Issue

I would like to checkout code at a given commit in a Pipeline but the git step only allows to use a branch.

Environment

• CloudBees CI (CloudBees Core) on modern cloud platforms - Managed Master
• CloudBees CI (CloudBees Core) on traditional platforms - Client Master
• CloudBees Jenkins Enterprise - Managed Master
• CloudBees Jenkins Platform - Client Master
• CloudBees Jenkins Distribution
• Jenkins LTS
• Git Plugin

Resolution

You can accomplish this using the generic scm step.
This steps is much more verbose that the git step but it provides access to most of the parameters of the git plugin.

The easiest way to configure it is to use the Pipeline Snippet Generator.
Please refer to Pipeline: Best Practices if you are unsure how to access the Snippet Generator.

Here is a simple example that will checkout from gitUrl at commit commitId:

node {
    checkout([
        $class: 'GitSCM', 
        branches: [[name: ${commitId}]], 
        doGenerateSubmoduleConfigurations: false, 
        extensions: [], 
        submoduleCfg: [], 
        userRemoteConfigs: [[url: ${gitUrl}]]])
    sh 'ls -al'
}

Tested product/plugin versions

Jenkins 2.176.x with Git Plugin version 3.10.0.

References