&me=&qid=1555872327&linkCode=ll1&tag=wilcodevelsol-20&linkId=b957401def3d0944e387cddbf5d4c5d6&language=en_US)