Can I augment scm in Jenkinsfile? - jenkins

Question

It's taken me ages to understand what checkout scm really means in Jenkinsfile (checkout is a function and scm is a default global variable by the way).
Now that I've understood it, I want to augment scm for example to increase the timeout for a particular checkout or to set sparseCheckoutPaths. Is this possible? If so, how?

Answer 1

For Git, checkout scm is basically equivalent to :
checkout([
$class: 'GitSCM',
branches: scm.branches,
doGenerateSubmoduleConfigurations: scm.doGenerateSubmoduleConfigurations,
extensions: scm.extensions,
userRemoteConfigs: scm.userRemoteConfigs
])
If you want to add sparse checkout to the existing scm, what you would do is something like:
checkout([
$class: 'GitSCM',
branches: scm.branches,
doGenerateSubmoduleConfigurations: scm.doGenerateSubmoduleConfigurations,
extensions: scm.extensions + [$class: 'SparseCheckoutPaths', sparseCheckoutPaths:[[$class:'SparseCheckoutPath', path:'path/to/file.xml']]],
userRemoteConfigs: scm.userRemoteConfigs
])
Even better, you can define a custom step, sparseCheckout in a shared library.
def call(scm, files) {
if (scm.class.simpleName == 'GitSCM') {
def filesAsPaths = files.collect {
[path: it]
}
return checkout([$class : 'GitSCM',
branches : scm.branches,
doGenerateSubmoduleConfigurations: scm.doGenerateSubmoduleConfigurations,
extensions : scm.extensions +
[[$class: 'SparseCheckoutPaths', sparseCheckoutPaths: filesAsPaths]],
submoduleCfg : scm.submoduleCfg,
userRemoteConfigs : scm.userRemoteConfigs
])
} else {
// fallback to checkout everything by default
return checkout(scm)
}
}
Then you call it with:
sparseCheckout(scm, ['path/to/file.xml'])

Answer 2

You can definitely customize the checkout scm command to add more flexibility. Check out this link for all of the options - https://jenkins.io/doc/pipeline/steps/workflow-scm-step/
Timeouts:
$class: CheckoutOption timeout::::
Specify a timeout (in minutes) for checkout.
This option overrides the default timeout of 10 minutes.
You can change the global git timeout via the property org.jenkinsci.plugins.gitclient.Git.timeOut (see JENKINS-11286). Note that property should be set on both master and slave to have effect (see JENKINS-22547).
Type: int
SparseCheckoutPaths:
$class: SparseCheckoutPaths
Specify the paths that you'd like to sparse checkout. This may be used for saving space (Think about a reference repository). Be sure to use a recent version of Git, at least above 1.7.10