How to use git pull with Jenkins sh steps?

Question

git pull doesn't work with Jenkins for some reason. I've updated some files on my local PC and pushed it to my Github. I can see the changes there. Then I run Jenkins build that has sh commands to pull from this repo and it says "Already up to date". Which is false as I clearly pushed new version to Github and if I go there and open up the file in my browser I can see the changes. This only happens with Jenkins running git pull because if I connect to my VM and run git pull myself it works fine and updates my files. Why does this happen?

My Jenkinsfile:

pipeline{
  agent any
  stages{
    stage("build"){
      steps{
        echo 'build'
        sh 'cd /var/atlassian/application-data/jira/scripts'
        sh 'eval "$(ssh-agent -s)"'
        sh 'ssh-add ~/.ssh/id_ed25519'
        sh 'git pull [email protected]:mightyajax/scripts.git'
      }
    }
    stage("test"){
      steps{
        echo 'test'
      }
    }
    stage("deploy"){
      steps{
        echo 'deploy'
      }
    }
  }
}

Answer 1

As far as I know, each sh '...' command in Jenkins is run through a separate /bin/sh process, so any changes to process-level environment only remain while that specific command is running.

For example, the cd in 'sh' line #1 only affects the first /bin/sh instance – as soon as that line is processed, the shell exits and all changes are lost. Line #2 is then processed in a brand new /bin/sh which inherits the original working directory from Jenkins. (So you're getting wrong results from "git pull" because you are in the wrong repository at that time.)

Similarly, when 'sh' line #2 sets some environment variables (namely SSH_AUTH_SOCK) through the eval, they are also immediately lost when the shell exits, so the subsequent 'ssh-add' doesn't know where the agent is.

Jenkins                                Interactive

jenkins                                sshd
├─ shell                               └─ shell
│  └─ cd /var/atlassian/etc               ├─ cd /var/atlassian/etc
├─ shell                                  ├─ eval $(ssh-agent)
│  └─ eval $(ssh-agent)                   ├─ ssh-add
├─ shell                                  └─ git pull
│  └─ ssh-add
└─ shell
   └─ git pull

To avoid this, run everything as a single script:

sh: 'cd /var/foo && eval $(ssh-agent) && ssh-add && git pull <url>'

You could also avoid the need for a manual cd by using the -C option telling Git to do it on its own: git -C /var/foo pull <url>.