Difference between lightweight checkout and shallow clone in Jenkins

Question

In the pipeline SCM configuration of Jenkins job builder, we have two options- lightweight checkout and shallow clone. What is the difference between these options and when do we use each option?

Answer 1

From the documentation:

Shallow clone.
Perform a shallow clone, so that git will not download the history of the project, saving time and disk space when you just want to access the latest version of a repository.

Lightweight checkout.
If selected, try to obtain the Pipeline script contents directly from the SCM without performing a full checkout. The advantage of this mode is its efficiency; however, you will not get any changelogs or polling based on the SCM. (If you use checkout scm during the build, this will populate the changelog and initialize polling.) Also build parameters will not be substituted into SCM configuration in this mode. Only selected SCM plugins support this mode.

To sum up:

• Shallow Clone is the Git feature that lets you pull down just the latest commits, not the entire repo history. So if your project has years of history, or history from thousands of commits, you can select a particular depth to pull.
• Lightweight checkout is a Jenkins capability that enables to pull a specific file from the repo, as opposed to the entire repo. So it is useful for example when fetching the Jenkinsfile from a repo because you you need only the specific file and Don't care about other SCM information.